Extreme circumstances The UK’s new nuclear warhead in context Extreme circumstances The UK’s new nuclear warhead in context David Cullen Nuclear Information Service August 2022 Front cover image: Timelapse of MIRV re-entry paths from a 1986 Peacekeeper missile test. Credit: US DOD. 1 2 Contents Executive summary 4 Introduction 8 1. Background and historical context 11 US-UK nuclear cooperation 11 UK Trident warhead 11 Warhead development without live nuclear testing 12 Mark 4A upgrade 13 UK warhead stockpile figures 1998–2015 13 Low-yield capability 15 US Interoperable Warheads and the 3+2 plan 18 2. Current developments 20 W93 Warhead and other US developments 20 Nuclear Warhead Capability Sustainment Programme 23 UK Replacement Warhead Programme 25 3. US and UK nuclear policy changes 27 The 2018 US Nuclear Posture Review 27 The UK’s 2021 Integrated Review 28 4. Analysis 31 Janus-faced: nuclear-armed states under the NPT 31 UK nuclear policy under the Integrated Review 33 W93: purpose, genesis and characteristics 38 UK Replacement Warhead 44 5. Conclusions and recommendations 48 Annexes 52 Endnotes 57 Glossary 70 Acknowledgements 71 3 Executive summary Introduction In September 2020 the government announced that The United Kingdom (UK) Government’s programme the Atomic Weapons Establishment (AWE), where the to build a new nuclear warhead is the latest stage in UK’s nuclear warheads are designed and produced, the Ministry of Defence plan to replace all three parts was being brought back into public ownership. This of the UK’s nuclear weapon system: the submarine, was partly due to the poor value for money, regulatory missile and warhead. The new warhead will be and programme delivery performance under the deployed on the UK’s Trident missiles which are previous contract, but the government’s desire to leased from the United States (US). It will be a ‘parallel’ exercise greater control over AWE as the warhead programme to the new US W93 Trident warhead project commenced was also a major factor. currently being developed. W93 and Mk7 The UK is unique amongst the nine nuclear-armed The US W93 programme was revealed by the Trump states in fielding a single nuclear weapons system, administration in February 2020. The warhead using only submarine-launched missiles with no will be housed within the Mk7 aeroshell, which is ground or air-launched weapons. It has the smallest designed to protect the warhead as it re-enters earth’s nuclear weapons stockpile amongst the five nuclear- atmosphere. The Mk7 has a separate budget, and is run armed states recognised by the 1968 Nuclear Non- as a separate, but closely related, project alongside the Proliferation Treaty (NPT). As a party to that treaty the W93. UK is committed to eliminating its nuclear weapons. In March 2021 the government abandoned plans to In Fiscal Year 2021 the project entered an initial reduce the UK’s warhead stockpile limit to 180 and phase where a range of potential warhead designs instead announced an increase to 260, a reversal of are evaluated against various desired attributes, trends established towards the end of the Cold War. characteristics and constraints. After this it will transition into a second phase where the warhead This report investigates the current status of the concepts will be reviewed and developed into a series UK’s Replacement Warhead Programme to try and of design options that will eventually be winnowed understand why it is going ahead, what strategic down to a single proposed design. The current thinking underlies the decision, and what can be planning estimate cost for the W93 is $13.4bn to inferred about its likely characteristics from all $15.5bn, equivalent to between £10.9bn and £12.6bn. available sources. Much of the key source material is This figure is expected to change as the design comprised of US public documents about the W93 and matures. related programmes. The two factors that appear to have played a significant UK Replacement Warhead Programme role in the decision to build the W93 are an ambition The new warhead programme was announced in to revitalise the US nuclear weapons industrial base, February 2020. It entered its ‘readiness phase’ in the and the desire for an additional type of submarine- financial year 2019-20, and the government spent launched warhead in case of a technical problem in £214m on the project up to the end of financial year one of the two current designs. 2020-21. The project is currently at a stage analogous to the first phase of the W93 programme and is yet to Active US-UK cooperation on this new generation settle on a single chosen design. The government has of nuclear weapons pre-dates the February 2020 not provided an official cost estimate and timetable announcements of the W93 and UK replacement for the project, but the warhead is likely to come into warhead. Since 2016 the two countries have service some time in the late 2030s or early 2040s. been working together on the Joint Technology 4 Demonstrator (JTD) project, developing demonstration with substantial increases in warhead numbers in warhead systems that could potentially be deployed in 2019 and 2020. The possibility that the stockpile rose a number of future warheads. above the government’s self-imposed stockpile limit of 225 during 2020 cannot be ruled out. These increases The UK’s 2021 Integrated Review call into question public assurances that the previous The most significant change to the UK’s nuclear reductions were irreversible. posture in the 2021 Integrated Review (IR) of Security, Defence, Development and Foreign Policy was a The UK appears to be in breach of several of its reversal of a decades-long trend of reductions in the commitments under the NPT, including commitments UK nuclear stockpile. Instead of the planned reduction to unilaterally reduce its nuclear arsenal, to of the stockpile ceiling from 225 to 180 by the mid increase transparency and that reductions would be 2020s, it was increased to 260. The IR also reversed the irreversible. policy of providing information about the numbers of operational warheads and the number of deployed UK Replacement Warhead characteristics warheads and submarines. The UK Replacement Warhead is very unlikely to differ substantially from the design of the US W93 These changes will allow the number of deployed warhead. The UK warhead will depend on US-made warheads to increase with no accountability or components and will need to have an identical democratic challenge. There are two broad goals that weight distribution and shape to the W93. The UK this could be intended to achieve: either to increase the could incur substantial additional costs to produce a overall number of warheads that would be used in a warhead that would be considered less reliable, due full nuclear strike, or to increase the range of different to the difficulties in providing assurance that all the strike options available by fielding missiles carrying components would work as intended throughout the different numbers of warheads. Some missiles could life of the warhead. also potentially be carrying a lower-yield version of the warhead. Unless the difficult decision is taken for the two designs to diverge, the Replacement Warhead is The most likely explanation for this decision is a likely to follow the W93 in having an explosive yield change in what the government determines to be somewhere between the two current US strategic ‘credible’ in terms of its nuclear capabilities. While the Trident warheads: the 100kt W76-1 and the 455kt W88. process of devising the IR will have involved detailed The yield is unlikely to be as high as the W88 due to and careful analysis, that does not mean the final the increase in the accuracy of the system since that decision, taken by the Prime Minister, would have warhead was designed, but this report argues that the been characterised by careful deliberation. Suggestions new UK warhead can be expected to have a yield that that the decision was driven by a desire for the UK is significantly higher than the current UK warhead, to be more assertive about its nuclear weapons which is based on the US W76-1 warhead and thought possession are more convincing than the justifications to have a similar explosive yield. given in the IR. Evidence presented in this report also suggests a Analysis of convoys carrying nuclear warheads from lower-yield capability will be available from the new AWE to Scotland, where the UK’s nuclear-armed warhead. Part of the initial production run for the new submarines are based, suggest that warhead numbers UK warhead could even be adapted to explode with were reduced by around 12 between 2010 and 2015, this lower yield. It is also likely the design process then returned to their 2010 levels around 2017 or 2018, 5 will anticipate the warhead being hosted on missiles The need for negotiated disarmament agreements carrying different numbers of warheads, allowing for a to reduce international tensions is greater than range of strike sizes. at any time since the end of the Cold War. Recent developments have diminished the prospects for The UK replacement warhead will be based on existing international cooperation, but the stark reality of US warhead designs that have been tested, although it the alternatives means that the nuclear-armed states may incorporate elements from more than one design. have to find the political will to advance towards their Some of the warhead’s components will be based on shared objective of a world without nuclear weapons. those already used in existing US nuclear weapons. That goal is as relevant and urgent as it has ever been. The UK warhead will be housed in the Mk7 re-entry body, supplied by the US, and is almost certain to From being the NPT nuclear-weapon state that could incorporate technologies being developed under the claim to be the closest towards achieving disarmament, JTD project to increase safety and security. the UK is developing a new weapon that will likely have a larger explosive yield, and is now increasing warhead The warhead will be designed to work with the current numbers and broadening the circumstances in which Trident missile stock. The missile has been upgraded it would countenance a role for nuclear weapons in its once and is now planned to undergo a second life- security doctrine. While the internal processes that lead extension upgrade. It is very likely that the future to these decision will have involved detailed deliberation, capabilities of the missile will be taken into account the final decision by the Prime Minister appears to have during the warhead design process. been guided by a desire for the UK to be less ‘apologetic’ about its continued possession of nuclear weapons. Conclusions Although both the W93 and UK Replacement Warhead The increase in the UK’s warhead stockpile and are yet to reach the stage of selecting a final design, the probable increase in capabilities from the UK key decisions are happening now, in a political context Replacement Warhead are likely to further weaken the where the security doctrines of each country are NPT treaty regime which is already struggling with willing to countenance a widened role for nuclear a loss of credibility, and with accusations of bad faith weapons. The impact of this may prove to be long- levelled at the nuclear weapon states. As the programmes lasting, as the warheads are likely to remain in service are at an early stage in development, these harms can well into the second half of the 21st century. be avoided with sufficient political will and leadership. Specifically, the UK should declare that the new warhead This report makes the case that the W93 and the UK will not involve any upgrade to its offensive capabilities. Replacement Warhead should be seen as being driven by political considerations, rather than technical The moves away from transparency and accountability factors. The major factor in the decision to go ahead in the UK militate against this outcome. The political with the warheads is the internal pressure to sustain will to make progress on disarmament is unlikely to infrastructure and capabilities within the nuclear emerge without more scrutiny of the nuclear weapons weapon programmes in both the US and UK. This is programme, which should be provided by parliament. a clear demonstration of the limitations of a model The UK would also need to exercise influence over the of disarmament whereby nuclear-armed states make US to ensure that the parallel W93 and Replacement incremental reductions in their arsenals at a pace Warhead Programmes do not jeopardise the UK’s determined by their political convenience. disarmament commitments. The slim chances of success do not absolve the UK of its disarmament obligations 6 Recommendations 1. If the UK Replacement Warhead Programme 6. The UK’s nuclear weapons programme, particularly goes ahead, despite the known drawbacks, the the Dreadnought submarine programme and the Government should make a public statement to Replacement Warhead Programme, should be the effect that the programme will not result in subject to detailed parliamentary scrutiny to ensure any change to the UK’s nuclear capabilities, and the best possible management of the public funds any changes to the warhead design will be solely being spent. A central element of this scrutiny focussed on: should be annual inquiries and reports by the a) Improvements to safety and surety. Defence Select Committee, as was the case during b) Ease of verifiable dismantlement, using lessons construction of the first generation of Trident learned in the UK’s disarmament verification submarines and warheads through the 1980s and research. early 1990s. c) Easy replacement and life-extension of components, in order to eliminate any technical pressures for new future warhead designs while the UK remains a nuclear weapons state. 2. The UK government should release a detailed justification for the recent increase to its warhead stockpile cap, in order to allow public debate about the merits of the change. 3. This justification should include a statement about the status of any lower-yield capability on the UK’s current warhead and a timetable for the permanent phase-out of this capability, in keeping with its commitments to the 2000 and 2010 NPT Review Conferences. 4. The UK should abandon its doctrine of strategic ambiguity. It has the potential to confuse decision- making in a crisis and any strategic benefit it might provide is outweighed by the harms done to democratic scrutiny, accountability and strategic stability. 5. The UK government should immediately make public the size of its operational warhead stockpile, as well as the maximum number of missiles and warheads carried on each submarine. It should commit to updating parliament on any changes to these numbers. 7 Introduction On 25th February 2020 the Secretary of State for The UK’s Trident warhead has also been upgraded Defence announced the UK Government’s programme using components designed and built by US nuclear to build a new nuclear warhead.1 The announcement weapons laboratories. The upgrade, called the Mk4A, is was largely a formality, as the existence of the thought to have begun in late 2014 or 20159 and is still programme had been revealed 12 days earlier by ongoing. While the Mk4A involved the replacement Admiral Charles Richard, commander of U.S. Strategic of key warhead components, the overall design and Command, attracting substantial media interest.2 layout of the weapon remains largely unchanged. In The revelation was included in written testimony contrast, the UK’s Replacement Warhead will be a submitted by Admiral Richard to the US Senate new design, built with new components. This does Committee on Armed Services about the proposed not mean it will necessarily be radically different new US warhead known as the W93, which will be a from previous designs fielded by the US or UK, for ‘parallel’ programme to the UK’s new warhead.3 reasons explored in this report. Instead it is likely to be a development of previous designs, possibly This report investigates the current status of the UK’s incorporating elements from more than one. Replacement Warhead Programme and attempts to understand why it is going ahead, what strategic The UK is unique amongst the nine nuclear-armed thinking underlies the decision and what can be states in fielding a single nuclear weapon platform inferred about its likely characteristics from all and warhead,10 and has the smallest nuclear weapon available sources. Given the relationship between stockpile amongst the five nuclear-weapon states the two warheads, a thorough treatment of these recognised by the 1968 Nuclear Non-Proliferation questions requires that they first be answered in Treaty (NPT).11 The UK and the other four recognised relation to the W93. An analysis of the changes made nuclear-weapon states have committed to eliminating to UK nuclear policy under the 2021 Integrated Review their nuclear weapons and to reducing both the (IR) and the history of the lower-yield capability number of weapons they hold and the role they play in the UK’s Trident warhead are also essential for in their security policies as interim steps towards understanding the Replacement Warhead. disarmament. The UK Replacement Warhead Programme is the In March 2021 the government announced an increase latest stage in the Ministry of Defence (MOD) plan, in the UK’s warhead stockpile limit to 260, in a reversal originating in the mid-2000s, to replace all three parts of trends established towards the end of the Cold War. of the UK’s nuclear weapons system: the submarine, Combined with the overwhelming level of concerns missile and warhead.4 The current Vanguard- expressed by non-nuclear states about nuclear class submarines are being replaced with a new modernisation programmes,12 that announcement Dreadnought class. Work on these submarines began will likely exacerbate diplomatic tensions within the in March 2007,5 and the programme moved into its NPT about the failure of nuclear-weapon states to delivery phase in July 2016 following a parliamentary disarm. In 2017 these tensions led 122 states to agree vote.6 The Trident D5 missile was designed and built the Treaty on the Prohibition of Nuclear Weapons by the US for its nuclear-armed submarine (SSBN) (TPNW), which came into force in 2021 and seeks to fleet and UK missiles are leased from a common pool. conclusively establish the illegality of nuclear weapons The missile is undergoing a life extension programme in international law. in the US, with the upgraded missiles coming into service in 2017,7 most likely beginning to be loaded Given the importance of the W93 programme and the onto the UK’s submarines the same year.8 relative commitment to government transparency and accountability in the US, much of the key source 8 material for this report is comprised of US public now increasing warhead numbers and broadening the documents about the W93 and related programmes. circumstances in which it would countenance a role Public policy documents from both states are another for nuclear weapons in its security doctrine. While important source of evidence. The design specifics the internal processes that lead to these decision will and ‘missions’ of nuclear weapons are amongst the have involved detailed deliberation on the merits of most closely guarded security secrets. However, by different options, this does not mean that the final incorporating what information is in the public domain decision by the Prime Minister would have been in the context of wider US and UK policy decisions, it characterised by careful deliberation. Instead the has been possible to draw together a picture. overriding philosophy appears to be a desire for the UK to be less ‘apologetic’ about its continued possession of Some sections of the report may not initially appear to nuclear weapons. be directly relevant to the UK Replacement Warhead, but have been included as they inform analysis and In a democracy such as the UK, decisions such as conclusions in the later sections. It should be noted these should be subject to meaningful public debate that while the contents of the report are based on and informed popular consent. The degree of secrecy the best available public information, some of it is surrounding the UK’s nuclear weapons remains an necessarily speculative. obstacle to democratic oversight and public debate. By placing this information about the Replacement This report makes the case that the W93 and the UK Warhead into the public domain this report seeks to Replacement Warhead should be seen as being driven encourage a level of oversight and debate that has so by political considerations, rather than technical far been lacking. factors. The evidence suggests they are motivated primarily by an internal desire to sustain capabilities The report is divided into five parts. The first part within the UK and US nuclear enterprises, rather than provides background information that may be useful by external developments. The policy environment to readers who are less familiar with the subject of the 2018 Nuclear Posture Review (NPR) provided matter. More knowledgeable readers may wish to scope for this longstanding goal to be pursued within skip parts of this section and refer back to them as the US, but the decision was taken jointly with the UK, necessary. The second part gives an overview of with both warhead programmes being used as internal current developments in the UK and US and up-to- justification for the other in their respective countries. date information about the warhead programmes and related projects. The third part outlines the nuclear The reasons given in the US for the W93, publicly policy environment within which the programmes and within government, strongly suggest it will have been initiated. The fourth part sets out the be designed with a higher explosive yield than the argument in detail, drawing information from the current UK warhead and the W76-1, which are widely previous sections into an analysis of the UK and US understood to both have a yield of around 100kt. warhead programmes, the factors that lie behind Technical pressures mean that the UK Replacement their inception and the possible characteristics of the Warhead is very likely to follow the W93 design in warheads. The fifth part provides concluding remarks most ways, including yield. and recommendations. To aid the reader key points are provided at the beginning of the most significant From being the NPT nuclear-weapon state that sections of the report, and further technical detail has could claim to be the closest towards achieving been provided in annexes. disarmament, the UK is developing a new weapon that will likely have a larger explosive yield, and is 9 HMS Vanguard test-firing a Trident missile in 2005. 10 .LGO/dOM :tiderC 1. Background and historical context This part of the report contains contextual and from breaching the NPT prohibition on the transfer historical information that is relevant to the following of nuclear weapons. Although both countries probably sections and may be necessary for full understanding benefit from the exchange, the UK is the chief of the report contents. beneficiary due to the much greater scale and budget of the US nuclear weapons programme. The first section gives a brief history of nuclear UK Trident warhead cooperation between the UK and US before giving an overview of the UK’s Trident warhead and the techniques used for nuclear weapon design since the While technical details about the UK’s Trident end of explosive nuclear testing. It also includes the warhead, sometimes known as Holbrook,14 have never Mark 4A warhead upgrade and the changes to the UK’s been made public, it is widely believed to be close in warhead stockpile between 1998 and 2015. design to the W76. At a 1992 Defence Select Committee hearing an MOD official said it was ‘not necessarily The following sections deal with the nature of the UK’s a direct copy or based solely on the W76’.15 The two low-yield warhead capability, its relationship to the warheads are known to use different types of the high US W76-2 warhead and its role in the UK’s security explosive that is used to compress the fissile material doctrine in the early years of the UK’s Trident system. in the primary stage of the warhead to initiate a The final section in this part of the report introduces nuclear fission detonation.16 the US 3+2 warhead plan and the Integrated Warheads that were due to be produced under it. The UK appears to have begun receiving technical information about the W76 in 1980,17 around the time US-UK nuclear cooperation that the US first agreed to provide the UK with Trident missiles.18 At the time the UK’s submarine-launched Although the UK participated in the Manhattan nuclear weapons were mounted on Polaris missiles Project, which produced the first nuclear weapons that were deployed on Resolution-class submarines. in 1945, the 1946 McMahon Act put an end to US cooperation with the UK on these weapons. When Due to concerns about Soviet missile defences, and the UK subsequently started its own nuclear the vulnerability of the original UK Polaris warhead weapons programme, re-establishing the cooperative to x-rays, the UK had secretly begun work on a new relationship with the US was a major objective. Polaris warhead, known as Chevaline, in the early 1970s. Chevaline, which deployed a novel system of Following the UK’s successful test of a hydrogen decoys and penetration aids, became notorious for its bomb in 1957 the two countries signed the 1958 huge cost overruns and was only in service for 12 years. Mutual Defence Agreement (MDA), which allows for the transfer of information and materials relating A firm decision to adopt the Trident system was taken to nuclear weapon systems and military nuclear in 1980,19 and design work on the Holbrook warhead reactors.13 This treaty was supplemented by the 1963 was completed in 1987, with production beginning Polaris Sales Agreement, which provided the UK with in 1988.20 The warhead came into service when the its first submarine-launched nuclear missile system. current Vanguard submarines began to replace the Polaris fleet in 1994.21 In March 1998 the UK phased out While the transfer of assembled nuclear weapons its last WE-177 air-delivered tactical nuclear warheads, does not take place under the MDA, the two countries leaving Trident as the sole UK nuclear weapon system transfer components, fissile materials and knowledge. in service.22 This distinction is in place to prevent the agreement 11 It is widely presumed that the warhead’s full yield is so that it will re-enter the earth’s atmosphere on similar to the W76 yield of 100 kilotons.23 A kiloton (kt) a trajectory to hit the target. The shielding which refers to an explosive power equivalent to 1,000 tons protects the MIRV during re-entry is known as an of TNT. The bomb dropped on Hiroshima had a yield ‘aeroshell’, and this term is also used to refer to the of 15kt, so a 100kt blast would be around seven times whole re-entry body, as distinct from the warhead. more powerful. Warhead development without live nuclear testing Holbrook likely follows a typical modern thermonuclear design, where a boosted plutonium fission primary is compressed through implosion After signing the 1958 Mutual Defence Agreement and the energy from the primary triggers a secondary the UK had access to US nuclear test data and carried component which produces most of the yield out its own nuclear tests at the US Nevada Test Site. through a fusion reaction. These two yield-producing However, in 1993 the US signed a moratorium on components are also referred to as the ‘stages’ of the nuclear testing,25 and since then neither the UK nor warhead, and are collectively known as the ‘physics the US has carried out live nuclear tests. Instead, both package’ of the warhead. The plutonium primary is countries have invested heavily in technologies that also known as a ‘pit’. The specifics of the warhead, such allow them to continue developing warhead designs as the layout of the stages and the other components, through other experiments and simulation. The key have not been made public. techniques used are hydrodynamics, high energy laser experimentation, and computer modelling. The warhead is mounted on a submarine-launched Trident II ballistic missile. Each missile contains Hydrodynamics experiments involve capturing high- several warheads, each within its own Multiple speed x-ray images of warhead components as they Independently Targetable Re-entry Vehicle (MIRV). are subjected to high explosive force. When these Each MIRV24 can be assigned to a different target experiments involve quantities of fissile material within a large area and is manoeuvred into place below the critical mass threshold for a self-sustaining Figure 1. Data sources and modeling in nuclear weapon design without live testing26 12 nuclear reaction, they are also known as subcritical The Mk4A upgrade mirrors an upgrade to the US W76 experiments. High-energy lasers are used to simulate warhead, the W76-1. The name of the upgrade is taken the heat and energy experienced during warhead from the Mk4A re-entry body which is common to detonation. Data from these experiments and both weapons. Documents from US nuclear weapon historical data from the live testing era are integrated laboratories describe the UK Mk4A warhead as being a into computer models which then help to design British implementation of the W76-1.35 further experiments, with all three elements being interdependent.27 The relationship between the Although it is distinct in bureaucratic and budgetary different sources of data is illustrated in Figure 1. terms from the UK Dreadnought programme, the Trident life extension programmes and the UK While the UK and US run separate experimental Replacement Warhead, the Mk4A is best understood programmes, there is frequent exchange of as part of the UK’s long-term plan to replace all experimental results between them. Both countries three elements of its nuclear weapon capability. As also share information bilaterally with France, though demonstrated by its inclusion within the NWCSP, this is more limited than UK-US information sharing.28 the Mk4A was intended as a staging post on the way Cooperation between the UK and France increased to a full replacement warhead, extending the life of following the 2010 Lancaster House agreement.29 Holbrook until the new warhead is ready to come into service.36 Mark 4A upgrade UK warhead stockpile figures 1998–2015 The Mk4A upgrade to the UK warhead is part of a wider government project called the Nuclear Warhead Due to surveillance and maintenance work on the Capability Sustainment Programme (NWCSP). stockpile the actual number of nuclear warheads the Alongside the upgrade, the NWCSP has put in place UK has assembled regularly fluctuates. This variance is infrastructure deemed necessary for the Replacement likely to be higher during an upgrade programme such Warhead Programme. The wider NWCSP is discussed as the Mk4A. Official figures are expressed as a cap in more detail in a following section.30 or ceiling which the stockpile numbers are supposed to remain below, rather than the actual number at a The Mk4A upgrade extends the life of the Holbrook specific time. warhead by around 30 years,31 meaning that it will remain in service until the late 2030s or early 2040s.32 In the past the UK has published figures37 for the The Mark4A upgrade does not change the part of the overall size of its warhead stockpile and the number weapon known as the ‘physics package’ – the fusion of warheads which are operationally available. The and fission components that comprise the primary difference between the two was explained as a and secondary, although some refurbishment of ‘margin… required to allow for routine processing, these components may take place. New components maintenance and logistic management so as to include the Mk4A arming, fusing and firing system, maintain the number of operationally available the gas transfer system and new high explosives.33 The warheads at the required level.’38 This margin appears updated fuse allows more precision over the altitude to have been set at 40% of the operational stockpile of detonation and the accuracy of the weapon overall for most of the period where reliable figures exist for has been increased, meaning that the upgrade does both totals, but it would have risen to 50% of the overall increase the weapon’s capability as it is more able to stockpile, or 60 warheads, if the MOD had delivered damage hardened targets, such as bunkers.34 the reductions promised by the mid-2020s. 13 Figure 2. UK warhead numbers 1998 to 202139 pre-1998 2006 2010 2010 2015 2021 Year (actual) (actual) (actual) (planned) (actual) (planned) Operational 300 200 160 120 120 – Overall stockpile – 281 225 180 – 260 The 1998 Strategic Defence Review (SDR) said that the reduction being completed as the stockpile was the increased accuracy of Trident missiles compared upgraded to the Mk4A warhead. The SDSR also said that to Polaris meant that the number of operationally each Vanguard submarine would carry no more than 40 available warheads could be reduced to below 200, warheads and eight operational Trident missiles, and compared to the previous announced maximum the number of operationally available warheads would of 300.40 While the figure of 300 warheads was a be cut from below 160 to less than 120.45 substantial reduction compared to the peak of around 500 in the 1970s and early 1980s,41 the total number In January 2015 the MOD said that the reductions of Trident warheads produced may have been lower in operationally available warheads, missiles per than originally planned due to production difficulties submarine and warheads per missile had been during the warhead’s initial run.42 completed.46 Later that year the 2015 SDSR reaffirmed the cap of 120 operationally available warheads and The 1998 SDR also committed the UK to keeping only that the cap on the overall stockpile would reduce one submarine on patrol at a time and reducing the to 180 by the mid 2020s. The maximum of 8 Trident number of warheads per submarine to 48.43 No figure missiles per submarine was restated, and the figure was given for the overall stockpile at this time. of 40 warheads per submarine was also confirmed, however on this occasion it was presented as a simple In the 2006 White Paper the government announced total, rather than a maximum. The decision in the that the number of operationally available warheads 2021 IR to reverse these reductions is discussed in a would be cut by 20% from below 200 to below 160. A following section.47 corresponding 20% cut to the overall warhead stockpile was also announced at this time, although no figure was given for the full stockpile either before or after the cut.44 Using the 2010 figure we can infer that the cap for the full stockpile was 281 prior to the cut. This may be a nominal figure as the production problems could have prevented the stockpile from increasing to this size. The 2010 Strategic Defence and Security Review (SDSR) for the first time gave an official figure for the stockpile cap of 225 and said it would be reduced to 180 ‘by the mid 2020s’. This timeline would have meant 14 Low-yield capability The mechanism for the lower-yield option has not been made public, but the two most likely possibilities • The current UK warhead was designed with the are detonating without using tritium to boost the capability to be detonated with a lower-yield primary, or replacing the secondary with an inert, or explosion than a full detonation, probably using a ‘dud’, component. If the primary was not boosted, that variant of the warhead with a dud secondary. would have a knock-on reduction of the yield from the secondary and the fissioning of the radiation case. A • The US W76-2 warhead probably uses the same dud secondary would need to have an identical weight mechanism and is very close in design to the UK’s distribution as the component it replaced. A warhead lower-yield variant. with the option to detonate without boosting the primary could be designed so that the chosen yield • The original intent was for UK Trident submarines was selected prior to use, in a similar manner to the US to be able to deliver a range of nuclear strikes, B61 family of gravity bombs.52 using missiles carrying different numbers of warheads, some of which could detonate with a Delivering the lower-yield using a dud secondary lower-yield. This practice may have stopped by the would mean that part of the stockpile would need 2010s. to be adapted for this purpose and carried on each submarine in addition to its complement of full- yield warheads. However, it might be a more reliable Existence and mechanism approach and would represent a more efficient use As originally conceived, the UK Trident warhead was of the available nuclear materials. In theory, any not restricted to the full 100kt detonation. In 1996 thermonuclear warhead could be adapted in this way, the government confirmed that the Trident system but there may have been particular aspects of the UK included what it called a ‘sub-strategic capability’.48 Trident warhead design that facilitated this, or allowed While the existence of this capability was not treated for easy replacement of the secondary with a dud. as secret at the time, it is a seldom-discussed aspect of the warhead, and government documents have In November 1991 the last British nuclear test at the not mentioned it since the mid-2000s. However, an Nevada Test Site, known as Julin Bristol, involved the understanding of its role is important for interpreting warhead being tested at a lower yield.53 The yield of the recent changes to UK nuclear doctrine and making explosion is said to have been below 20kt.54 predictions about future plans. While the government have not publicly confirmed the In 2006 the White Paper that laid the groundwork retention of a low-yield option on the Mk4A warhead, for the replacement of the Vanguard submarine fleet in a 2007 response to the Defence Select committee elaborated that the warhead provided a lower-yield the MOD stated that they would retain the ‘flexibility’ capability.49 The following year a government response of having a low-yield option on the warhead.55 As the to the Defence Select Committee described this as ‘an NWCSP (which includes work on the Mk4A upgrade) ability to employ a reduced yield’ from the warhead.50 was in the planning stages at this time,56 it is likely Earlier, in evidence to the committee, Retired that the upgraded warhead retains the capacity to be Commodore Tim Hare, who was the MOD’s director detonated at a lower yield. of nuclear policy from 1999 to 2002, said that the lower yield option didn’t involve ‘a great deal’ in terms of configuration.51 15 US W76-2 The Government’s 2006 White Paper again claimed The development of a US low-yield submarine that the existence of a low-yield option makes the UK’s warhead was announced in the Trump nuclear forces more ‘credible’ as a deterrent.63 In his administration’s 2018 Nuclear Posture Review Defence Select Committee evidence Tim Hare said (NPR). Within a year of the NPR being published, that the sub-strategic doctrine envisages it being used the first W76-2 units were being produced,57 and full as ‘an extra option in the escalatory process’ prior to production was completed in June 2020,58 less than 18 ordering a full nuclear strike.64 months after publication. The short production run affirms official statements that a small number of The Defence Secretary in 2006, Des Browne, told W76-1 warheads were converted to the W76-2 variant.59 the select committee that a decision had been taken The short turnaround from concept to deployment to cease using the term ‘sub-strategic’, but said it suggests that the W76-2 did not require any had previously referred to ‘a limited use’ of the UK’s significant design and development time and that the nuclear weapons.65 The MOD’s response to the Select warhead components did not require any additional Committee said that retaining a low yield capability qualification or certification activities for the changed made the UK ‘more credible against the range of configuration. nuclear threats’ the UK might face.66 The fact that the W76-2 went through a production Both Browne67 and Hare emphasised that a low-yield line, and that the US elected to deliver its low-yield Trident strike would not be used to achieve military W76 through a separate warhead variant, suggests objectives, with Hare differentiating this from a that converting the warheads to W76-2 involved the ‘tactical’ usage and elaborating that the purpose was to removal or alteration of existing components. The demonstrate the willingness to employ a full nuclear lack of a protracted development phase suggests that strike against adversaries. The 2006 White Paper the US used a warhead configuration that was already stated that it was specifically intended to deter smaller certified and considered reliable. Taken together, nuclear threats.68 the evidence suggests that UK’s low-yield version of the Holbrook warhead shares a mechanism with the From the language at the time it would appear that W76-2, most likely involving a dud secondary, and UK nuclear strike options covered a range of attack confidence in the design is derived from it having been sizes from a single low-yield warhead, through a small successfully detonated in the Julin Bristol test. Sources number of warheads at their full yield, to a full strike. briefing on the W76-2 back up the supposition that the Some of the options in between these extremes would warhead has a dud secondary and suggest the yield is have involved missiles carrying different numbers around 5kt.60 Other sources suggest the yield is 8kt.61 of warheads. This interpretation has been indirectly confirmed by Michael Quinlan, Permanent Secretary Role of the low-yield capability in UK nuclear at the MOD from 1988 to 1992,69 and government doctrine answers to questions in the House of Lords in 1996 The 1998 Strategic Defence Review claimed that the confirm that at the time lower-yield and full-yield ‘credibility of deterrence’ requires the UK to retain the warheads were carried on separate missiles.70 capability of a limited nuclear strike ‘that would not automatically lead to a full scale nuclear exchange’, and The repeated references to ‘credibility’ invoke a that as the country’s sole nuclear system Trident had to hypothetical situation where an adversary might fulfil this role.62 doubt the UK’s willingness to order a full nuclear strike in response to a non-nuclear attack or a low-yield nuclear use. To prevent this, it was deemed necessary 16 HMS Victorious near Faslane. for ‘credibility’ that the UK be able to mount a range yield capability may indicate the practice had been of nuclear responses using different numbers of discontinued by the 2010s, or it may be a consequence warheads and/or the low yield option on the warhead of the decision under Browne to cease using the term to carry out a demonstrative nuclear strike on a scale sub-strategic. that would be deemed appropriate. The apparent speed at which part of the US W76 Recently archival research has confirmed both the stockpile was converted to the W76-2 variant suggests practice of missiles carrying different warhead loads that the UK could similarly convert part of its and that the lower-yield capability was delivered by warhead stockpile between lower-yield and full-yield a separate warhead variant. The revelation that the configurations with relative ease. A recent statement lower-yield warheads required less highly enriched that none of the UK’s weapons ‘are designed for uranium supports the interpretation that they tactical use during conflict’72 does not rule out some incorporated a dud secondary.71 of the stockpile being converted for use with a lower yield or the capability having been retained, given The official limit of eight operational missiles and the previous insistence that the capability was not 40 warheads per submarine, published in the 2010 intended for tactical use. The current status of the and 2015 SDSRs, would have allowed little margin for low-yield capability is discussed in the ‘Reason for the submarines to patrol with missiles carrying a range warhead stockpile increase’ section below.73 of warhead loads. The official silence on the lower- 17 .LGO/dOM:tiderC US Interoperable Warheads and the 3+2 warhead, the IW1. While the 3+2 strategy did not plan intend the three ballistic missile warheads to be direct replacements of the five existing designs, IW1 was • Between 2010 and 2018 the long term plan of the intended to replace both the W88 Trident warhead and NNSA was to rationalise its stockpile from 12 the W78 Minuteman warhead.79 warhead designs to just 5. The IW1 warhead would have consisted of a nuclear • Components from the 3 planned interoperable explosives package (NEP) that could be carried in both ballistic missile warheads would have been the Mk5 re-entry body currently used by the W88 designed to be used in various other warhead warhead and the Mk21 re-entry vehicle currently designs. used by the W87 ICBM warhead.80 Many of the IW1 components would have been designed to be easily incorporated into other 3+2 warhead designs,81 in order The W93 programme arose directly from the previous to minimise costs and simplify future manufacturing US 3+2 plan, which aimed to rationalise the US nuclear and maintenance work. weapon stockpile from 12 different types of weapon to five.74 In US Navy budget requests the project for The IW1 was authorised by the US Nuclear Weapons designing the W93 warhead and its Mk7 aeroshell Council in June 2012 and progress was accelerated in was previously known as the Interoperable Warhead Fiscal Year(FY)82 2013 so that the programme could project,75 which was to be the first warhead built under focus on a preferred design concept from an early the National Nuclear Security Administration’s (NNSA) stage. It was decided to use a primary core, or ‘pit’, 3+2 strategy. similar to the one used in the W87, but the programme timetable was then delayed for budgetary reasons The 3+2 strategy arose from the Obama and to allow the NNSA to focus on the W80-4 cruise Administration’s 2010 Nuclear Posture Review missile warhead. Under the revised timetable the IW1 and National Security Strategy. Under it, warhead First Production Unit would have been produced in programmes that were already well advanced, such FY 2030.83 The steps which led instead to the W93 as the W76-1 and W88-Alt 370 upgrades, would programme are discussed in detail below.84 continue as originally conceived.76 However, when other warheads or nuclear bombs in the stockpile came towards the end of their service lives, instead of a new life-extension programme, they would have been replaced by one of the five designs.77 The intention was to produce three interoperable ballistic missile warhead designs that could all be fielded both on Trident missiles and silo-based Minuteman II missiles, as well as one air-delivered nuclear gravity bomb and one air-launched nuclear cruise missile.78 Figure 3 shows the intended changes. The B61-12 life extension programme (LEP), while pre-dating the strategy, was intended to be the gravity bomb warhead, and the next priority for the strategy was to build the first interoperable ballistic missile 18 Figure 3. US nuclear weapon stockpile plans: Fiscal Year 2015 vs 3+2 plan85 19 2. Current developments This part of the report discusses current and recent process, the Concept and Assessment Refinement developments related to the US W93 and the UK Stage. During this initial phase a range of potential Replacement Warhead project. The early sections warhead designs are evaluated against various relate to programmes in the US that provide important desired attributes, characteristics and constraints.88 context for the UK’s Replacement Warhead: the W93 During FY2021 the respective design spaces for the and Mk7 aeroshell programmes and the justifications nuclear and non-nuclear parts of the warhead were for them. The following sections relate directly to the identified.89 UK. The NWCSP has put in place the infrastructure that will be used to build the UK Replacement The FY 2022 NNSA budget request anticipated the W93 Warhead. The Replacement Warhead Programme transitioning into Phase 2 during FY 2022, following section draws on the previous sections and sets out approval from the Nuclear Weapons Council.90 During what is currently known about the programme. Phase 2 the warhead concepts identified during Phase 1 will be reviewed and developed into a series of design W93 Warhead and other US developments options that will eventually be winnowed down to a single proposed design. Phase 2 is planned to continue • The W93 will be a new warhead design, but will during FY 2023,91 during which work will take place to be based on components that were previously live down-select the nuclear explosive package. Part of this tested work will involve a system level assessment of possible primary designs.92 • The UK is a participant in the US W93 and Mk7. programmes and probably has input into the Once a single design has been selected the programme design but no decision-making power. will proceed to Phase 2A: Design Definition and Cost Study,93 possibly in FY 2025 or 2026.94 Coordination • After a period identifying possible design with the UK Replacement Warhead Programme is an concepts, in FY 2022 the two programmes integral part of the project,95 and the UK will likely progressed towards reviewing and refining these have some input into the W93 project but no decision- concepts in order to select a single chosen design. making authority. The remaining stages of the weapons acquisition process can be seen in Figure 4. A similar 6.x process is used in life extension projects W93 and Mk7 Programmes such as the W76-1 LEP.96 The proposed W93 programme was revealed in the Trump administration’s NNSA budget request for FY The Mk 7 re-entry body which will house the W93 has 2021. After the budget was published the Pentagon a separate budget, which falls under the US Navy’s briefed that W93 will be a new warhead design. It will budget request. The Mk7 and W93 programmes are include new conventional components and additional run as separate, but closely related, projects with safety features, but will be based on existing designs synchronised timetables. The W93 Phase 1 concepts and components that are already in the stockpile. As an will inform the design requirements for the Mk7 re- example of the kind of changes that might take place, entry body97 and the two will be designed in parallel, it was suggested that the position of the secondary and as each will need to take into account aspects of primary within the warhead might be swapped.86 the other. The Mk7 design will be predicated on a specific warhead mass and weight distribution, but its The W93 NNSA budget request for FY 2021, which was dimensions and shape will also circumscribe those of approved by Congress,87 asked for funds to begin Phase the warhead. 1 of the NNSA-DOD Phase 1-7 weapons acquisition 20 Navy budget requests for the Mk7/W93 programme Figure 4. NNSA-DOD weapons acquisition in FY 2021 include the commencement of a trade process101 study for aeroshell design options and development of material for the aeroshell thermal protection system, including analysis and modelling potential materials for vulnerabilities, accuracy, reliability and performance in flight. FY 2022 plans include initial data analysis for fire control software support for the W93 and the early stages of developing material for the aeroshell, including ground testing. It is anticipated that aeroshell development will include a mock flight experiment once the programme moves into Phase 3.98 The Mk7 design will involve a new Arming, Fusing, and Firing (AF&F) subsystem and Release Assembly.99 Annexe A includes further detail on the planned outputs from the two programmes during these years. The 2022 NNSA Stockpile Stewardship and Management Plan provides a ‘planning estimate’ cost of between $13.4bn and $15.5bn for the W93. This was said to be ‘based on preliminary assumptions for the… design, with increased uncertainty’, and is expected to be revised in the future.100 Since 2016 the US and UK have been working together on new warhead technology as part of the Joint Technology Demonstrator (JTD) project. Although the JTD works on technology that is not tied to a specific new warhead design its short-term focus means that many of the technologies it develops will be utilised in the W93 and UK Replacement Warhead. Workstream 2 of the JTD is focussed on a reference warhead design based on the Mk21 aeroshell, which houses the W87 warhead. Workstream 1 was until recently focussed on a reference design based on the Mk5 aeroshell that houses the W88 warhead, but has recently transitioned away from that and its current reference design is probably based on the expected characteristics of the Mk7 aeroshell. 21 The JTD has investigated advanced manufacturing The five reasons given were: technologies and worked on enhanced surety. Surety 1. To better meet the operational requirements of in nuclear weapons design refers to measures that are US Strategic Command. This was said to have two intended to prevent the weapon being used without elements: authorisation, while ensuring it is as reliable as • According to the memo the stock of W88 possible at the time of authorised use and maximising warheads will be reduced by the W88 Alt 370 safety at all other times. Surety technologies can be programme and surveillance activities and the an internal design feature of the warhead, something resulting warhead mix will not give sufficient outside the warhead itself, or a mix of the two.102 confidence that the warheads could destroy all Outside the JTD the UK and US have carried out the targets in US war plans. research on system survivability. More detail on the • The W93’s lighter weight would allow a Trident JTD and other joint research can be found in Annexe B. missile strike from a greater distance, and over a greater spread of targets, increasing submarine Instead of replacing the Trident D5 missile the US patrol areas at a time when submarine detection now plans a second life-extension programme for capabilities are improving. the missile, known as the D5LE2. The programme is 2. To support the UK’s Replacement Warhead intended to at least match the current missile accuracy Programme. and range while being more able to counter and 3. To mitigate the risk from delays to life extension survive missile defence systems. More detail on the or replacement programmes for either the W76 or D5LE2 can be found in Annexe C. W88, which are said to be reaching the end of their service lives ‘at nearly the same time’ during the Justification ‘2030s–2040s’. In December 2020 an unpublished section of a joint 4. For the W93 to act as a technical hedge for the Pentagon and Department of Energy (DOE) memo, sea-leg of the US nuclear triad, an additional design listing justifications for the W93 programme, was that would be unaffected if a serious technical issue leaked to the Guardian newspaper.103 The memo listed were discovered in one of the other two designs, three overall factors and five more specific reasons particularly the W76. for the decision, many of which also appear in public 5. To revitalise the US nuclear industrial base, statements by US officials.104 particularly in aeroshell development.105 The three overall factors were: While the purpose of the memo is evidently to make • Changes in the ‘threat environment’, particularly the case for the decision, and it should not be taken improvements to defences in countries the US entirely at face value, its contents do give some insight considers as adversaries. into the possible reasoning behind the decision. The • The age and makeup of the US submarine-launched approach of the 2018 Nuclear Posture Review is clearly warhead stockpile. evident in several of its reasons. An analysis of these • The move to a smaller nuclear-armed submarine justifications and, the rationale behind the W93 project fleet with fewer missile tubes when the planned new and its role in the US warhead stockpile can be found Columbia-class SSBN comes into service. below.106 Alongside the available information about the W93 and related programmes, this then informs an analysis of the likely characteristics of the W93. 22 Nuclear Warhead Capability Sustainment have been used for nuclear weapon development in Programme place of live nuclear explosive testing and will be used to design the Replacement Warhead. • The NWCSP put in place the infrastructure necessary for delivering the Replacement Warhead AWE’s Orion laser facility became operational in Programme and included the Replacement Mk4A April 2013. The facility combines 10 long-pulse laser upgrade to the UK Trident warhead. beams and two petawatt short-pulse beams, creating conditions of up to 10 million degrees centigrade. • Several projects within the NWCSP related Orion was designed to complement the research directly to the technologies used to develop programme at the US National Ignition Facility.112 nuclear warheads without nuclear explosive Figure 5 shows a diagram published in 2002 testing. illustrating the range of conditions that different experiments and facilities can simulate. • Delays and cost overruns have affected some of these projects and at least one is likely to have part The ‘Orchard’ computing facility at AWE, constructed of its cost included in the Replacement Warhead under the NWCSP, will likely house the latest Programme. supercomputer purchase: a seven petaflop113 Cray Shasta supercomputer, which will be named ‘Vulcan’. The acquisition of Vulcan was announced in December The Mk4A warhead programme, as discussed above,107 2019, and it was planned to go into general production was part of the larger NWCSP. Announced in 2005,108 by the end of 2020.114 At present it has not appeared the NWCSP was intended to sustain the UK’s ability to on the most recent rankings of the most powerful produce nuclear weapons in the long term. Aside from computers in the world, but with theoretical peak delivering the Mk4A warhead upgrade, the NWCSP’s performance of 7.42 Petaflops it will be nearly twice main objectives have been to build the facilities needed as fast as AWE’s Damson supercomputer, which was for the Replacement Warhead Programme, and to built in 2017, and is currently considered to be the 156th develop and retain the skills and capability necessary most powerful computer in the world.115 for the continued production of nuclear weapons.109 In November 2010 the hydrodynamic facility planned The official start date of the NWCSP was in April under the NWCSP was cancelled in favour of a joint 2008 and it was due to run until April 2025. As well French-UK facility at Valduc in France, known as as the full running costs for the Atomic Weapons Epure. The joint project, known as Teutates, is late and Establishment (AWE) over that time, the programme over budget, although the MOD claims it is still able included numerous infrastructure projects including to be completed on time.116 The UK Government will new facilities for manufacturing high explosives, not release information on the cost of the programme conventional manufacturing and chemical and its final in-service date, saying that to do so would processing.110 The total cost of the NWCSP was harm relations with France.117 The facility appears to projected to be just below £20bn.111 currently be operational, but only able to capture data in two dimensions until the third axis for the facility is Several of the infrastructure projects relate directly to built.118 It is not clear whether this reduced capability hydrodynamics, high energy laser experimentation, will have any implications for the UK’s Replacement and computer modelling, the three techniques that Warhead timetable. 23 Figure 5. Conditions created in a nuclear warhead119 Teutates is not the only project under the NWCSP to part of the project to commence immediately with the have run into problems. The Mensa warhead assembly aim of having the manufacturing facility able to begin and disassembly facility at AWE Burghfield was until production in 2030.122 recently seven years behind schedule and expected to cost £1.8bn, nearly 2.5 times its original budget.120 The total cost of the project is expected to be higher However in February 2022 the Government admitted than the approved £634m budget. No official estimate that the completion date for Mensa had moved from of the full cost of the project has been made public. 2023 to 2024 and the project is now expected to cost The government plan to spend part of the remaining just under £2bn.121 budget on building the store and assessing the cost of completing the manufacturing facility. The cost Work on the Pegasus enriched uranium facility, also of this second stage of the Pegasus project is likely considerably delayed and over budget, was paused to be included in the budget of the Replacement for several years. The official rationale for this was to Warhead Programme, which will probably also include re-evaluate options for the project, but it is likely that additional infrastructure projects.123 a desire to limit short-term costs was a major factor. The government announced in March 2021 that work As this report was being prepared for publication, on the project was re-starting, with work on the store the Government published its annual release of data on its major projects portfolio. The NWCSP does not 24 appear on the list, but Mensa, Pegasus and Teutates replacement options’127 to ‘refin[ing] options were included as separate projects, with all project and technical solutions’ in December 2018128 and details redacted. 124 This suggests that the NWCSP, if ‘develop[ing] the evidence to support a government it still exists as a distinct government project, is not decision’ in December 2019.129 Project data released large enough to meet the threshold for being included in July 2018 listed one of the aims of the NWCSP as in the Major Projects Portfolio. Whatever the current providing evidence for the warhead decision.130 This status of the NWCSP and its subsidiary projects, work will have built on earlier studies that were carried the cost overruns and delays that have dogged it out from 2008 onwards.131 Annexe A, which details the raise questions about the ability of the UK’s nuclear outputs of the W93 and related programmes, gives an enterprise to deliver the Replacement Warhead idea of the types of documents which will be being Programme on time and to budget, particularly any produced internally since the decision to go ahead infrastructure projects that might be included. with the warhead. UK Replacement Warhead Programme The timing of the announcement fits within the timescale that had been long predicted by the • The UK Replacement Warhead Programme is at a government,132 although in 2018 the update alluded to similar stage of development to the W93 and will the timetable being dependent on US plans following currently be refining warhead design options. the NPR earlier that year.133 The most likely chain of events is that part way through 2019 US plans arising • There is no official budget and timetable for the from the NPR and the Navy Feasibility Study134 were warhead, but it is likely to come into service in the sufficiently certain for the UK to bring the warhead late 2030s or early 2040s. Using the US planning replacement project to the readiness phase, and the estimate for the W93 we can estimate a ballpark cost formal decision to go ahead was scheduled to be for the warhead of between £10.9bn and £12.6bn. taken after the announcement of the December 2019 election. Preparatory work Cost and timescale The government has made few details public since Although the Replacement Warhead Project will likely the February 2020 announcement of the Replacement use a separate programme management system from Warhead Programme. In response to parliamentary NNSA-DOD Phase 1-7 weapons acquisition process,135 questions the decision was presented as having been the development stages it will pass through will be taken by the government as a collective under the broadly similar.136 As discussed below,137 the warhead leadership of the Prime Minister.125 The government is likely to closely follow the design of the W93, but was said to have spent £116m on planning the warhead as a bare minimum it will need to fit within the Mk7 replacement to the end of financial year 2018-19, and aeroshell and have an identical weight distribution to £98m in financial years 2019-20 and 2020-21, which the W93. Due to its dependencies on both aeroshell was referred to as the ‘Replacement Warhead readiness and weapon design choices,138 and in order to feed phase’.126 into the US design processes, the Replacement Warhead Programme will need to follow the Mk7/W93 This ‘readiness phase’ was not publicly announced in timetable until the design and specifications for the the government’s annual ‘Future Nuclear Deterrent’ aeroshell are agreed. updates to parliament, but during that time the language about warhead replacement activities was changed from the previous references to ‘developing 25 In June 2021 the MoDs’ Director General Nuclear intended to come into service some time in the late commented that the project had to do a lot of work to 2030s or early 2040s. This also aligns with the estimate ‘get through those designs’.139 This confirms that the in the 2011 Trident Alternatives Review of a 17 year project was in a stage analogous to the US Concept turnaround for a new warhead.147 Assessment phase and had yet to move into something akin to the Feasibility Study and Design Options The production of the warhead is likely to be spread phase. out over a relatively long period of time. Conversion of the stockpile to Mk4A started before 2016148 and may The government says it is too early to provide cost last nearly a decade.149 Given the issues caused by long estimates for the project,140 but the Strategic Outline fallow periods in the nuclear enterprise,150 it seems Case was approved by the Cabinet Office’s Major likely this practice of extending production runs in Projects Review Group in September 2021.141 It was not order to minimise the downtime between warhead included into the Government’s Major Projects data production and upgrade cycles will continue. release in July 2022.142 This suggests that funding has only been released for the early stages of the project Renationalisation of AWE and the currently approved budget for the project is In September 2020 the government announced that not large enough to meet the threshold for including AWE, previously operated as a government owned, in the Major Projects Portfolio. If so, an official budget commercially operated enterprise, was being brought estimate is unlikely to be made public until after a back into public ownership. This was achieved by warhead design is selected. The current $13.4bn to making the MOD the sole shareholder of AWE Plc, the $15.5bn planning estimate for the W93 is equivalent to company that owns the AWE sites. between £10.9bn and £12.6bn. Given the uncertainties in the original US figures and the potential for costs NIS understands that the change was in part a differing between the two countries this should be consequence of the poor regulatory and programme regarded as a ballpark figure, rather than an accurate delivery performance of the Lockheed Martin-Serco- estimate. If infrastructure work is included within the Jacobs Engineering consortium who previously held UK warhead project, the final cost could be higher. the contract, and the poor value for money that the contract represented for the government. However, The government refused to give information about the the desire to exercise greater control over AWE as timeline of the project in response to a parliamentary the warhead project commenced was clearly also a question, citing national security.143 However, the major factor.151 AWE will be run as an arms-length likely timescale of the project can be inferred from body of the MOD. There have been some changes at information already in the public domain. The US board level, but much of the senior leadership team, W76-1 was said to extend the service life of the W76 including the chief executive Alison Atkinson who was to 60 years,144 meaning that the earliest manufactured appointed in May 2020, remain in post.152 This suggests units will expire in the late 2030s. The UK’s warheads that the decision to renationalise was motivated by were manufactured later, but may have a shorter concerns about accountability and cost rather than service life than the W76 due to the ageing of US-made dissatisfaction with management at the sites. components.145 The 2016 update to parliament said that the replacement warhead would not be needed ‘until at least the late 2030s, possibly later’146 Given that the decision to proceed with the replacement programme was broadly in line with the timetable envisaged in 2016, it would seem that the Replacement Warhead is 26 3. US and UK nuclear policy changes This part of the report deals with the policy of ‘credible’ US nuclear strike options. To this end environment surrounding the decisions to develop it announced a new low-yield submarine-launched the W93 and the UK Replacement Warhead. The first nuclear warhead, later revealed to be the W76-2. Over section looks at the US 2018 Nuclear Posture Review the longer-term the NPR also pledged to develop a new (NPR), which provided the policy environment that nuclear-armed sea-launched cruise missile.156 led to the W93 decision and informed much of the thinking that underlies its justification. The second Claims about a Russian ‘escalate to de-escalate’ section looks at the UK’s 2021 IR. Although the IR came strategy are a long-standing feature of debate in US out a year after the announcement of the Replacement nuclear policy circles. The Russian government has Warhead Programme, the two appear to be part of publicly rejected the claim and analysts are divided a single process of policy development. Due to the about whether such a strategy exists in Russian limited information we have about the two warhead nuclear doctrine.157 programmes, the policy documents of the two states provide important contextual information that enable Hedging is a major concept in the NPR. Nuclear greater understanding of the reasoning and purpose weapons are said to provide a hedge against four behind the decision. This information will be drawn categories of risk: geopolitical (the emergence of new out in part 4 of the report. adversaries, or of new capabilities or behaviour from existing adversaries), technological (both technological The 2018 US Nuclear Posture Review failure in US nuclear capabilities, or the technological developments of adversaries), operational (ranging • The 2018 NPR increased the role of nuclear from mistakes made by US forces to US intelligence weapons to deal with a greater range of threats failures), and programmatic (meaning issues within than had been the case previously. the US nuclear weapons programme, such as delays, ageing warheads or an inability to produce • The concept of hedging in the NPR is used to components).158 The NPR envisages nuclear weapons justify additional layers of redundancy in the US both reducing the risk of these issues occurring and nuclear stockpile. minimising the impact if they do occur, and says that decisions about US nuclear forces and infrastructure will be guided by this hedging strategy.159 The Trump administration’s 2018 Nuclear Posture Review (NPR) enlarged the role of nuclear weapons in This expansive conception of hedging found in the US doctrine to include the deterrence of non-nuclear 2018 NPR goes beyond how the term has been used in threats, including ‘chemical, biological, cyber, and the past. Introduced in the 1994 NPR under the Clinton large-scale conventional aggression’.153 It stated there administration, the application of the term changed was ‘no ‘one size fits all’ for deterrence’, meaning in both the 2002 Bush administration and the 2010 ‘a tailored and flexible approach’ was needed to Obama administration NPRs, but of the four categories ‘effectively deter across a spectrum of adversaries, of risk in the 2018 NPR it was applied only to some threats and contexts.’154 In practice this was said to aspects of geopolitical and technological risk.160 As can require an increasing ‘diversity and flexibility of be seen from the joint Pentagon and DOE memo, this platforms, weapons and modes of operations’.155 concept of hedging is used to justify additional layers of redundancy within the US nuclear stockpile. The The review claimed that in order to counteract a memo justifies the W93 as an additional hedge within supposed Russian ‘escalate to de-escalate’ strategy it the submarine leg of the triad, should a problem arise was necessary to increase the ‘flexibility and range’ 27 in one of the SLBM warheads, whereas in the 1994 In March 2021 the UK released its Integrated Review conception, the three legs of the triad are considered of Security, Defence, Development and Foreign Policy, hedges against failures in one of the other legs. entitled ‘Global Britain in a competitive age’. The IR was an attempt to avoid the problems of earlier similar The Biden administration’s 2022 NPR reviews, which set out the UK’s military priorities At the time of writing the Biden administration’s without reference to the Treasury’s willingness to NPR has been released to the US Congress but an fund the required spending. The IR was intended to unclassified version has not yet been published. Initial incorporate the work of the Foreign, Commonwealth expectations that the NPR would make significant and Development Office and to be conducted with changes to US nuclear posture were dampened after sufficient Treasury input to ensure that its plans the abrupt removal, two months into its work, of would be fully funded. Deputy Assistant Secretary of Defense for Nuclear and Missile Defense Leonor Tomero, who had initially The most significant change to the UK’s nuclear been in charge of the review.161 A fact sheet released posture in the IR was a reversal of a decades-long by the US Department of Defense confirms that the trend of reductions in the UK nuclear stockpile. The NPR does not follow through with Biden’s campaign planned reduction of the stockpile ceiling to 180 by promise to define US nuclear weapons as having a the mid 2020s164 was said to be no longer possible due sole purpose of deterring a nuclear attack on the US to the ‘evolving security environment, including the or its allies; the phrase used instead is ‘fundamental developing range of technological and doctrinal threats’. purpose’, leaving open the possibility of them serving Instead the stockpile ceiling was increased to 260. other purposes.162 The size of the UK’s nuclear arsenal is said to be Budget documents for FY 2023 show that the Biden determined by ‘maintaining the minimum destructive administration had decided to scrap the sea-launched power needed to guarantee that the UK’s nuclear cruise missile promised in the 2018 NPR. Press deterrent remains credible and effective against the reports confirmed that this decision was mandated full range of state nuclear threats from any direction’ by the forthcoming NPR.163 It appears that neither and ‘the capability required to impose costs on an the W76-2 nor the W93 will be cancelled by the Biden adversary that would far outweigh the benefits they administration. It remains to be seen whether any could hope to achieve should they threaten our, or our policy changes in the NPR will impact upon the design Allies’, security.’165 choices for the W93. Alongside the increase to the overall stockpile, the The UK’s 2021 Integrated Review review reversed the policy of providing information about numbers of operational warheads and the • The IR increased the UK’s stockpile cap to 260 number of deployed warheads and submarines. This warheads and withheld other information about was presented as an extension of a ‘long-standing the UK’s nuclear posture that had previously been policy of deliberate ambiguity’, maintaining that this disclosed. ambiguity ‘complicates the calculations of potential aggressors, reduces the risk of deliberate nuclear • The IR also enlarged the qualification to the UK’s use by those seeking a first-strike advantage, and negative security assurance. contributes to strategic stability.’166 28 Figure 6. Changing threat characterisation and negative security assurances from strategic reviews 2010–2021 2010 2015 2021 No state currently has both the intent Other states continue to have We have previously identified risks and the capability to threaten the nuclear arsenals and there is to the UK from major nuclear armed independence or integrity of the UK. a continuing risk of further states, emerging nuclear states, and proliferation of nuclear weapons. state-sponsored nuclear terrorism. But we cannot dismiss the possibility There is a risk that states might use Those risks have not gone away. that a major direct nuclear threat to their nuclear capability to threaten Some states are now significantly the UK might re-emerge… us, try to constrain our decision increasing and diversifying their making in a crisis or sponsor nuclear nuclear arsenals. They are investing terrorism. Recent changes in the in novel nuclear technologies and international security context developing new ‘warfighting’ nuclear remind us that we cannot relax our systems which they are integrating guard. We cannot rule out further into their military strategies and shifts which would put us, or our doctrines and into their political NATO Allies, under grave threat… rhetoric to seek to coerce others… … the UK will not use or threaten The UK will not use, or threaten to The UK will not use, or threaten to to use nuclear weapons against use, nuclear weapons against any use, nuclear weapons against any non-nuclear weapon states parties Non-Nuclear Weapons State party to non-nuclear weapon state party to to the NPT. In giving this assurance, the Treaty on the Non-Proliferation the Treaty on the Non-Proliferation we emphasise the need for universal of Nuclear Weapons (NPT). This of Nuclear Weapons 1968 (NPT). This adherence to and compliance assurance does not apply to any state assurance does not apply to any state with the NPT, and note that this in material breach of those non- in material breach of those non- assurance would not apply to any proliferation obligations. proliferation obligations. state in material breach of those non- proliferation obligations. We also note that while there is While there is currently no direct However, we reserve the right currently no direct threat to the threat to the UK or its vital interests to review this assurance if the UK or its vital interests from states from states developing weapons of future threat of weapons of mass developing capabilities in other mass destruction, such as chemical destruction, such as chemical and weapons of mass destruction, for and biological capabilities, we biological capabilities, or emerging example chemical and biological, reserve the right to review this technologies that could have a we reserve the right to review assurance if the future threat, comparable impact, makes it this assurance if the future threat, development or proliferation of necessary. development and proliferation of these weapons make it necessary. these weapons make it necessary. 29 Citadel Gate and part of the Waste Management Complex at AWE Aldermaston. The IR says that other nuclear-armed states are extreme circumstance of self-defence, in which the developing new capabilities in order to coerce other very survival of a State would be at stake’.170 Despite a states. The review also enlarged the qualification to statement by the President of the Court that this part the UK’s long-standing negative security assurance of the ruling ‘cannot in any manner be interpreted that it would not use or threaten to use nuclear as having opened the door to the recognition of the weapons against a non-nuclear NPT state that was legality of the threat and use of nuclear weapons’,171 fulfilling its obligations, broadening the reservation nuclear-armed states have incorporated this wording to also cover ‘emerging technologies that could have a into their security doctrines, suggesting that they comparable impact’ to WMDs.167 An assertion from the believe it legitimises their continued possession of wording in previous reviews that ‘there is currently nuclear weapons. no direct threat to the UK or its vital interests’ from states developing WMDs168 has also been removed. The IR confirms that the UK’s nuclear weapons The changing language in the characterisation of continue to be assigned to NATO, as they have been geopolitical risk and the UK’s negative security since the 1962 Nassau agreement,172 but the precise role assurance from the 2010 and 2015 SDSRs to the IR can they play in NATO’s joint nuclear war plan remains be seen in Figure 6. unknown.173 The other element of the UK’s declaratory policy, An assessment of the UK’s nuclear policy under the IR the statement that the UK would only use nuclear and the implications for the Replacement Warhead can weapons in ‘extreme circumstances of self-defence’ be found in the following section. was retained in the IR.169 This language is a reference to the 1996 International Court of Justice’s (ICJ) advisory opinion. The opinion was not able to definitively conclude whether threatening or using nuclear weapons would be legal or illegal ‘in an 30 SiN :tiderC 4. Analysis Janus-faced: nuclear-armed states under This part of the report uses information from the the NPT previous parts of the report to analyse the policy environment that produced the decisions to go ahead with the W93 and the UK Replacement Warhead, the • The NPT-recognised nuclear-weapon states face reasons for those decisions and the inferences that can a fundamental tension between their treaty be drawn about the warheads themselves, based on the obligations and their desire to retain nuclear available evidence. weapons for the foreseeable future. The first sections deal with two key elements of the • Solutions do exist to address the technical issues analysis: the tensions on nuclear-armed states that are underlying this tension through other means than members of the NPT and the factors behind the push producing new warheads. for recapitalising the nuclear enterprises of the UK and US. The following sections deal with policy and the IR, • The significance of the W93 and Replacement its contradictions, the stockpile increase and warhead Warhead Programme is as a statement of numbers. intent, signalling a move away from realising disarmament commitments. The focus then moves to the warheads themselves, looking at the purpose, lineage and characteristics of the W93, before addressing the likely characteristics To understand the decisions to go ahead with the W93 of the UK Replacement Warhead, and the reasons it and the UK Replacement Warhead, it is necessary is likely to be very close in design to the W93. As with to first understand the fundamental tension in the the previous sections, much of the available technical avowed nuclear policies of the five NPT-recognised information relates to the US programme, but has nuclear-weapon states. All are committed both to been leveraged to draw inferences about the UK. the abandonment of their nuclear weapons in the long-term, and to their retention for the foreseeable The level of secrecy surrounding nuclear weapons future. Practical and technical considerations mean in general, and the UK programme in particular, it becomes increasingly difficult to reconcile these means that some of the points made in this part are twin contradictory goals over time. Retaining nuclear necessarily conjectural, based on the best available weapons with a limited service life requires a certain information, rather than confirmed. amount of remanufacture and refurbishment, with some aspects of those processes becoming increasingly difficult as the weapons age and components wear and become obsolete. A notable example of these kind of issues in the US is the loss of the institutional knowledge of how to manufacture a material called Fogbank, which was used in several warhead designs including the W76. Re-establishing the capacity to produce Fogbank cost around $82m174 and delayed the W76-1 programme by around two years.175 The US Government Accountability Office identified similar issues in the production of explosive materials used in around 100 nuclear weapon components. A further example 31 was the Thatcher government’s decision, at the time a weapon system for first time since 1982.178 The W87-1 when a life extension of the Polaris missile was being replacement is planned to have all new manufactured considered, to pay Dupont around £100,000 a month components and a nuclear material manufacturing in order to retain the capability to manufacture a key modernisation plan, requiring large multi-year material. These examples are covered in more detail in investments in component and material capabilities,179 Annexe D. and was recently described as the ‘pathfinder’ programme for ballistic missile upgrades that will This physical infrastructure necessary for develop the infrastructure and technological processes manufacturing components itself requires periodic needed for future programmes.180 maintenance. Externally produced parts will become unavailable without a constant demand driving If the goal of sustaining capabilities within the US production. Changing standards around safety and and UK nuclear weapons programme is considered other factors may require certain components or an absolute necessity, despite the disarmament processes to be changed or replaced. Staff skills that go commitments of the two states, there do not appear unused for long periods of time will tend to atrophy, to be any fundamental technical barriers to fulfilling and staff members themselves may seek alternative that goal through projects such as the JTD, and employment where they can be challenged and break life extension programmes. The same goes for the new ground. It may also be harder to attract new staff. particular requirement cited in the joint Pentagon Consequently, and because it is politically easier to and DOE memo for the W93 programme to sustain fund through new initiatives than as a stand-alone aeroshell capabilities.181 Given the internal preference budget line, the institutional preference within the for sustaining nuclear capabilities through the nuclear enterprises in both the US and UK has been for production of new weapon types, sustaining these these issues to be addressed through the production of capabilities through other means would require new nuclear weapons. substantial political will and determination. Nonetheless, the decision to pursue new warheads The tension between this preference and disarmament should be seen as primarily political decision, rather commitments has doubtless played out within the than a technical one. bureaucracies of these states, with the priorities of the institutions and agencies tasked with sustaining In the UK there was a continuity of policy through nuclear weapon capabilities running counter to the the Blair, Brown, Cameron and May governments of agendas of those who wish to make progress towards reducing the UK’s warhead stockpile as a demonstrable disarmament commitments. In the US, the most act of compliance with disarmament commitments, transparent of the nuclear-armed states, ongoing while at the same time substantially funding the pressure from within the nuclear weapons programme nuclear enterprise, replacing the submarines, missiles for the manufacture of new weapon designs was and warhead, and building up its capacity to sustain its demonstrated by the emergence of the Reliable nuclear weapons system into the future. Replacement Warheads176 and the 3+2 plan.177 The contradictions in this position may not have With these programmes not progressing beyond been politically sustainable in the long term, but the design stage, capabilities within the US nuclear the UK Replacement Warhead and the associated programme have been sustained through life- policy changes in the IR represent a decisive break extension and stockpile stewardship work. This with it. Instead of maintaining capabilities, the UK appears to have been successful. The W76-1 involved is developing a new weapon, increasing its warhead the NNSA undertaking ‘full-scale design activities’ for 32 UK nuclear policy under the Integrated numbers and broadening the circumstances in which Review it would countenance a role for nuclear weapons in its security doctrine. • The warhead cap increase will allow for an These changes are in part presentational. In design increase in the number of deployed nuclear terms, the W93 and UK Replacement Warhead may weapons without any public scrutiny. This could not be any more novel than the previously planned allow an increase of the size of a full nuclear strike IW1 would have been, being based on known and or of the range of strike options, or both. tested warhead designs. Similarly, the UK’s decision on going ahead with a new warhead builds upon • Several of the positions and claims within the IR groundwork laid over 12 years under the NWCSP. appear inconsistent or poorly justified, including However, while the 3+2 warheads would have been the citing of strategic ambiguity as a justification novel designs, they were presented as a consolidation for withholding information about the UK’s of the existing stockpile, enabling further force nuclear posture. reductions, and tied into the life extension plans of existing warheads, replacing them over a 40-year time • Suggestions that the changes in the IR are a period.182 consequence of the desire to assert British power appear to be more credible than the justifications What is most significant about the W93 and the UK provided. Replacement Warhead is the implicit statement of intent. Their presentation as wholesale redesigns • The reversal of transparency measures and signals a move away from realising disarmament reductions in warhead numbers are breaches of commitments under the NPT, resolving the tensions in commitments made under the NPT, as is the IR’s the UK’s previous policy under Blair, Brown, Cameron willingness to countenance an increased role for and May in favour of retrenching and renewing nuclear weapons. its status as a nuclear weapon possessor. In the US the W93 is envisaged as the first in a series of new warheads.183 The IR was originally planned to be released in 2020 but had to be delayed due to the Coronavirus At a time when these two related warheads are pandemic. Although the government has not made the proceeding through the design refinement process, links explicit, it appears that the Replacement Warhead this shift and the accompanying policy will have a Programme and the changes to nuclear policy in determining effect on the concept of operations for the the IR were the product of a single decision-making warheads and on the final chosen designs. Decisions process.185 As such, the changes made in the IR are taken now will have consequences that last for as long an important piece of evidence for the government’s as the two warhead designs remain in service. intentions in beginning the Replacement Warhead programme. The changes to the UK nuclear stockpile, Previous assurances to NPT partners show that the UK to transparency and declaratory posture are also was well aware that upgrading its nuclear capabilities significant in their own right. was a provocative move.184 The consequent damage to the global arms-control regime may be compounded While the changes to the UK’s declaratory posture in by other nuclear-armed states interpreting the move as the IR do not go as far as those in the NPR, parallels providing diplomatic license for them to also develop have been noted by several observers.186 The IR does new nuclear weapon designs. technically preserve the UK’s negative security 33 assurance that nuclear weapons would not be used One definite consequence of ambiguity, particularly against a non-nuclear armed NPT member state in when it is extended to withholding information compliance with their treaty obligations. However, about the UK’s nuclear posture, is that it prevents the threat from chemical or biological weapons, or meaningful public debate about that posture and emerging technologies, that are listed as potentially nuclear policy more generally and blocks democratic warranting a change to that policy, could materialise accountability and scrutiny. In extending this policy quickly. As such, the retention of the assurance of ambiguity to no longer publishing its numbers of provides only a minimal bulwark against an increased deployed nuclear weapons, the UK is also breaching it’s role for nuclear weapons in the UK’s security NPT commitments to transparency about its nuclear policies.187 capabilities.191 This is unacceptable in both diplomatic and democratic terms, and the failure to justify the IR inconsistencies change with substantive argument suggests it is There are a number of apparent inconsistencies motivated more by a desire to escape scrutiny than by and poorly justified claims in the IR’s declaratory strategic calculation. policy. Chemical or biological weapons, despite being inhumane and prohibited under international law,188 Reason for the warhead stockpile increase would not necessarily cause harm on the same scale as A further inconsistency in the IR is the attempt to nuclear weapons. The IR does not attempt to explain justify the increase in the warhead stockpile in terms how their threat or use could meet the threshold of the offensive capabilities and intent of other states: of threatening the survival of a state. Neither is it the ‘developing range of technological and doctrinal explained how emerging technologies, strikes at the threats’. The size of the UK’s nuclear arsenal has long lower end of the ‘full range’ of nuclear threats, or been dictated by an assessment of the scale of damage threats to the security of the UK or its allies could necessary to deter another state. Historically known meet that threshold, despite the IR suggesting that as the ‘Moscow criterion’, the assessment was based any of these factors might result in it abandoning its on the ability to cause damage on a scale deemed negative security assurance. The impression given is unacceptable to the leadership of the then USSR. that the IR is paying lip service to the threshold in the While the precise way this was determined and the 1996 ICJ ruling,189 but is willing to countenance nuclear targets appear to have varied over the years, the basic weapons use in a wider range of scenarios. principle seems to have remained fairly consistent.192 The language in the IR about ‘impos[ing] costs on an Similarly, no explanation is given as to why ambiguity adversary’ confirms that a similar assessment is still and complicating the decision-making of other states central to British nuclear weapons planning. is believed to contribute more towards strategic stability than the alternatives of transparency and The scale of another state’s offensive capabilities has no clarity in order to reduce the possibilities of strategic bearing on the scale of damage from a nuclear strike miscalculation. Ambiguity is said to ‘complicate the that it would deem unacceptable. After publication of calculations of potential aggressors’ and make it less the IR the Secretary of State for Defence, Ben Wallace, likely that an adversary would employ a nuclear first claimed in an interview that Russian defensive strike,190 as they cannot be certain whether this would capabilities were a motivating factor for the increase. engender a nuclear response. No attempt is made An increase in the number of warheads deployed on to explain why this is considered more likely than a each submarine would give greater confidence that hypothetical adversary instead interpreting the lack a nuclear strike could overwhelm missile defence of clarity as a bluff and following through with their systems, but Wallace gave no justification for the planned aggression. omission of this explanation from the IR.193 34 While the new warhead will not come into service for numbers of warheads, with some missiles potentially over a decade, changes in the IR have an immediate carrying a lower-yield variant of the warheads.196 The effect. However, as the cap increase replaced a plan to increase could also be intended to achieve both of reduce the stockpile over a period of around 15 years, these goals, or be primarily intended as a statement the fact it has not been presented as a temporary of intent197 while fulfilling one or several of the above measure suggests it is intended to last beyond the operational objectives. service life of the current warhead. Therefore, we can be relatively certain that the reduction in transparency The statement in the IR that the warhead stockpile and the increase of the warhead stockpile cap were is still set at the ‘minimum, credible’198 level suggests devised with the current nuclear arsenal in mind, but that a substantial increase in the number of targets or are expected to remain in place when the Replacement a desire to target more than one country at a time are Warhead comes into service. Observed activity within unlikely to have played a significant role in the change. the programme194 indicates that warhead numbers A more likely explanation is that decision-makers have already begun to rise. have taken a different view on what is determined to be ‘credible’. This could refer to either increasing The increase in the warhead stockpile will allow the the numbers of warheads used in a full strike or, as number of deployed warheads to increase without was the case with the references to ‘credibility’ in reducing the proportion of the stockpile held in the early years of the UK Trident programme and reserve. The decision to no longer release information the US 2018 NPR, a desire to increase the range of about deployed warheads, missiles and the size strike options. The reference in the IR to remaining of the operational warhead stockpile means that ‘credible and effective against the full range of these increases will not be disclosed to the public state nuclear threats,’199 and ‘doctrinal threats’ may or parliament and could be implemented with no indicate the fielding of missiles carrying a lower- accountability or democratic challenge. yield warhead variant in order to counter the claimed Russian ‘escalate to de-escalate’ strategy,200 but the two Assuming the operational stockpile is set at 60% of possibilities are not mutually exclusive. the total stockpile size, as was the case between 2006 and 2010, the increase to 260 warheads would give an Vanessa Nichols, Director General of the Defence operational stockpile of 156. If these warheads were Nuclear Organisation, confirmed in June 2021 that equally distributed between the three submarines that determinations of ‘credibility’ rely substantially on an are not undergoing deep maintenance, this would result assessment of the perceptions of actors that the UK in a warhead load of 52 warheads per submarine, four wishes to deter, and that decisions of this nature are more than the maximum announced in the 1998 SDR. ultimately taken by the Prime Minister, at that time Boris Johnson. While substantial written assessments There appear to be two broad goals that an increase play a role in decision-making in this area, different could be intended to achieve. A rise in the deployed governments will make different judgements about warhead numbers could increase the overall number ‘how close do they want to be to that line’, and ‘[in] 20, of warheads that would be used in a full strike, in 30 years, where do we pitch our tent?’ Nichols said the order to hold more targets at risk, to target more IR can be seen as the Johnson Government’s statement than one country at the same time, to overwhelm on these questions and that the increase in the stockpile missile defence systems or to offset some decrease in ceiling was driven by a desire to ‘create a little bit more effectiveness of the system.195 Alternatively the rise room’.201 Nichols’ comments appear to be referring could increase the range of different strike options both to decisions around the Replacement Warhead available by fielding missiles carrying different Programme and to the warhead stockpile decision. 35 While the process of devising the IR will doubtless Nukewatch analysis suggests that the stockpile level have involved setting out a number of options returned to its 2010 level around 2017 or 2018, with through detailed and careful analysis in the written substantial increases in warhead numbers in 2019 and assessments Nichols mentions, it should be borne in 2020.205 Despite the uncertainties in estimating warhead mind that this does not mean the final ministerial numbers based on convoy movements, it seems that a decision would have been characterised by careful ramp up of warhead production may have been planned deliberation. The Guardian’s Defence Editor quoted to coincide with the original release date for the IR and sources saying that the warhead stockpile increase the possibility that the stockpile rose above 225 in 2020 was driven by a desire to be more assertive and ‘not cannot be ruled out. In any case, it seems almost certain apologise’ for the UK’s position as a nuclear state.202 that the policy of increasing the stockpile cap presaged Rear Admiral John Gower, a former Assistant Chief an imminent increase in actual warhead numbers. of Defence Staff with responsibilities for nuclear policy, described the decision as being driven by While the practice of submarines patrolling with the ‘nationalist exceptionalism’ characteristic of the missiles carrying a range of warhead loads may have Johnson Government.203 been discontinued by the 2010s,206 the decision to withhold information about the number of warheads Given the contradictions within the IR, these per missile and missiles per submarine, as well as the assessments are more convincing than its own self- number of operationally available warheads, provides justifications. The IR appears to be the product of a scope for it to be recommenced while preventing contested political process. A willingness amongst informed speculation about the exact configuration of some decision-makers to countenance an enlarged role warheads and missiles on the submarines. for nuclear weapons in the UK’s security doctrines and the increase to the warhead stockpile were tempered Production of Mk4A warheads is thought to have by the retention of the negative security assurance begun in 2014 or 2015, with the first units being slated and the reference to the threshold in the ICJ 1996 for loading onto HMS Vengeance, which completed ruling, providing a veneer of legality and adherence to its Long Overhaul Period (Refuelling) refit in February treaty obligations that is inconsistent with the overall 2016.207 Although Nukewatch convoy figures suggest disposition of the review. overall warhead numbers are fast approaching the new cap of 260, it is not possible to be certain. Until Warhead numbers and deployment after the IR recently the Mensa warhead assembly and disassembly Despite the pledge to reduce the stockpile to 180 by facility at AWE was expected to become operational in the mid 2020s in the 2010 and 2015 SDSRs, warhead 2023, and given the programmatic risks of long fallow numbers do not appear to have been decreasing periods where staff and facilities are not engaged in the prior to the policy process that led to the IR. While production process, it seemed likely that a proportion there are uncertainties in estimating the numbers of of the work was intended to be deferred to be warheads, an analysis of nuclear convoy movements completed in Mensa. Given the recent announcement by the Nukewatch network suggests that the warhead of a delay into 2024,208 it remains to be seen whether numbers were reduced by around 12 between 2010 this will now happen and whether production of the and 2015, a trajectory that was consistent with the Mk4A upgrade will be completed by the longstanding planned reductions, before increasing again as the predicted end date for the NWCSP in April 2025. Mk4A programme began production. This is broadly consistent with sources briefing the Federation of The decision to increase the stockpile, coming before American Scientists that warhead numbers did not fall the completion of the Mk4A upgrade, will have set the substantially from the 2010 level of 225.204 baseline size of the Mk4A arsenal for the service life 36 Figure 7. UK warhead stockpile estimates using Nukewatch convoy data 2011–2021209 of the upgraded warhead. Although AWE would retain such a way that prevents the warhead from being the capacity to manufacture more in the future and reassembled’ and that some warheads had been will maintain an ongoing programme of surveillance, ‘modified to render them unusable’211 It would seem maintenance and upkeep, it would be much easier for that these claims were either misleading in terms of the MOD to maintain the arsenal at the level envisaged the numbers of warheads processed in this way or the at the time of initial production than it would have processes used were in fact reversible. been to source additional components from the US to increase numbers if a decision had been taken to Treaty commitments under the NPT increase numbers after the initial production run. As recently as March 2019, the UK’s report to the NPT Preparatory Committee reaffirmed its commitment It seems likely that the recent observed increases in to the goal of reducing its warhead stockpile below the stockpile included warheads assembled using 180, and presented this goal and previous stockpile components from previous stockpile reductions.210 reductions as a ‘step-by-step approach to nuclear This apparent reversal of these reductions calls disarmament consistent with the NPT and… other into question assurances given in 2013 that these treaty commitments’.212 By that measure, the decision reductions were irreversible. In response to an to increase the stockpile cap to 260, reversing the trend FOI request the MOD said that components from of reductions that has been ongoing since the 1990s, is disassembled warheads were ‘processed… in inconsistent with the UK’s disarmament commitments. 37 The consensus documents agreed after the NPT and other non-nuclear attacks, and where a desire to review conferences of 2000 and 2010 committed the be more assertive about the UK’s possession of nuclear nuclear-armed members of that treaty to ‘general and weapons appears to be driving the decision to field complete disarmament’. As part of those agreements a larger nuclear force. The stated desire to remain the UK and the US have committed to a number of ‘credible’ against a range of nuclear threats may steps, including the following: indicate a renewed desire to field warheads capable of • To take further steps to unilaterally reduce their detonating at a lower-yield. nuclear arsenals. W93: purpose, genesis and characteristics • Increased transparency about their nuclear weapons capabilities. • Unilateral initiatives to reduce numbers of non- • The two factors that appear to have played a major strategic nuclear weapons. role in the decision to go ahead with the W93 are • A diminishing role for nuclear weapons in their the desire for a hedge within the sea-launched leg security policies. of the US nuclear triad and a desire to revitalise • That the principle of irreversibility should apply to the nuclear industrial base. nuclear disarmament measures.213 • The longstanding desire for a new warhead The 2010 agreement also recognised that non-nuclear programme combined with a more amenable parties to the treaty had a legitimate interest in policy environment under the 2018 NPR led to the ‘constraining… the development and qualitative W93’s approval. improvement of nuclear weapons and ending the development of advanced new types of nuclear • The limitations of modelling and experimental weapons.’214 development without live testing mean that the W93 will be closely based on tested warhead By reversing the reductions in the UK’s nuclear designs, but may mix elements from several. stockpile, which the UK had presented as steps towards disarmament, instead of further unilateral reductions, by reversing transparency around its This section of the report draws together the available numbers of deployed warheads, and by countenancing evidence about the W93, assessing the reasons given an increased role for nuclear weapons under the IR, for going ahead with the programme, the constraints the UK is in breach of these commitments. If the Mk4A on its design and its likely characteristics. warhead does indeed retain a low-yield capability, and the warheads are again being deployed and produced Rationale in greater numbers under the changes made in the IR, Many of the reasons given for the W93 programme in the UK is also breaching its commitments to reduce the joint Pentagon and DOE memo appear tenuous, or non-strategic weapons. The decision to proceed with simply do not stand up to scrutiny. the Replacement Warhead Programme is directly contrary to the legitimate interest of its treaty partners The W88 stockpile is planned to undergo the Alt 370 recognised in the 2010 agreement. Upgrade between FY 2021 and FY 2026. As the W93 is not expected to enter production until the mid-2030s it More broadly, the IR shows that the Replacement will not be available to supplement the stock of W88s Warhead is being designed in a context where it is during the Alt 370 upgrade as the memo claims.215 considered possible that the UK might decide to use nuclear weapons to respond to chemical, biological 38 While achieving a lighter warhead weight, and The claim in the memo that the W93 is necessary therefore the potential of an increased range with a to limit the risk from delays to the life extension or Trident missile strike and a wider target footprint, is replacement programmes for the W76 and W88 does likely to be a design goal for the W93, this is probably not seem credible. If the DOE has concerns about not a deciding factor in the decision to go ahead with the NNSA’s ability to manage these activities on the programme. The W93 appears to be intended to time and to budget over the two decade period that supplement the two current warhead designs, rather they are scheduled, this would mean that its ability than fully replace them, and it is not clear that it will to deliver its core activities is in doubt. Diverting be lighter than both models. There also does not seem resources, capacity and attention towards an entirely to be a pressing operational need for the benefits that a new warhead design is likely to decrease, rather than lighter warhead would provide. increase, the likelihood of problems arising. If this reason was genuine, the NNSA should have received The memo states the W93 is necessary to support the new management and an amended mission, rather UK’s Replacement Warhead Programme. It says that than the budget for a new warhead programme. the UK programme is particularly dependent on the Mk 7 aeroshell development, and highlights the UK’s While it is not listed as one of the five reasons, role in the joint NATO war plan in order to justify the improvements to adversary defences is listed as one of support that is being rendered. As discussed below,216 the factors influencing the W93 decision. Advances in the replacement UK warhead is certainly dependent Russian and Chinese missile defence capabilities are on the US pursuing a similar programme. The need likely to be factored into the W93 design process, but to wait for US plans was cited in the 2018 Update to are unlikely to be the key reason for approval of the Parliament, and in Summer 2020 the British Defence warhead programme. The recently deployed Russian Secretary took the highly unusual step of lobbying the S-500 system was publicly announced in 2009,218 and US Congress to approve funding for the W93.217 if there had been a specific assessment that it might significantly affect the impact of a US nuclear strike, However, due to this dependency, the UK would not the memo would likely have said so and included this be pursuing a new warhead programme if the US argument in the list of reasons. It is also difficult to were not doing so. Although long-term UK plans know to what extent the design of the warhead itself have been based around the expectation of this will counteract missile defence capabilities. While decision, had the US decided instead to proceed the specific measures used in the Trident system are with a further life extension of the W76, it is a near classified, many of the known methods for beating certainty that the UK would have followed suit. It does missile defence systems, such as decoys and penetration not seem plausible that a desire to support the UK’s aids, are deployed by missiles and do not form part of Replacement Warhead provided the main impetus for the warhead itself.219 It appears the D5LE2 programme the W93 programme, particularly given the cavalier is already planning to incorporate survivability attitude towards UK sensibilities revealed by the US measures,220 so future missile defence improvements unilaterally announcing the Replacement Warhead may have little to no impact on the warhead design. in a congressional hearing. The situation appears to be more a case of the nuclear bureaucracies of both If the US, and by extension the UK, are concerned countries using each others’ warhead plans to justify about the strategic instability caused by missile their own institutional preferences, than of UK needs defence, the most effective remedy would be a driving US decision-making. diplomatic initiative to resurrect the Anti-Ballistic Missile (ABM) Treaty, and bring other nuclear-armed states besides Russia into an updated version of the 39 treaty. The US left the ABM treaty in 2002 in order Although unforeseen problems in complex technical to build a missile defence system, and the novel systems are not unheard of, particularly where there is Russian and Chinese nuclear delivery systems that are a limited circle of knowledge, decisions about whether currently being developed can be traced directly back to mitigate theoretically possible problems should be to this decision. taken on the basis of the full spectrum of costs and benefits. While the hedging strategy of the memo By a process of elimination it would seem the two and the 2018 NPR is justified in terms of the threat factors that have played a significant role in the environment, the philosophy behind the NPR stems decision are the desire for technical hedge within the from a desire for the US nuclear weapons posture to sea leg of the US nuclear triad, in keeping with the include layers of reassurance and redundancy way concept of hedging in the 2018 NPR, and the ambition beyond what was deemed necessary in the past, and to revitalise the US nuclear industrial base. to design a nuclear response for a broader range of scenarios than was previously the case.223 Options exist to address these issues by means other than designing and building a new warhead. W93 antecedents Pursuing interoperability with the Mk5 aeroshell The history of the programmatic antecedents to more vigorously in the IW1 project that became the the W93 support the theory that building up the W87-1221 could have addressed concerns about the US nuclear industrial base was a major factor in ratio of warheads between the W76 and W88, and the decision to go ahead with the new warhead. As also provided a potential hedge against the impact of previously mentioned,224 in Navy budget requests an unforeseen technical issue in the W76. As noted the Mk7/W93 project was previously known as the above,222 there are several potential approaches to Interoperable Warhead,225 This does not mean that the revitalising the industrial base that do not require a W93 warhead is the same as the IW1 warhead would new warhead design. However, this would require have been, but it strongly suggests that it fulfils much enlightened and engaged political leadership willing the same role in the internal bureaucracy of the US to prioritise disarmament treaty commitments to a nuclear enterprise. greater degree than has been the case to date. While the programmatic lineage is less direct in NNSA The desire for a technical hedge within the sea-leg of budget documents, it does appear that the W93 is a the US nuclear triad is a new development following direct outgrowth of the earlier programme. The details the 2018 NPR. The memo claims this is necessary of the transition are covered in Annexe E. Figure 8 because nuclear bombers are less responsive than shows the changes from the US stockpile at the time of ballistic missiles and hedging with ground launched the 2015 Stockpile Stewardship Management Plan to ballistic missiles would increase reliance on a launch- currently funded plans. under-attack posture. This reasoning raises the question of whether these two legs of the triad should The interoperability of the IW1 was being de- be retained at all. Similarly, if additional warhead emphasised from the time the project was re-started. designs are required to guard against the possibility A FY 2019 Feasibility Study,226 which determined that of an unforeseen technical problem in one of the the IW1/W87-1 would not be interoperable with the currently fielded designs, it calls into question the Trident missile, appears to have confirmed a change efficacy of the substantial cost and effort spent by the that was already in motion. It is probable that the US on testing these warheads and qualifying their study did not identify an insurmountable obstacle components through the original production run and to interoperability, but that the policy environment their life extension programme. created by the 2018 NPR’s concept of hedging was 40 Figure 8. US nuclear weapon stockpile plans: Fiscal Year 2015 vs currently funded plans227 41 Handling a warhead during the W76 Life Extension Programme. less amenable to it. The W93 does appear to be a The continuities with the 3+2 plan should be noted. direct outcome of the feasibility study however, being When the W93 comes into service the goal of fielding announced soon after the study’s conclusion with its three different ballistic missile warheads will have design timetable being closely-aligned with what had been achieved within the sea-leg of the US nuclear earlier been proposed for the IW1, and the Navy simply triad. The successor warheads that would have changing the name of the project within their budget. followed the IW1 have also not been abandoned. As The FY 2023 DOE and Navy budgets confirmed that well as the W93, the FY 2022 Stockpile Stewardship the Feasibility Study actually formed the basis for the Plan anticipates a Future Strategic Land-Based ICBM W93/Mk7 Phase 1 Concept Assessment studies.228 warhead to replace the W87, a Future Strategic Sea- Based SLBM warhead to replace the W88, and a Future In summary, the W93 is the consequence of a long- Air-Delivered warhead being delivered in the 2030s. standing desire within the US nuclear programme to A submarine-launched warhead to replace the W76- revitalise its industrial production capacity through 1/2 would follow these, probably in the 2040s. These the design and manufacture of a new warhead and warheads are currently described as ‘notional’,229 but it aeroshell. The desire to adjust the current ratio of is clear that the abandonment of the 3+2 strategy does SLBM warheads (in which there are four times as not mean that there is no longer an ambition within many lower-yield W76 warheads as there are higher the NNSA to develop and produce a range of new yield W88s) and to field a lighter submarine launched warheads over the coming decades, and to shift the warhead may also have played a secondary role. focus of the US nuclear enterprise from sustainment The policy environment of the 2018 NPR provided and life extension to the production of new warhead scope for these objectives to be pursued in a way that models. had not been possible previously. The decision was taken in tandem with the UK decision to develop a Design constraints Replacement Warhead, and both programmes are While the nuclear enterprises in both the UK and being used as internal justification for each other in US have put in place highly sophisticated computer their respective countries. modelling programmes to allow nuclear weapon development in the absence of live nuclear testing, the models do not completely eliminate uncertainty. US modelling is based on Integrated Design Codes 42 .tNaLP xetNaP :tiderC (IDCs), mathematical descriptions of the physical W93 design and characteristics processes involved in nuclear weapons systems.230 The approach of basing a warhead design on The operation of a warhead is broken down into previously tested designs and components, but using separate steps, with the models for each step being them in combinations that have not been tested in refined by experiments,231 such as subcritical tests and full nuclear explosions was planned for the IWs236 and high-energy laser experimentation. IDCs are used to also for the Reliable Replacement Warheads (RRW), reintegrate these separate models and are combined a putative series of new warheads planned under the with the specific data for particular weapon designs Bush administration. The first of these proceeded as to create extremely detailed physical models that are far as selecting a design before having its funding used for the design, maintenance and dismantling of cut by Congress and then cancelled by the Obama weapons.232 Administration in 2008.237 The W93 could be based on one of these previous design, on elements of it, or Predicting the full behaviour of a weapon based on on one of many other fielded or non-fielded warhead its subsystems is an extremely complex endeavour. designs that were detonated during the era of live The models need to account for material damage, nuclear testing. Pentagon briefing at the time the fluid mixing, and the behaviour of high explosives on W93 was approved confirms this will be the approach detonation. A full simulation needs to integrate models taken.238 for ‘material equations of state, material motion, interaction of neutrons with materials, radiation flow’ Systems to increase the surety of the warheads were and more. Experiments used to refine the models a long-term priority for the IWs, with options being can replicate some of the conditions experienced worked up for the planned FY 2020 start date.239 The by warhead components, but not all.233 The FY 2021 focus on surety in the JTD240 indicates that surety NNSA budget says that current models are not technologies developed in that programme will be sufficiently accurate to account for ageing warheads, incorporated into the W93. new threats or new manufacturing techniques, and suffer from limitations in modelling complex physics Another long-standing priority for the NNSA241 is to and integrating multi-scale and multi-dimensional migrate the entire nuclear weapon stockpile to designs models.234 utilising Insensitive High Explosive (IHE), rather than conventional high explosive. IHE is much less sensitive These uncertainties mean that the W93 design is very to physical shocks than conventional explosive, unlikely to radically diverge from warhead designs meaning it is much less likely to explode if the warhead that were tested before the US moratorium on nuclear is damaged in a missile explosion. Its introduction testing came into effect in 1992. While it will be based has been called the ‘single greatest improvement that on live tested weapon designs, it may incorporate can be made to nuclear weapon safety, and part of the stages from different weapons and is likely to involve rationale for selecting a variant of the W87 to replace iterative changes to the designs of its stages. When the W78 warhead was that there is more room within this approach was proposed for the Interoperable the Mk21A aeroshell to accommodate IHE, which Warhead family, it was still considered controversial,235 takes up more space than conventional explosives. as deviating from a known and trusted weapon There are also production efficiencies to be gained design involves inherent uncertainties compared from manufacturing IHE, as safety measures during to replicating a design that has previously been live handling do not need to be as stringent.242 tested. So we can be fairly certain that this approach represents the furthest extent of design innovation planned for the W93. 43 Other technical developments being planned for the The focus in the 2018 NPR on ‘flexibility’ and being W87-1 include replacing a ‘hazardous, inefficient able to meet a range of scenarios with a nuclear and obsolete’ manufacturing process for a ‘strategic response suggests that the W93 design could material’, with a greater potential for recovery incorporate the capability to detonate at different and recycling of the material and allowing it to be yields. produced with cheaper and less hazardous ingredients, and an aspiration to use additive manufacturing of polymers and metals in the manufacturing process.243 It seems likely that these innovations will also be utilised in the W93 programme, particularly given the W87-1’s status as a ‘pathfinder’ programme.244 The focus in the joint Pentagon and DOE memo warhead on building a lighter warhead and countering defensive measures suggest that these factors may play a role in the W93 design. However, it is not clear to what extent missile defence countermeasures will be incorporated into the warhead design, or whether the W93 design will be lighter than both current US SLBM warheads or just the W88.245 While statements from the US administration and the memo suggest no firm decision has been taken about which warheads the W93 will replace in the SLBM stockpile,246 several pieces of evidence suggest that it is primarily intended to replace and/or supplement the W88 rather than the W76. The W93 programme appears to have been temporarily known as the Mk5/ W88 LEP.247 The reasoning in the joint Pentagon and DOE memo around the yield difference between the W88 and W76, and a Pentagon briefing that the W93 is ‘in size’ (i.e. yield) intended to be somewhere in between W76 and W88,248 both imply that the W93 will be tasked with covering targets currently assigned to the W88 in US war plans. As such, while the eventual yield of the W93 may not be as high as the 455kt of the W88, due to increased accuracy,249 it should be expected to be higher than the 100kt of the W76-1. 44 be identical in terms of weight and weight distribution so that the re-entry body behaves identically during flight, regardless of which warhead it is carrying. However, even within this limited scope for divergence, other constraints and pressures mean that meaningful divergence from the design of the W93 is unlikely. The UK will depend on the US not just for the supply of certain warhead components, but also for the process of certification and qualification of those components.250 This process involves rigorous testing in order to provide reassurance that warhead components will behave as intended over the service life of the warhead, and to ascertain the physical limits within which the behaviour of the component can be relied upon. As mentioned above,251 the components in the W93 will be based on components already in use in the US W88 warhead undergoing a drop test as part of the Alt-370 stockpile. While the UK could theoretically decide Life Extension. to develop separate components for its Replacement Warhead, the cost would likely be prohibitively expensive. Much of the equipment and facilities, such UK Replacement Warhead as the centrifuges and vibration table used by the JTD programme are highly specialised and are unlikely • Meaningful divergence from the W93 design is to be available in the UK. Producing alternative parts very unlikely. It would be more expensive and would likely require either a substantial infrastructure probably result in a warhead that was less certain investment or securing the use of US facilities. to work as planned. W93 components that are derived from components in • The warhead will almost certainly follow the existing warheads will come with the added assurance W93 in having a larger yield than the current UK of data from years of stockpile surveillance work on warhead, and it may be designed to also detonate their predecessors. They will also be produced in larger with a lower-yield. numbers than unique UK components would, due to the larger size of the US arsenal and the fact that they will likely be used in multiple warhead designs. Likelihood of diverging from W93 design Producing components at a larger scale not only The design of the UK Replacement Warhead is has implications for the overall cost of each unit, it unlikely to significantly diverge from the design of most likely improves quality control and the overall the W93. Technically speaking, the two warheads only reliability of the components.252 For these reasons the need to be similar in a few key areas. They need to fit UK has routinely purchased US components for use within the same re-entry body, so that will act as a in its warheads, dating back to the late 1950s. This limit to both in terms of size and shape. They will use practice extends to the wholesale incorporation of a common interface with the missile and will need to 45 .yGreNe fO tNeMtraPed SU :tiderC terms. While the UK’s computing capabilities are comparable to those in the US254 and both countries benefit from sharing research data, the drawbacks from deviating substantially from the W93 far outweigh the benefits. The UK could incur substantial additional costs to the Replacement Warhead Programme to produce a warhead that was considered less reliable. The experience of the Chevaline programme illustrates the issues the UK could face, and will doubtless feature in the minds of planners when considering design options for the warhead. As the endeavour to sustain production of the Polaris rocket motor material shows,255 the risks of compatibility divergence last far beyond the design and production stage. Chevaline was the last occasion where the UK pursued a nuclear weapon system with no corollary in the US Model of warheads on top of a Trident C4 missile at the arsenal. The project was subject to cost overruns so National Museum of Nuclear Science and History, New Mexico. substantial it became untenable for it to remain secret. The system was eventually brought into service by the Thatcher government because the project was too far certain systems. Only a handful of UK warheads have advanced for cancellation to save any money, but was not incorporated a US-designed fusing and firing replaced with the Trident system after only 12 years. system, for example.253 In order to maintain the secrecy of its decoy measures, no flight test of the system was ever carried out. The Significant design divergence is even unlikely for the episode remains a salutary lesson for the UK nuclear nuclear material components of the weapon’s physics enterprise of the dangers of diverging from fielded US package, which will not be imported from the US and weapon designs. will be manufactured domestically. The reliance on US components has implications for overall design of the Characteristics weapon, in that the components in the W93 will be Based on the available evidence we can make the designed and certified for use in that weapon design. following predictions. The UK Replacement Warhead The level of certainty that components will function is highly likely to be close in design to the W93. For as desired may drop substantially if the UK’s weapon the reasons above, particularly the experience of the design diverges, particularly for components that need Chevaline system, it is extremely unlikely that the UK to work after the initial detonation of the primary, due will field a different design. As such, the warhead will to the extreme physical conditions within the warhead. probably follow the W93 in having a yield somewhere in between the W76-1 and the W88. The increased The factors above which explain why the W93 will accuracy of the Trident system256 means that the yield be based on existing US weapon designs, and why is unlikely to be as high as the W88, but it would still any changes are likely to be incremental rather than be a significant step up from the yield of the current revolutionary, also mean that the UK Replacement UK warhead. Warhead is very likely to be close to the W93 in design 46 .rkCiLf/SeizNeM Mit :tiderC The government is doubtless aware that many of It is a near certainty that the warhead design will its NPT treaty partners would consider an increase incorporate some of the enhanced surety technologies in its nuclear capabilities to be contrary to its treaty being developed in the JTD, and that the design will commitments.257 However, the disregard for these use Insensitive High Explosives. commitments as displayed in the IR, particularly the decision to increase the warhead stockpile cap, strongly The warhead will be designed to work with the current suggest that the programme will go ahead despite this. life-extended version of the Trident missile, but the planned capabilities of the D5LE2 are almost certain to The emphasis in the IR on being credible against a range be taken into account during the design process. of nuclear threats suggests a lower-yield capability may be designed into the warhead. Part of the initial Work in the JTD on certifying pit-reuse259 suggests that production run could even be adapted to explode with the warhead design could use an identical primary to this lower yield. For the same reason it is likely the an existing US weapon. If so, unless the design uses design process will anticipate that the warhead could the W76 pit, the UK will need to manufacture new pits be hosted on missiles carrying different numbers of according to the chosen design.260 warheads, allowing for a range of strike sizes. The warhead is likely to have a lighter mass than the As with the W93, the warhead will be based on existing current US W88 warhead, but it may not be lighter US warhead designs, but may incorporate different than the W76 and the current UK warhead. elements from multiple designs. Its components will also be based on components in the US arsenal, Measures that increase survivability are likely to be but many will be newly manufactured as updated factored into the design. The warhead components versions. Novel or additive manufacturing is likely will be built so as to be resistant to radiation and to be incorporated in the production process, and in electromagnetic interference, possibly including cold engineering terms many of the major innovations in x-rays. Features intended to defeat future missile the warhead may be in production techniques, rather defence systems are more likely to be built into the than the characteristics of the warhead itself. aeroshell and missile than the warhead itself. The warhead will be housed in the Mk7 re-entry body with its new thermal protection system and release assembly. The Mk7’s new arming, fusing and firing system will probably be one of the outputs of the US Joint Warhead Fuze Sustainment Program.258 If the Biden administration’s Nuclear Posture Review rejects its predecessor’s requirement for multiple warhead designs as a hedge against unforeseen technical problems in the stockpile, the W93 could be designed so that the US can deploy the nuclear explosives package in the aeroshell for a ground- based missile. Whether or not this happens the W93/ Replacement Warhead’s components are likely to be planned for use in future US warhead designs. 47 5. Conclusions and recommendations Conclusions from both states demonstrate the strategic thinking that justified their development and allow us to draw The nuclear-weapon state members of the NPT face a inferences about the likely designs in this report. fundamental tension between their treaty obligations and their desire to retain nuclear weapons for the The decision to proceed with the W93 is a direct foreseeable future. Practical and technical pressures consequence of the 2018 US Nuclear Posture Review, make it increasingly difficult to reconcile these goals which sought to increase the range of nuclear over time. Options do exist to sustain nuclear weapon responses available to planners, to have nuclear production capabilities without taking the provocative weapons fulfil multiple missions and for them act as a step of developing new generations of weapons. States hedge against a wider variety of risks. The UK appears could continue to life-extend existing weapons, or to to have decided to go ahead with its Replacement build updated versions with no increase in capabilities Warhead as part of a decision-making process which if that was not technically feasible. However, to do this also produced the 2021 IR, which increased the size of would require political leadership and a willingness the nuclear stockpile and considers it possible that the to face up to the fundamental incompatibility of new UK might broaden the situations in which it would use nuclear weapons with disarmament commitments. nuclear weapons. In the US the W93 programme is the consequence of The increase in the UK’s nuclear stockpile size allows a longstanding desire for a new warhead programme for a greater number of nuclear weapons to be to sustain capabilities within that country’s nuclear deployed. This means more warheads could be used enterprise, combined with the more receptive in a full nuclear strike, planners could have a greater policy environment for such a venture under the variety of strike options, or both. These changes Trump administration. Although the W93 and UK would be made without any public or parliamentary Replacement Warhead may not be significantly discussion or oversight. The decision to withhold different in design terms from previously planned previously released information about the number of US warheads, such as the IW1, the presentation of deployed nuclear weapons and the numbers carried them as new is significant as a statement of intent. on each submarine and missile is justified in terms In the US the W93 is envisaged as the first in a series of ‘strategic ambiguity’, but this claim is not well of new nuclear warheads. In the UK the Replacement substantiated. Suggestions that the stockpile cap Warhead’s probable increased capabilities, and the increase has more to do with a desire to assert British IR’s increase in the warhead stockpile mark a decisive power than an objective assessment of risk are more break from the policy under the Blair, Brown, Cameron persuasive than the reasons given in the IR. and May governments to retain existing capabilities while reducing warhead numbers. The language of ‘credibility’ used in the IR, and echoed in the 2018 US NPR, suggests that the concerns which Although both the W93 and UK Replacement Warhead were used to justify the lower-yield capability in are yet to reach the stage of selecting a final design, the UK’s Trident warhead are once again ascendant key decisions are happening now. Design decisions in nuclear planning circles in the US and UK. This taken today will have consequences that will last capability, which probably took the form of a variant for the service life of these weapons and may have of the warhead with a dud secondary, was publicly implications for the UK’s nuclear posture throughout acknowledged on multiple occasions when the current that time. While there is no public information about warhead first came into service. During this time the design options being considered, policy documents British submarines probably went to sea fielding missiles with different strike options, including some 48 with warheads configured for a lower-yield strike. This in constraining the development of new and improved practice may have been discontinued by the 2010s, nuclear weapons, and together these changes are likely but the stated desire in the IR for the UK to remain to further weaken a treaty regime which is already ‘credible’ against a range of nuclear threats and the struggling with a loss of credibility and accusations of changes to warhead numbers may indicate that it has bad faith on the part of nuclear weapon states. been reintroduced, or a desire to retain the option to do so in the future. This is a clear demonstration of the limitations of a model of disarmament whereby nuclear-armed The limitations of the experimental and modelling states make incremental reductions in their arsenals techniques used to develop nuclear weapons without at a pace determined by their political convenience. live testing mean that the W93 is unlikely to radically Instead of reorganising the UK nuclear enterprise depart from previous US weapon designs that with the aim of delivering on the UK’s disarmament have been live tested. However, it may be based on commitments, the Blair, Brown, Cameron and May elements from several previous weapons. The original governments carried out warhead stockpile reductions justification for the W93 suggest it will be designed alongside a renewal of the physical infrastructure with a yield that is able to destroy targets allotted to of the programme. Even if it was not intended by W88 warheads in current US strike plans. While the policymakers at the time, this approach laid the increased accuracy of the Trident system probably groundwork for the current government to begin means this can be accomplished with a lower yield building a new nuclear warhead that may well field than the 455kt W88, it is likely to have a higher yield an increased yield, whist increasing the size of its than the 100kt W76. It may also incorporate a lower warhead stockpile. Internationally, non-nuclear yield-capability. states that have historically supported a ‘progressive’ incremental approach to nuclear disarmament261 The technological dependency of the UK nuclear should consider the shortcomings of this approach, as weapons programme on the US means the UK revealed by this turn of events. Replacement Warhead is likely to have a similar design to the W93, and may therefore produce a significantly The need for negotiated disarmament agreements to higher yield than the current UK warhead. Doing reduce international tensions is greater than at any otherwise would expose the Replacement Warhead time since the end of the Cold War. The nuclear threats Programme to additional costs and programmatic issued in relation to the Russian invasion of Ukraine risk throughout the life of the warhead, resulting in are a stark illustration of the instability and mutual a design that was more expensive but less certain insecurity that characterises a nuclear-armed world, to function as intended. A lower-yield capability is a the political obstacles to progress in disarmament and strong possibility if one is designed into the W93. the unthinkable alternative if progress is not made. Whatever the outcome of that conflict, still ongoing at The UK IR’s reversal of stockpile reductions, reductions the time of writing, the nuclear-armed states will still in transparency and its countenancing of an increased need to find the political will to advance towards their role for nuclear weapons in security doctrine are all shared objective of a world without nuclear weapons. breaches of commitments made within the NPT. The That goal is as relevant and urgent as it ever has been, reversal of cuts to the UK’s warhead stockpile call into and the January 2022 joint statement from the five question public assurances that components from NPT-recognised nuclear-weapon states,262 while falling dismantled warheads were being rendered unusable. far short of their Article 6 commitments, shows that The Replacement Warhead project runs contrary to common ground could still be found on this issue at a the recognised interest of non-nuclear NPT members time of rising tensions. 49 In the UK, where the government’s nuclear policy has There are further reasons that the UK Replacement been described by a former insider as being driven Warhead Programme should be subject to greater by ‘nationalist exceptionalism’, the political will to scrutiny. While no official estimate of the budget for make progress on disarmament is unlikely to emerge the programme has been published, the current US without external scrutiny and pressure. In the first estimate for the W93 is between $13.4bn and $15.5bn, instance that scrutiny and pressure should aim to equivalent to between £10.6bn and £12.3bn. Even in the ensure that nuclear weapon upgrades such as the US context this is a provisional figure and the budget Replacement Warhead Programme do the minimum may be revised upwards. In order to ensure that possible harm to the international arms control public money is as well spent as possible, there should regime. While the relative size of the UK’s nuclear be considerably more scrutiny of the Replacement forces means it is unlikely to play a significant role in Warhead Programme and the government’s nuclear a renewed nuclear arms race, a reversal of reductions weapon upgrades more generally. The annual reports from the NPT nuclear-weapon state that had reduced carried out by the Defence Select Committee while the its stockpile to the lowest level will still damage the Trident system was being built provide a good model credibility of the treaty. Fielding a new warhead with for this. an increased yield would doubtless have a similar effect. As the Replacement Warhead Programme is at an early stage in development, the potential harms to However, the way the UK nuclear enterprise currently the international arms control regime can be avoided operates provides little scope for oversight, scrutiny with sufficient political will and leadership. The most or democratic accountability. The move away from appropriate course of action would be for the UK to transparency in the IR is a retrograde step that limits forgo a new warhead design and instead transition to the scope of public discussion and debate about the extending the life of the current warhead until such merits of the UK’s nuclear posture at a critical time. time as the UK is ready to disarm. If this does not While preparation for the Replacement Warhead happen, for example if there are technical reasons decision had clearly been taking place at the time which make this untenable, the Replacement Warhead of the 2019 election, no public disclosure was made Programme should involve no increase in the offensive during the campaign that it was imminent. capabilities of the warhead. Aside from the safety and surety measures that appear to be currently This aversion to accountability echoes the December planned for the warhead, the UK should draw upon 2006 White Paper on replacing the UK’s submarine its longstanding disarmament verification work265 to fleet, which was published less than seven months ensure that the new warhead can easily be disarmed after an election where the government downplayed and dismantled, with a team of international observers its importance as an election issue and did not from non-nuclear states able to verify that its disclose that there were any concrete plans in place.263 components have been put permanently beyond use. However, the Dreadnought submarine programme It should also be designed for indefinite life extension, was then subject to a parliamentary vote. The warhead in order to eliminate any future technical pressures to programme was not, despite a public undertaking by develop subsequent warheads. These objectives should the then Foreign Secretary in 2007 that it would be.264 be clearly communicated to the public and the UK’s The substantial government majority in parliament NPT treaty partners. after the 2019 election confirms that this decision was not taken through any uncertainty about the result, The UK dependency on the US nuclear weapons but from a decision not to consult parliament on programme means it would not be able to deliver a principle warhead that fitted these criteria on its own. The UK’s 50 warhead plans were so reliant on the US that they 2. The UK government should release a detailed appear to have been put on hold until a decision was justification for the recent increase to it’s warhead taken to go ahead with the W93. The risks of fielding stockpile cap, in order to allow public debate about a separate weapons platform are so substantial that the merits of the change. the UK’s nuclear weapons programme as currently constituted is bound to follow the US programme. 3. This justification should include a statement about the status of any lower-yield capability on the UK’s In order to deliver a warhead programme that is more current warhead and a timetable for the permanent commensurate with its disarmament commitments, phase-out of this capability, in keeping with its the UK would need to use both its diplomatic influence commitments to the 2000 and 2010 NPT Review and its input into the W93 programme to lobby for Conferences. both warheads to be designed such that they didn’t involve an increase to the UK’s nuclear capabilities. 4. The UK should abandon its doctrine of strategic Although the chances of this course of action proving ambiguity. It has the potential to confuse decision- successful may be considered slight, this does not making in a crisis and any strategic benefit it absolve the UK of its disarmament obligations. might provide is outweighed by the harms done to democratic scrutiny, accountability and strategic Recommendations stability. Nuclear Information Service advocates for the swift 5. The UK government should immediately make realisation of the UK’s disarmament commitments in public the size of its operational warhead stockpile, order to achieve the UK government’s professed goal as well as the maximum number of missiles and of a world without nuclear weapons. The decision to warheads carried on each submarine. It should go ahead with the Replacement Warhead Programme commit to updating parliament on any changes to runs contrary to this goal and to the interests of these numbers. non-nuclear states. If the programme goes ahead as planned despite this, the following steps are suggested 6. The UK’s nuclear weapons programme, particularly to help mitigate the harm. the Dreadnought programme and the Replacement Warhead Programme, should be subject to detailed 1. the Government should make a public statement parliamentary scrutiny to ensure the best possible to the effect that the programme will not result in management of the public funds being spent. A any change to the UK’s nuclear capabilities, and central element of this scrutiny should be annual any changes to the warhead design will be solely inquiries and reports by the Defence Select focussed on: Committee, as was the case during construction a) Improvements to safety and surety of the first generation of Trident submarines and b) Ease of verifiable dismantlement, using lessons warheads. learned in the UK’s disarmament verification research c) Easy replacement and life-extension of components, in order to eliminate any technical pressures for new future warhead designs while the UK remains a nuclear weapons state. 51 Annexes Annexe A. Planned outputs from the W93 Since 2016 the two countries have been working and Mk7 programmes Fiscal Years 2021– together on the JTD project. The stated purpose of the 2022 JTD is to develop demonstration warhead systems that are not tied to a particular warhead design but A key output of the first phase of the Concept could potentially be deployed in a number of future Assessment and Refinement Stage is the Phase 1 study warheads. Reference warhead designs are used so that report, which was produced in FY 2021, and included multiple elements of the design can be assessed from a recommendations for Phase 2, the Feasibility Study ‘system-level perspective’ rather than in isolation.273 and Design Options phase.266 When the JTD was announced the UK MOD implied Work to be done before the transition to Phase 2 that the project’s outputs could be used in a future included documenting the results of the Concept warhead, and said that, as well as working to increase Assessment Study, assessing whether the technologies safety and security, the project was investigating envisaged in different designs are mature enough to be advanced manufacturing technologies.274 The areas included,267 and considering how to mitigate potential of focus are: ‘nuclear weapon science, component vulnerabilities.268 and subsystem technologies, cost and time-efficient production methods, and systems integration.’ Work in FY 2020 included defining a working group Compared to other US stockpile development work, charter and drafting a programme plan and cross- the focus of the JTD is relatively short-term,275 so it can agency plans,269 and FY 2021 plans include producing be assumed that many of the technologies it develops an integrated master plan and master schedule for will be utilised in the W93 and UK Replacement both the W93 and Mk7. Cross-agency coordination Warhead. appears to be an ongoing focus of the programme.270 The choice of technologies in the JTD is a balance According to Navy budget requests, documents to be between integrating those that are already deemed produced for the Mk7/W93 programme in FY 2021 sufficiently mature and developing others based on included a systems engineering plan, a stockpile the expected requirements of future warhead designs. concept of operations, and a preliminary reliability and The project works with full system architectures, safety assessment.271 subsystems and components, integrating them into the reference system design276 and developing FY 2022 plans include initial data analysis for fire through the stages of manufacture, ground testing and control software support for the W93 and the early assembly until they are deemed ‘flight ready’.277 stages of developing material for the aeroshell, including ground testing.272 One purpose of the JTD is sustaining and developing capabilities278 and developing the expertise of people Annexe B. Joint Technology Demonstrator working in both countries’ programmes. The project and other UK-US cooperation also hopes to reduce the risks involved in producing and certifying components so they can be integrated UK-US cooperation on warhead design has been into fully-fledged weapon designs as easily as ongoing since the two countries signed the 1958 MDA. possible.279 However, their active cooperation on this generation of warheads pre-dates the announcement of the W93 and The JTD is comprised of 3 workstreams. Workstream UK Replacement Warhead Programmes. 1 involves the NNSA, US Navy and MOD, focussed on a reference design using the Mk5 aeroshell, which 52 currently houses the W88 warhead. Workstream 2 as ‘system agnostic’ and is intended to change over involves the NNSA and US Air Force and focusses on the course of the project to retain its relevance to all the Mk21 aeroshell, which currently houses the W87 future systems.291 The change presumably reflects the warhead. Workstream 3 is a collaboration between the decision to go ahead with the W93, and the current MOD and NNSA and works on technology maturation reference system is likely to be based on the expected in general.280 Although the documentation around characteristics of the Mk7 Aeroshell. the JTD stresses that the aeroshells chosen for each workstream are reference designs, it is notable that the The scope of the JTD goes beyond joint experiments. two designs are those that the IW1 would have been The JTD has also seen DOE contractors being carried in. integrated into UK nuclear weapons work during FYs 2019 and 2020.292 The two countries also have an Several hydrodynamics tests have been carried out integrated computer network system called JODE, for under the JTD. FY 2017 saw two relating to certification direct data exchange and communications between exercises for pit reuse and the use of insensitive the weapons programmes of the two nations.293 JODE high explosive (IHE) for primary detonation in the may be linked to the Kansas City National Security future. Another in FY 2019 related to certification and Campus (KCNSC) hybrid cloud platform, a secure qualification work.281 Others were carried out in FYs enterprise network enabling the sharing of classified 2018, 2020, and 2021.282 data, secure communications and hosting specialist classified applications to ‘allow design, development Other work has included a ‘hubcap experiment’ in and prototyping of weapon hardware, software, FY 2017, which examined the fracturing of advanced systems, and applications’.294 This platform was manufactured components under explosive stress283 planned to be used for the JTD in FY 2021,295 and the In FY 2018 Two Ground Test Units were also tested involvement of KCNSC suggests that this part of the at the Little Mountain test facility,284 which tests programme focusses on non-nuclear hardware. components’ resilience against physical shocks and vibration as well as radiation and electromagnetic The FY 2020 Budget envisaged future milestones for interference.285 The tests used hardware created the JTD between FYs 2021 and 2024. Workstream 1 under the enhanced surety programme,286 but were was to complete ground testing of the Mk5 design, also listed under the heading of weapons technology carry out two hydrodynamic experiments, a ‘tri-lab development in the FY 2021 budget, suggesting a photon radiography experiment’ and US/UK systems broader application.287 demonstrations and studies’. However, the move away from the Mk5 reference design may have changed In FY 2017 the JTD completed its planning phase and priorities. Over the same time period Workstream moved into the execution phase, which consisted 2 was to ‘conduct system mechanical and electrical of validating a reference system design and ground ground testing demonstrations’ of the Mk21.296 testing.288 during that year JTD surety work also resulted in prototype hardware being produced.289 Outside the scope of the JTD the US and UK also investigated ‘non-nuclear survivability options and In FY 2020 Workstream 2 completed its final round capabilities’297 and worked on fissile material air of testing with a flight simulation using centrifuges transport containers in FY 2017.298 In FYs 2020 and and vibration equipment,290 and JTD Workstream 2021 the two nations were working on ways to assess 1 transitioned away from using a Mk5 reference system survivability ‘under a non-ideal blast’. The system. The workstream is currently using a different research seems to have involved testing the cold x-ray ballistic missile design, but is officially described response of materials at the National Ignition Facility 53 (the US high-energy laser facility) using both three- The immediate focus of the programme is on dimensional and two-dimensional test objects.299 The developing technologies that will need to be UK is also listed as a partner in a programme of work included regardless of the final missile architecture: which began in FY 2021 trying to address digital risks a post-boost control system, guidance instruments, to the US nuclear enterprise.300 radiation-hardened electronics, battery technologies and cyber-security frameworks.306 The timescale of Annexe C. Trident D5 Life Extension 2 the project will be similar to the D5LE which began concept studies in the late 1990s, began design in 2004, It was originally intended that, after completion of the completed design in 2011 and was deployed in 2017.307 A initial D5LE life extension to the Trident D5 missile system requirements review for the D5LE2 is expected which extended its service life until the end of the in FY 2025, followed by ground testing and a first test 2030s,301 the US would develop a replacement missile. flight in FY 2032, followed by early production. The However, a decision has since been taken to instead missiles will be loaded onto submarines in FY 2039.308 put the missile through a second, more extensive, life Annexe D. Known problems in the US and extension programme. UK nuclear enterprises caused by lost production capabilities The D5 Life Extension 2 (D5LE2) programme will extend the life of the missile into the 2080s. The programme is justified in terms of the obsolescence of ‘safety critical’ One notable example of a problem caused by a lost components, including flight electronics and critical capability in the US nuclear weapons programme, components, that pass out of their qualification period is the loss of the institutional knowledge of how to by FY 2039, and are no longer supported or produced manufacture a material called Fogbank. Fogbank by the industry. Stocks of other components are is thought to be an aerogel that channels radiation expected to be used up in flight tests or for spares. between the primary and secondary stages, and was used in several warhead designs including the W76.309 While the first Trident missile life extension (known Few records were kept at the time of manufacture in as D5LE) just extended the life of some missile the 1980s, and production was dormant for 25 years, components, the D5LE2 will be more substantial, during which time almost all staff with expertise involving shipboard systems too. The approach retired or left.310 Re-establishing the capacity to will be a mix of incorporating some cost-effective produce Fogbank cost around $82m311 and delayed the replacement technology, such as solid rocket motors W76-1 programme by around two years.312 and igniters, and redesigning other systems, such as the avionics, guidance and the system architecture.302 A 2019 US Government Accountability Office (GAO) report identified similar challenges to Fogbank in It will use some components that are still in the production of specialised explosive materials production, but will restart the industrial base for needed for around 100 different nuclear weapon other components. The programme intends to increase components. These were created decades ago and the the capabilities of the missile, although cost is also said knowledge base is gone. Some have a very limited to be a key driver.303 Budget documents say the D5LE2 supply, including one that has only one container left. will deliver the ‘range and accuracy’ of the current Even if the ‘lost recipes’ can be recovered, suppliers system, but will also address the improved defensive would need to be found for small quantities of capabilities of ‘near peer adversaries’304 and will need specialist materials that meet the relevant standards.313 ‘additional attributes’ to make it more survivable.305 Additionally, a 2021 GAO report identified similar challenges to Fogbank in producing high quality 54 depleted uranium (DU) and components using a planned. Two further interoperable warheads were DU-niobium alloy.314 The second Trident missile life also still planned although they were now known as extension programme is being justified on similar the BM-Y and BM-Z respectively.322 grounds.315 According to the NNSA FY 2021 budget, the study to An example from the UK programme occurred when investigate the interoperability of the now W87-1 was the Thatcher government was considering extending completed in FY 2019323 The same budget, five months the life of its Polaris missiles so that Chevaline could after the end of FY 2019, included the initial request remain in service. They encountered significant for the W93 and Mk7. The start date for the W93 was problems trying to acquire fibreglass material that closer to that proposed for the IW1, despite it more would have been needed for the casing of the first closely resembling the BM-Y and being much closer to stage rocket motor. No equivalent could be obtained that warhead in its production cycle.324 The implication on the open market, and numerous live firing tests of this is that the W93 project is filling an internal would have been needed for certification if one demand for warhead design activities to be carried out were available. While the life-extension option in this time period. was being considered, the UK paid Dupont around £100,000 a month to retain key personnel and keep The interoperability of the IW1/W87-1 was being de- the production plant certified, so that the capacity emphasised from the time the project was re-started. to manufacture additional batches of the material The 2019 feasibility study formalised a move away remained available.316 from interoperability that was already in effect, and therefore may have been driven by factors beyond Annexe E. From the Integrated Warhead to warhead design considerations. Although the IW1 the W93 project was accelerated in FY 2013 and therefore may not have spent as long as possible considering the Work on IW1 had been planned to re-start in FY potential vulnerabilities of its chosen design, it is 2020,317 but funds to re-start Phase 6.2 of the project, striking that the project got to the stage of identifying the feasibility study and design options phase, were a pit design without there being any question over its requested in the FY 2019 budget.318 This work was to potential interoperability, despite that being the major include a system requirements definition, early design overall strategic focus of the NNSA. It seems unlikely work, and planning for the programme, including that an insurmountable obstacle was then discovered flight and ground tests.319 It was intended that the in the 2019 feasibility study. A more probable scenario warhead would come into service by 2030 to replace is that the policy environment created by the 2018 the W78, but the earlier intention that it could also NPR’s concept of hedging meant that there was no replace the W88320 was no longer certain, and part political appetite for overcoming technical obstacles in of the work plan in FY 2019 was to investigate the pursuit of interoperability. feasibility of deploying the NEP of the warhead on a Trident missile.321 While a replacement for the W78 seems to have been considered the highest priority due to age and service Seven months later, in October 2018, the project had life considerations, and the W87-1 does serve as a been renamed the W78 Replacement Warhead and justification for some reinvestment in the US nuclear was to use the Mk21 re-entry vehicle used in the W87, industrial base, such as the targets for pit production, but the study to use it on a Trident missile was still it apparently does not offer the same benefits as a new warhead project would. The rebuilding of 55 the industrial base for building re-entry bodies as mentioned in the DOD-DOE memo, would appear to be a prime example. As a consequence, a little over a year after the FY 2019 feasibility study completed, the W93 was announced with a design period closely fitting what had previously been planned for the IW1, and it inherited the Navy programme that was previously slated for that warhead. The FY 2023 DOE and Navy budgets confirmed that the relationship was so direct that the Feasibility Study actually formed the basis for the W93/Mk7 Phase 1 Concept Assessment studies.325 Navy plans for FY2023 include investment relevant to both aeroshell development and recapitalisation of the industrial base.326 56 Endnotes 1. GOV.UK. ‘Defence Secretary Announces Programme 8. US budget documents suggest that conversion of the to Replace the UK’s Nuclear Warhead’, 25 February Trident missile stockpile is ongoing and may last until 2020. https://www.gov.uk/government/news/defence- the D5LE2 programme begins in 2023 (see ‘Fiscal Year secretary-announces-programme-to-replace-the-uks- (FY) 2022 Budget Estimates – Justification Book Volume nuclear-warhead. 1 of 1 – Weapons Procurement, Navy’. Department of 2. Dan Leone. ‘Planned W93 Warhead Will Contribute Defense, May 2021. https://www.secnav.navy.mil/fmc/ to New U.K. Nuke, DOD Officials Say’. Defense Daily, fmb/Documents/22pres/WPN_Book.pdf. p2,4). Media 13 February 2020. https://www.defensedaily.com/ reports that the September 2017 visit of HMS Vigilant planned-w93-warhead-will-contribute-new-u-k- to the Kings Bay submarine base in Georgia, which nuke-dod-officials-say/nuclear-modernization/;Jamie attracted media attention due to the behaviour of the Doward. ‘Pentagon Reveals Deal with Britain to Replace crew, was to pick up nuclear warheads are likely a Trident’. The Observer, 22 February 2020, https://www. misunderstanding of the real purpose of the trip, which theguardian.com/uk-news/2020/feb/22/pentagon-gaffe- was probably to swap the submarine’s load of missiles reveals-uk-deal-replace-trident-nuclear-weapon. with life-extended versions. 3. Charles A Richard. ‘Statement of Charles A. Richard, 9. See Peter Burt. ‘AWE: Britain’s Nuclear Weapons Commander United States Strategic Command, before Factory; Past, Present, and Possibilities for the Future’. the Senate Committee on Armed Services’, 13 February Nuclear Information Service, 2016. https://www. 2020. https://www.armed-services.senate.gov/imo/ nuclearinfo.org/wp-content/uploads/2022/04/NIS_AWE_ media/doc/Richard_02-13-20.pdf. p13. Executive_Summary.pdf. p26–27. and ‘Warhead Convoy 4. See Matthew Taylor. ‘Britain Plans to Spend £3bn on Movements Summary 2016’. Nukewatch, 2016. http:// New Nuclear Warheads’. The Guardian, 24 July 2008, www.nukewatch.org.uk/wp-content/uploads/2014/04/ sec. Science. https://www.theguardian.com/world/2008/ Convoy-log-2016.pdf. jul/25/nuclear.weaponstechnology. Building new 10. See Hans M. Kristensen and Matt Korda. ‘World infrastructure, often regarded as the fourth element in Nuclear Forces’. In SIPRI Yearbook 2021: Armaments, the system, is an intrinsic part of the upgrade projects. Disarmament and International Security. Oxford 5. ‘The United Kingdom’s Future Nuclear Deterrent: University Press, 2021. https://www.sipri.org/sites/ The Submarine Initial Gate Parliamentary Report’. default/files/2021-06/yb21_10_wnf_210613.pdf. p333–404. Ministry of Defence, May 2011. https://assets.publishing. 11. Federation Of American Scientists. ‘Status of World service.gov.uk/government/uploads/system/uploads/ Nuclear Forces’. Accessed 9 November 2021. https:// attachment_data/file/27399/submarine_initial_gate.pdf. fas.org/issues/nuclear-weapons/status-world-nuclear- p4. forces/. 6. Comptroller and Auditor General. The Defence Nuclear 12. Sanem Topal. ‘Nuclear Weapon Modernisation: Attitudes Enterprise: A Landscape Review. London: National of Non-Nuclear Weapon States’. Nuclear Information Audit Office, 2018. https://www.nao.org.uk/wp-content/ Service, August 2021. https://www.nuclearinfo.org/wp- uploads/2018/05/The-Defence-Nuclear-Enterprise-a- content/uploads/2021/08/Attitudes-to-Nuclear-Weapons- landscape-review.pdf. p46. Modernisation.pdf. 7. Lockheed Martin. ‘Modernized Lockheed Martin Trident 13. See Claire Mills. ‘UK-US Mutual Defence Agreement’. II D5 Missile Test Certifies Submarine for Patrol’, 28 Standard Note SN/IA/3147. House of Commons, 20 March 2018. https://news.lockheedmartin.com/2018-03- October 2014. https://researchbriefings.files.parliament. 28-Modernized-Lockheed-Martin-Trident-II-D5-Missile- uk/documents/SN03147/SN03147.pdf. Test-Certifies-Submarine-for-Patrol. 57 14. DST Secretariat Strategy Secretariat. ‘Copy of the Trident 25. See ‘The Decision to End U.S. Nuclear Testing’. Arms Holbrook Warhead Programme Project Definition Control Association. Accessed 31 December 2021. https:// Document or Equivalent’, 13 October 2015. https:// www.armscontrol.org/act/2019-12/features/decision-end- assets.publishing.service.gov.uk/government/uploads/ us-nuclear-testing. system/uploads/attachment_data/file/470321/20151013- 26. Reprinted by permission from Nature. Taken from FOI_2015_07375.pdf. ‘Science of nuclear warheads’, O’Nions et al. © 2002. 15. Peter Burt. ‘AWE’. p10. 415, pages 853–857 (2002). The figure is presented in 16. Ibid. p25. reference to understanding the performance of an 17. Nicola Butler and Mark Bromley. ‘Secrecy and existing weapon stockpile, but the process for new Dependence: The UK Trident System in the 21st Century’. warhead development is the same. BASIC: British American Security Information Council, 27. Mark Welland. ‘Hydrodynamics – Cooperation with November 2001. p16 France’, 7 July 2010. D/CSA/13/1/2 (359/10). http:// 18. See Suzanne Doyle. ‘The United States Sale of Trident to nuclearinfo.org/sites/default/files/04%20Mark%20 Britain, 1977–1982: Deal Making in the Anglo-American Welland%20Hydrodynamics%20paper%20070710.pdf Nuclear Relationship’. Diplomacy & Statecraft 28, no. 3 (3 28. See ‘Anglo-French Nuclear Co-Operation and the July 2017): 477–93. https://doi.org/10.1080/09592296.2017. “Teutates” Programme’. Nuclear Information Service, 1347447. The 1980 agreement was for purchase of the C4 November 2010. https://www.nuclearinfo.org/ Trident missile, but sale of the newer D5 Trident missile wp-content/uploads/2020/09/NIS-Anglo-French-co- was later agreed by the Reagan administration. operation-briefing-November-2010-1.pdf. 19. Michael Clarke. ‘Does My Bomb Look Big in This? 29. Nuclear Information Service. ‘UK and France Extend Britain’s Nuclear Choices after Trident’. International Warhead Research Collaboration into New Areas’, 5 Affairs 80, no. 1 (January 2004). p55. 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Q358. 83. ‘Fiscal Year 2016 Stockpile Stewardship and Management 68. HM Stationery Office. ‘The Future of the United Plan’. National Nuclear Security Administration (NNSA), Kingdom’s Nuclear Deterrent’. p23. March 2015. https://www.energy.gov/sites/default/ 69. See Michael Quinlan, ‘The British Experience’ in files/2017/08/f36/FY16SSMP_FINAL%25203_16_2015_ Henry D. Sokolski, ed. Getting MAD: Nuclear Mutual reducedsize%5B1%5D.pdf. ch2 p25–26. Assured Destruction, Its Origins and Practice. Carlisle/ 84. See the ‘W83 Antecedents’ section on page 40 and Pa: Strategic Studies Institute, 2004. p272. Quinlan uses Annexe E. the formulation ‘[t]his has been conjectured to mean 85. Adapted from Fiscal Year 2015 Stockpile Stewardship and that some missiles might have only a single warhead, Management Plan. See note 74. and that warhead might have reduced explosive yield’ 86. Aaron Mehta. ‘Inside America’s Newly Revealed Nuclear when he was doubtless in a position to know for Ballistic Missile Warhead of the Future’. Defense News, certain. Presumably this form of words allowed him to 24 February 2020. https://www.defensenews.com/smr/ confirm conjecture that is in the public domain without nuclear-arsenal/2020/02/24/inside-americas-newly- breaching the Official Secrets Act. revealed-nuclear-ballistic-missile-warhead-of-the-future/. 70. Hansard. ‘Trident’. 87. Department of Energy. ‘FY 2022 Congressional Budget 71. Geoffrey Chapman. ‘‘Sub-Strategic’ Trident’. In Request’. p74. Workshop on UK Nuclear Weapons Politics, Student 88. ‘FY 2021 Congressional Budget Request – National and Young Pugwash Conference. University of Leicester, Nuclear Security Administration – Federal Salaries 2022. https://youtube.com/V1UvjYN6K0k. and Expenses, Volume 1: Weapons Activities, Defense 72. ‘Nuclear Weapons’. Hansard UIN 170597, 17 March 2021. Nuclear Nonproliferation, Naval Reactors.’. Department https://questions-statements.parliament.uk/written- of Energy, February 2020. https://www.energy.gov/sites/ questions/detail/2021-03-17/170597. prod/files/2020/03/f72/doe-fy2021-budget-volume-1_2. 73. See page 34. pdf. p119. 60 89. FY 2023 Congressional Budget Request – National 108. ‘Atomic Weapons Establishment’. Hansard, 19 Jul 2005: Nuclear Security Administration – Volume 1: Federal Column 59WS https://publications.parliament.uk/pa/ Salaries and Expenses Weapons Activities Defense cm200506/cmhansrd/vo050719/wmstext/50719m03. Nuclear Nonproliferation Naval Reactors’. Department of htm#50719m03.html_sbhd0 Energy, April 2022. https://www.energy.gov/sites/default/ 109. See Peter Burt. ‘AWE’. p15. for more details files/2022-05/doe-fy2023-budget-volume-1.pdf. p115. 110. Ibid. p16 90. Department of Energy. ‘FY 2022 Congressional Budget 111. Ministry of Defence. ‘MoD Major Projects Portfolio data Request’. p85. 2021’. 91. Department of Energy. ‘FY 2023 Congressional Budget 112. ‘ORION-Fact Sheet – Shaping the Future of Plasma Request’. p114. Physics’. AWE, 2013. https://www.awe.co.uk/app/ 92. Ibid. p118. uploads/2014/07/ORION-Fact_Sheet.pdf. 93. Department of Energy. ‘FY 2022 Congressional Budget 113. A petaflop is a unit used to measure computing power, Request’. p5,67. derived from the contraction FLOPS, meaning ‘floating 94. Department of Energy. ‘FY 2023 Congressional Budget point operations per second’. One petaflop is equal to one Request’. p91. thousand million million floating point operations (1015) 95. Department of Energy. ‘FY 2022 Congressional Budget per second. Request’. p89. 114. AWE. ‘AWE Names Its New Supercomputer “Vulcan” 96. Ibid. p67. in Honour of the RAF Aircraft’, 12 November 2019. 97. Ibid. p84. https://www.awe.co.uk/2019/11/awe-names-its-new- 98. Department of Defense ‘FY 2022 Budget Estimates’. p290. supercomputer-vulcan-in-honour-of-the-raf-aircraft/. 99. Department of Defense. ‘FY 2021 Budget Estimates’. p114. 115. TOP500. ‘AWE’. Accessed 4 July 2022. https://www. 100. ‘Fiscal Year 2022 Stockpile Stewardship and top500.org/system/179409/. Management Plan’. National Nuclear Security 116. Stephen Lovegrove. ‘Accounting Officer Assessment Administration (NNSA), March 2022. https://www. for UK/France TEUTATES Programme’, 4 February energy.gov/sites/default/files/2022-03/FY%202022%20 2019. https://assets.publishing.service.gov.uk/ SSMP%20March%202022.pdf. ch8 p32–33. This estimate government/uploads/system/uploads/attachment_data/ is based on the cost of the spending at the time it is file/778596/20190212_Accounting_Officer_Assessment_ incurred: ‘then-year dollars’. In 2022 dollars the cost for_the_TEUTATES_programme_MSU_4.2.4.6-Min_DP- estimate is between $8.9bn to $10.1bn. Penny_Young.pdf. 101. Adapted from Fiscal Year 2022 Stockpile Stewardship and 117. ‘France: Nuclear Weapons’. Hansard UIN 20361, 22 Management Plan. p2–11. See note 100. June 2021. https://questions-statements.parliament.uk/ 102. Department of Energy ‘FY 2021 Congressional Budget written-questions/detail/2021-06-22/20361. Request’. p295. 118. Lovegrove. ‘TEUTATES Accounting Officer Assessment’; 103. See Dan Sabbagh. ‘US Nuclear Warhead Standoff CEA. ‘UK/French Joint Technological Developments “Has Significant Implications for UK”’. the Guardian, EPURE’. Accessed 29 November 2021. http://www- 8 December 2020. http://www.theguardian.com/uk- teutates.cea.fr/uk/joint-technological-developments. news/2020/dec/08/us-nuclear-warhead-standoff-has- html. significant-implications-for-uk. 119. Reprinted by permission from Nature. Taken from 104. See, for example, Charles Richard. ‘Statement, February ‘Science of nuclear warheads’, O’Nions et al. © 2002. 415, 2020’; and ‘Department of Defense Background pages 853–857 (2002). Since the original publication the Briefing on Nuclear Deterrence and Modernization’. Orion laser has come online with a short-pulse capability. US Department of Defense, 21 February 2020. https:// 120. Managing Infrastructure Projects on Nuclear-Regulated www.defense.gov/Newsroom/Transcripts/Transcript/ Sites’. National Audit Office, 10 January 2020. p55. Article/2090986/department-of-defense-background- 121. https://questions-statements.parliament.uk/written- briefing-on-nuclear-deterrence-and-modernizati/. questions/detail/2022-02-21/126551/ 105. This summary is taken from a copy of the memo seen 122. Stephen Lovegrove. ‘Project Pegasus Accounting Officer by the Nuclear Information Service, entitled ‘W93/Mk7 Assessment’, 10 March 2021. https://assets.publishing. Navy Warhead – Developing Modern Capabilities to service.gov.uk/government/uploads/system/uploads/ Address Current and Future Threats’. attachment_data/file/973246/20210310_-_NWCSP__ 106. See page 38. Pegasus__AOA_-_2-_OS_1__Redacted.pdf. 107. See page 13. 61 123. 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Nuclear Weapons: Costs’. Hansard UIN 21808, 24 June 125. ‘Nuclear Weapons’. Hansard UIN 21807, 24 June 2021. 2021. https://questions-statements.parliament.uk/ https://questions-statements.parliament.uk/written- written-questions/detail/2021-06-24/21808. questions/detail/2021-06-24/21807 141. ‘Nuclear Weapons: Procurement’. Hansard UIN 20362, 22 126. ‘Nuclear Weapons: Expenditure’. Hansard UIN 21809, 24 June 2021. https://questions-statements.parliament.uk/ June 2021. https://questions-statements.parliament.uk/ written-questions/detail/2021-06-22/20362. written-questions/detail/2021-06-24/21809 142. Ministry of Defence. ‘Major Projects Portfolio Data 127. ‘The United Kingdom’s Future Nuclear Deterrent: The March 2022’. 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If the service life of a component is dated from the time government/uploads/system/uploads/attachment_data/ of manufacture and both UK and US components are file/767326/2018_Nuclear_Deterrent_Update_to_ part of a single production run, then its service life will Parliament.pdf. end at a particular calendar date, irrespective of when it 129. Ministry of Defence. ‘The United Kingdom’s Future was incorporated into a warhead. Nuclear Deterrent: The 2019 Update to Parliament’, 146. Ministry of Defence. ‘The 2016 Update to Parliament’. p5. 2019. http://data.parliament.uk/DepositedPapers/Files/ 147. ‘Trident Alternatives Review’. Cabinet Office, 16 DEP2019-1091/nuclear_Deterrent_2019Update_to_ July 2013. https://assets.publishing.service.gov.uk/ Parliament.pdf. government/uploads/system/uploads/attachment_data/ 130. ‘MoD Government Major Projects Portfolio data, 2018’. file/212745/20130716_Trident_Alternatives_Study.pdf. Ministry of Defence, 4 July 2018. https://www.gov.uk/ 148. 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See Nuclear Information Service. ‘AWE Becomes a Non- “in this Parliament or early in the next”, which at the Departmental Public Body’, 29 September 2021. https:// time would have scheduled the decision either before or www.nuclearinfo.org/article/awe-becomes-public-body/. soon after an election in May 2020. 153. ‘Nuclear Posture Review 2018’. Office of the Secretary of 133. Ministry of Defence. ‘The 2018 Update to Parliament’. p4. Defense, February 2018. https://media.defense.gov/2018/ 134. See the ‘W93 Antecedents’ section on page 40. Feb/02/2001872886/-1/-1/1/2018-NUCLEAR-POSTURE- 135. See the ‘W93 and Mk7 Programmes’ section on page 20 REVIEW-FINAL-REPORT.PDF. p38. and Figure 4. 154. Ibid. pVII. 62 155. ‘Fiscal Year 2019 Stockpile Stewardship and Management 165. ‘Global Britain in a Competitive Age: The Integrated Plan’. National Nuclear Security Administration (NNSA), Review of Security, Defence, Development and Foreign October 2018. https://www.energy.gov/sites/prod/ Policy’. HM Government, March 2021. https://assets. files/2018/10/f57/FY2019%20SSMP.pdf. ch1 p8. publishing.service.gov.uk/government/uploads/system/ 156. Office of the Secretary of Defense. ‘Nuclear Posture uploads/attachment_data/file/975077/Global_Britain_ Review 2018’. p30, 53–55. in_a_Competitive_Age-_the_Integrated_Review_of_ 157. See Russia Matters. ‘Is “Escalate to Deescalate” Part Security__Defence__Development_and_Foreign_Policy. of Russia’s Nuclear Toolbox?’, 8 January 2020. https:// pdf. p76. www.russiamatters.org/analysis/escalate-deescalate- 166. Ibid. p76–77. part-russias-nuclear-toolbox; Olga Oliker and Andrey 167. Ibid. p77. Baklitskiy. ‘The Nuclear Posture Review and Russian 168. HM Government. ‘Strategic Defence and Security “De-Escalation:” A Dangerous Solution to a Nonexistent Review 2015’. p35. Problem’. War on the Rocks, 20 February 2018. https:// 169. HM Government. ‘Global Britain in a Competitive Age’. warontherocks.com/2018/02/nuclear-posture-review- p76–77. The policy encompasses threats to both the UK russian-de-escalation-dangerous-solution-nonexistent- and its allies. problem/. 170. International Court of Justice. Legality of the Threat or 158. Office of the Secretary of Defense. ‘Nuclear Posture Use of Nuclear Weapons: Advisory Opinion of 8 July Review 2018’. p37. 1996. The Hague: International Court of Justice, 1996. 159. Ibid. 171. Nicholas Grief. ‘Legality of the Threat or Use of Nuclear 160. See ‘DOD Review Recommends Reduction in Nuclear Weapons’. International and Comparative Law Quarterly Force’. Office of Assistant Secretary of Defense, 22 46, no. 3 (July 1997): 681–88. https://doi.org/10.1017/ September 1994. http://missilethreat.csis.org/wp-content/ S0020589300060863. uploads/2022/01/1994-NPR-News-Release-Slides-Clinton. 172. Ian Davis. ‘The British Bomb and Nato: Six Decades of pdf; ‘Nuclear Posture Review [Excerpts]’. 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Last. ‘The Fog of War’. Washington 161. See Stephen Schwartz. ‘Ready, Aim, Fired: Can Biden Examiner, 18 May 2009. https://www. Rescue the Nuclear Posture Review?’ Bulletin of the washingtonexaminer.com/weekly-standard/the-fog-of- Atomic Scientists, 30 September 2021. https://thebulletin. war. org/2021/09/ready-aim-fired-can-biden-rescue-the- 175. Ralph Vartabedian. ‘Nuclear Weapon Retrofit Falters’. Los nuclear-posture-review/. Angeles Times, 29 May 2009. https://www.latimes.com/ 162. See Daryl G. Kimball. ‘Biden Policy Allows First Use of archives/la-xpm-2009-may-29-na-broken-warheads29- Nuclear Weapons’. Arms Control Association. Accessed story.html. 12 April 2022. https://www.armscontrol.org/act/2022-04/ 176. Jonathan Medalia. ‘Nuclear Warheads: The Reliable news/biden-policy-allows-first-use-nuclear-weapons. Replacement Warhead Program and the Life Extension 163. See https://crsreports.congress.gov/product/pdf/IF/ Program’. Congressional Research Service, 3 December IF12084; https://breakingdefense.com/2022/03/biden- 2007. https://sgp.fas.org/crs/nuke/RL33748.pdf. p29–33. administration-kills-trump-era-nuclear-cruise-missile- 177. For an overview of the plan see Department of Energy. program/ ‘Fiscal Year 2015 Stockpile Stewardship and Management 164. See the ‘UK warhead stockpile figures 1998–2015’ section Plan’. ch2 p13. on page 13. 178. ‘Nuclear Triad: DOD and DOE Face Challenges Mitigating Risks to U.S. Deterrence Efforts’. United States Government Accountability Office, May 2021. https://www.gao.gov/assets/gao-21-210.pdf. p33. 63 179. NNSA. ‘Fiscal Year 2019 Stockpile Stewardship and 195. See Tom Plant and Matthew Harries. ‘Going Ballistic: Management Plan’. p47. The UK’s Proposed Nuclear Build-Up’. Royal United 180. Charles A Richard. ‘Statement of Charles A. Richard Services Institute, 16 March 2021. https://www.rusi. Commander United States Strategic Command’. 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The Guardian. ‘UK Lobbies US to Support Controversial Nukewatch. Accessed 8 December 2018. http://www. New Nuclear Warheads’, 1 August 2020. http://www. nukewatch.org.uk/wp-content/uploads/2014/04/Convoy- theguardian.com/world/2020/aug/01/uk-trident-missile- log-2016.pdf; Nuclear Information Service. ‘Doubling of warhead-w93-us-lobby. Nuclear Transports May Indicate Delivery of Upgraded 218. RIA Novosti. ‘Russia to Revamp Air-Space Defenses by Warheads’. Accessed 12 January 2019. https://www. 2020 – Air Force Chief’, 14 August 2009. https://web. nuclearinfo.org/article/transport/doubling-nuclear- archive.org/web/20090814211437/http://en.rian.ru/ transports-may-indicate-delivery-upgraded-warheads. mlitary_news/20090811/155782307.html. 208. See the ‘Nuclear Warhead Capability Sustainment 219. A particularly high level of secrecy is applied to such Programme’ on page 23. measures, but Russia’s use of conventionally-armed 209. 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Department of Defense, beyond the short term and the true stockpile size will be February 2018. https://www.secnav.navy.mil/fmc/fmb/ substantially closer to Nukewatch’s best estimate. Documents/19pres/RDTEN_BA7_book.pdf. p101. 210. The speed of the apparent observed increases do not 221. See the ‘W93 Antecedents’ section on page 40. appear to allow for a long period of manufacturing 222. See the ‘Janus Faced: nuclear armed states under the components after the probable decision point in late NPT’ section on page 31. 2019 or early 2020. It is not possible to be certain, but the 223. See the ‘2018 US Nuclear Posture Review’ section on page rise to 260 may involve a returning of the entire stock of 27. dismantled warheads to service with the stockpile rising 224. See the ‘2018 US Interoperable Warheads and the 3+2 to the total number of Trident warheads in the initial plan’ section on page 18 for this detail and for further production run. See the ‘UK warhead stockpile figures background to this section. 1998–2015’ section on page 13. 225. Department of Defense. ‘FY 2021 Budget Estimates’. p114. 211. Ministry of Defence. ‘Request for Information under the gives the name as the ‘Interoperative Warhead’, but this Freedom of Information (FOI) Act – 25-03-2013-173601- appears to be a malapropism, as the correct name can be 014’, 25 July 2013. https://robedwards.typepad.com/files/ found in earlier budget documents. The previous years’ mod-foi-response-on-dismantling-nuclear-weapons.pdf. budget makes it clear that this project (3097 RDTEN) was 212. United Kingdom of Great Britain and Northern Ireland. for the first Interoperable Warhead IW1, which would ‘National Report’. have replaced the W88 and W78 (see ‘Fiscal Year (FY) 213. 2000 Review Conference of the Parties to the Treaty 2020 Budget Estimates – Research, Development, Test on the Non-Proliferation of Nuclear Weapons, & Evaluation, Navy – Justification Book Volume 5 of 5’. Final Document – Volume I (Parts I and II)’. United Department of Defense, March 2019. https://www.secnav. Nations, 10 May 2001. NPT/CONF.2000/28NPT/ navy.mil/fmc/fmb/Documents/22pres/RDTEN_BA7_ CONF.2000/28(PartsIandII). https://undocs.org/NPT/ Book.pdf. p117). CONF.2000/28(PartsIandII). p15. Commitment to these 226. The study appears to have been carried out between measures was reaffirmed in the 2010 Review Conference, October 2018 and March 2019 (see NNSA. ‘Fiscal Year see ‘2010 Review Conference of the Parties to the Treaty 2019 Stockpile Stewardship and Management Plan’. on the Non-Proliferation of Nuclear Weapons. Final ch2 p13; ‘FY 2020 Congressional Budget Request – Document . Volume I’. United Nations, 2010. https:// National Nuclear Security Administration – Federal undocs.org/NPT/CONF.2010/50(Vol.I). p21. Salaries and Expenses, Weapons Activities, Defense 214. Ibid. p20. Nuclear Nonproliferation, Naval Reactors. Volume 1’. 215. NNSA. ‘Fiscal Year 2022 Stockpile Stewardship and Department of Energy, March 2019. https://www.energy. Management Plan’. ch2 p10. gov/sites/default/files/2019/04/f62/doe-fy2020-budget- 216. See the ‘Likelihood of diverging from the W93 design’ volume-1.pdf. p86). section on page 44. 65 227. Derived from Fiscal Year 2015 Stockpile Stewardship 241. See R.E. Kidder. ‘Assessment of the Safety of US Nuclear and Management Plan and Fiscal Year 2022 Stockpile Weapons and Related Nuclear Test Requirements: A Stewardship and Management Plan. See notes 74 and Post-Bush Initiative Update’, 10 December 1991. https:// 100. doi.org/10.2172/10130593. 228. ‘FY 2023 Congressional Budget Request’. p430; 242. ‘W78 Replacement Program (W87-1): Cost Estimates and ‘Fiscal Year (FY) 2023 Budget Estimates – Research, Use of Insensitive High Explosives’. National Nuclear Development, Test & Evaluation, Navy – Justification Security Administration, December 2018. https:// Book Volume 5 of 5’. Department of Defense, April nukewatch.org/newsite/wp-content/uploads/2019/02/ 2022. https://www.secnav.navy.mil/fmc/fmb/ W78-Replacement-Program-Cost-Estimates-IHE.pdf. p9. Documents/23pres/RDTEN_BA7_Book.pdf. p286. 243. Department of Energy. ‘FY 2020 Congressional Budget 229. NNSA. ‘Fiscal Year 2022 Stockpile Stewardship and Request’. p231,235. Additive manufacturing is the term Management Plan’. p2–10,2–15. The latest Department used for a more advanced and larger-scale process of 3D of Energy budget anticipates Concept Assessment for printing. the first of these warheads beginning in FY 2027. See 244. See Charles Richard. ‘Statement, March 2022’. p22. Department of Energy. ‘FY 2023 Congressional Budget 245. See the ‘Rationale’ section on page 39. Request’. p115. 246. Aaron Mehta. ‘Inside America’s Newly Revealed Nuclear 230. Ibid. p279. Ballistic Missile Warhead of the Future’. Defense News, 231. ‘Fiscal Year 2019 Stockpile Stewardship and Management 24 February 2020. https://www.defensenews.com/smr/ Plan’. ch2 p3. nuclear-arsenal/2020/02/24/inside-americas-newly- 232. Department of Energy. ‘FY 2021 Congressional Budget revealed-nuclear-ballistic-missile-warhead-of-the-future/. Request’. p279. 247. Department of Defense ‘FY 2021 Budget Estimates’. p174. 233. NNSA. ‘Fiscal Year 2019 Stockpile Stewardship and 248. Aaron Mehta. ‘Inside America’s Newly Revealed Management Plan’. ch2 p3. Warhead’. 234. ‘FY 2021 Congressional Budget Request – National 249. A typical process of nuclear targeting will look to provide Nuclear Security Administration’. p279. a high certainty of inflicting enough blast damage to 235. Tom Z. Collina. ‘Future of ‘3+2’ Warhead Plan in Doubt’. destroy a desired list of targets. Greater accuracy allows Arms Control Association, May 2014. https://www. for warheads with a lower yield to be employed, while armscontrol.org/act/2014_05/Future-of-3-2-Warhead- retaining the same level of certainty. The accuracy of Plan-in-Doubt. the Trident system has increased as part of the D5LE life 236. Ibid. extension programme and there are projects underway 237. One option for the first RRW design was apparently to further increase its accuracy using multiple stars the W89: a warhead design that was explosively tested for error correction during flight and submarine before being cancelled after the end of the Cold war navigational data prior to launch. The Mk 4A arming, and had been suggested as a possible replacement for fusing and firing system also includes an air-burst fuse the W88 (see: Ian Hoffman. ‘Lab Officials Excited by that increases accuracy. The accuracy of the trident New H-Bomb Project’. Alameda Times-Star, 6 February system as a whole has therefore increased since the 2006. http://web.archive.org/web/20060209021533/ current warheads were originally produced. http://www.insidebayarea.com:80/oaklandtribune/ 250. Author’s interview with Brian Burnell, July 2021. See localnews/ci_3480733), but the final design was said to also Whitehouse and Hare. ‘Minutes of Evidence’. Q152, have included the SKUA9, a primary only previously where design case substantiation is mentioned as one of used to test various secondary designs (see David Biello. three key areas where the UK is reliant on the US. ‘Special Report: New Nukes Are Good Nukes?’ Scientific 251. See the ‘W93 design and characteristics’ section on page American. Accessed 2 November 2021. https://www. 43. scientificamerican.com/article/new-nukes-are-good- 252. Brian Burnell. Interview with the author, July 2021. nukes/.) 253. Ibid. 238. See the ‘W93 and Mk7 Programmes’ section on page 20. 254. The Summit and Sierra computers, housed at the Oak 239. Department of Energy. ‘FY 2019 Congressional Budget Ridge National Laboratory and the Lawrence Livermore Request’. p163. National Laboratory respectively, are the second and 240. See the ‘W93 and Mk7 Programmes’ section on page 21. third most powerful computers in the world. They are around 20 and 12 times more powerful than Vulcan. See https://www.top500.org/lists/top500/2021/11/ 66 255. See Annexe D. This experience will have doubtless 266. Department of Energy. ‘FY 2022 Congressional Budget contributed to the government’s alarm when they Request’. p89. learned, after negotiating the purchase of the C4 Trident 267. Department of Energy. ‘FY 2022 Congressional Budget missile, that they still faced the prospect of compatibility Request’. p84–85. divergence as the US was planning to upgrade Trident 268. Department of Energy. ‘FY 2021 Congressional Budget from the C4 to the current D5 model. See Suzanne Request’. p122. Doyle ‘The United States Sale of Trident to Britain, 269. Department of Defense. ‘FY 2021 Budget Estimates’. p114. 1977–1982: Deal Making in the Anglo-American Nuclear 270. Department of Defense. ‘FY 2022 Budget Estimates’. Relationship’. Diplomacy & Statecraft 28, no. 3 (3 July p290. 2017): 477–93. https://doi.org/10.1080/09592296.2017.13474 271. Ibid 47. 272. Ibid. p291. 256. See note 249. 273. NNSA. ‘Fiscal Year 2018 Stockpile Stewardship and 257. See, for example, the assurance in the UK’s report to the Management Plan’. ch2 p17. 2019 NPT Preparatory Committee that the Dreadnought 274. Ministry of Defence. ‘The 2016 Update to Parliament’. submarine programme was not an upgrade to the 275. ‘FY 2018 Congressional Budget Request – National UK’s capabilities: United Kingdom of Great Britain and Nuclear Security Administration – Federal Salaries Northern Ireland. ‘National Report’. p3. and Expenses, Weapons Activities, Defense Nuclear 258. Department of Defense. ‘FY 2022 Budget Estimates’ p261. Nonproliferation, Naval Reactors. Volume 1’. Department 259. See Annexe B. of Energy, May 2017. https://www.energy.gov/sites/ 260. A new plutonium facility to replace the existing A90 default/files/2017/05/f34/FY2018BudgetVolume1_1.pdf. complex was originally part of the NWCSP, and was p98. scheduled for construction in the late 2020s. If there 276. NNSA. ‘Fiscal Year 2018 Stockpile Stewardship and is a requirement to manufacture new pits for the Management Plan’. ch2 p17–18. replacement warhead, the project to construct building is 277. Department of Energy. ‘FY 2018 Congressional Budget likely included as part of the larger warhead programme. Request’. p98. 261. See, for example, ‘A Progressive Approach to a World 278. Ministry of Defence. ‘The 2016 Update to Parliament’. Free of Nuclear Weapons: Revisiting the Building Blocks 279. NNSA. ‘Fiscal Year 2018 Stockpile Stewardship and Paradigm’. United Nations, 30 March 2016. undocs.org/A/ Management Plan’. ch2 p18. CN.10/2016/WG.I/WP.3. 280. Department of Energy. ‘FY 2019 Congressional Budget 262. P5. ‘Joint Communiqué – P5 Conference, Paris’, 3 Request’. p107. December 2021. https://www.diplomatie.gouv.fr/IMG/ 281. Department of Energy. ‘FY 2021 Congressional Budget pdf/p5_statement_2_3-12-21_cle04ad34.pdf.; P5. ‘Joint Request’. p264. Statement of the Leaders of the Five Nuclear-Weapon 282. Department of Energy. ‘FY 2020 Congressional States on Preventing Nuclear War and Avoiding Arms Budget Request’. p110; Department of Energy. ‘FY 2022 Races’, 3 January 2022. https://www.whitehouse.gov/ Congressional Budget Request’. p215; Department of briefing-room/statements-releases/2022/01/03/p5- Energy. ‘FY 2023 Congressional Budget Request’. p442. statement-on-preventing-nuclear-war-and-avoiding- 283. Department of Energy. ‘FY 2019 Congressional Budget arms-races/. Request’. p134. 263. BBC News. ‘Fears over “Replace Trident Plan”’, 3 May 284. Department of Energy. ‘FY 2021 Congressional Budget 2005. http://news.bbc.co.uk/1/hi/uk_politics/vote_2005/ Request’. p299. frontpage/4508151.stm. 285. King, D.B., R.M. Fleming, E.S. Bielejec, J.K. McDonald, 264. Trident’. Hansard 14 Mar 2007: Column 299. https:// and G. Vizkelethy. ‘Test Simulation of Neutron Damage publications.parliament.uk/pa/cm200607/cmhansrd/ to Electronic Components Using Accelerator Facilities’. cm070314/debtext/70314-0005.htm. Nuclear Instruments and Methods in Physics Research 265. For an overview of this work see: Henrietta Wilson. Section B: Beam Interactions with Materials and Atoms ‘Disarmament Verification Research at AWE: What It Is, 365 (December 2015): 294–99. https://doi.org/10.1016/j. Why It’s There, and What Next’. Nuclear Information nimb.2015.08.026; ‘Boeing: Every Minute Counts’. Service. Accessed 4 December 2020. http://nis. Accessed 14 October 2021. https://www.boeing.com/ netuxosandbox.co.uk/blog/henrietta-wilson/2020/07/ features/2017/03/minuteman-03-17.page. disarmament-verification-research-awe-what-it-why-it’s- 286. Department of Energy. ‘FY 2020 Congressional Budget there-and-what/. Request’. p167. 67 287. Department of Energy. ‘FY 2021 Congressional Budget 309. Jeffrey Lewis. ‘FOGBANK’. Arms Control Wonk, 7 March Request’. p299. 2008. http://www.armscontrolwonk.com/archive/201814/ 288. Department of Energy. ‘FY 2019 Congressional Budget fogbank/. Request’. p81. 310. ‘Nuclear Triad: DOD and DOE Face Challenges 289. Ibid. p158. Mitigating Risks to U.S. Deterrence Efforts’. Government 290. Department of Energy. ‘FY 2022 Congressional Accountability Office, May 2021. https://www.gao.gov/ Budget Request’. p245.; Sandia National Laboratories. assets/gao-21-210.pdf. p34–35. ‘Centrifuge/Superfuge – Validation and Qualification 311. Jonathan V. Last. ‘The Fog of War’. Washington Sciences Experimental Complex’. Accessed 22 October Examiner, 18 May 2009. https://www. 2021. https://www.sandia.gov/vqsec/facilities/centrifuge/. washingtonexaminer.com/weekly-standard/the-fog-of- 291. Department of Energy. ‘FY 2022 Congressional Budget war. Request’. p245. 312. Ralph Vartabedian. ‘Nuclear Weapon Retrofit Falters’. Los 292. Department of Energy. ‘FY 2020 Congressional Budget Angeles Times, 29 May 2009. https://www.latimes.com/ Request’. p115. archives/la-xpm-2009-may-29-na-broken-warheads29- 293. Department of Energy. ‘FY 2021 Congressional Budget story.html. Request’. p556; ‘Fiscal Year 2020 Stockpile Stewardship 313. Government Accountability Office. ‘Nuclear Triad: DOD and Management Plan’. National Nuclear Security and DOE Face Challenges’. p43. Administration (NNSA), July 2019. https://www.energy. 314. Ibid. p35. gov/sites/default/files/2019/08/f65/FY2020__SSMP.pdf. 315. See Annexe C. ch4 p29. 316. Brian Burnell. Interview with the author. 294. Mark Rockwell. ‘Nuclear Weapons Security Agency 317. ‘Fiscal Year 2018 Stockpile Stewardship and Management Moving Apps to Cloud’. FCW, 1 August 2019. https://fcw. Plan’. US Department of Energy, November 2017. com/articles/2019/08/01/nnsa-cloud-rockwell.aspx. https://www.energy.gov/sites/default/files/2017/11/ 295. Department of Energy. ‘FY 2021 Congressional Budget f46/fy18ssmp_final_november_2017%5B1%5D_0.pdf. Request’. p549. p2–10,2–13. 296. Department of Energy. ‘FY 2020 Congressional Budget 318. Ibid. p59;‘Department of Energy FY 2019 Congressional Request’. p110. Budget Request’. p74. 297. Department of Energy. ‘FY 2019 Congressional Budget 319. ‘Department of Defense Fiscal Year (FY) 2020 Request’. p158. Budget Estimates – Research, Development, Test & 298. Ibid. p86. See also Philpott, W.J., and R. Jones. ‘AWG-711, Evaluation, Navy – Justification Book Volume 5 of 5’, a Type C Transport Package’. France, 2019; and Douglas March 2019. https://www.secnav.navy.mil/fmc/fmb/ James Ammerman, David C. Harding, and Daniel Villa. Documents/22pres/RDTEN_BA7_Book.pdf. p118. ‘AWG 711 Package Development Program at Sandia.’ 320. See NNSA.‘Fiscal Year 2015 Stockpile Stewardship and Sandia National Lab. (SNL-NM), Albuquerque, NM Management Plan’. ch1 p4, where it is also known as the (United States); Sandia National Laboratories., 1 June ‘W78/88-1 warhead’. The W88 was already planned to 2009. https://www.osti.gov/biblio/1141566. undergo the Alt 370, so it may have been the intention 299. Department of Energy. ‘FY 2022 Congressional Budget that some or all of the W88 stockpile would remain in Request’. p225; Department of Energy. ‘FY 2023 service alongside the IW1 until subsequent Interoperable Congressional Budget Request’. p454. Warheads were built. 300. Department of Energy. ‘FY 2023 Congressional Budget 321. ‘Department of Energy FY 2019 Congressional Budget Request’. p138. Request’. p93. 301. Department of Defense. ‘FY 2022 Budget Estimates’. 322. NNSA. ‘Fiscal Year 2019 Stockpile Stewardship and p262. Management Plan’. p44. 302. Ibid. p262, 275. 323. Department of Defense. ‘FY 2022 Budget Estimates’ 303. See Charles Richard. ‘Statement, February 2020’. p11. lists the feasibility study as having run throughout the 304. Department of Defense. ‘FY 2022 Budget Estimates’. calendar year 2020, but this is almost certainly an error p275. as it doesn’t fit with other known dates. See note 226 and 305. Department of Defense. ‘FY 2021 Budget Estimates’ p101. Department of Energy. ‘FY 2021 Congressional Budget 306. Department of Defense. ‘FY 2022 Budget Estimates’. Request’. p123. p276. 307. Ibid. p275. 308. Ibid. p277. 68 324. In November 2017 the IW1 was due to begin Studies and Engineering in FY 2020, with baseline costs being calculated in FY 2024 and warhead production running from FY 2030 to FY 2041 (see NNSA. ‘Fiscal Year 2018 Stockpile Stewardship and Management Plan’). In July 2019, when the IW1 has become the W87-1, the IW2/ BM-Y is known as the “Next Navy Warhead”, but Studies and Engineering were not due to start until FY 2024. However, the production dates from that time of 2034 to 2041 (see NNSA. ‘Fiscal Year 2020 Stockpile Stewardship and Management Plan’) are similar to current plans for the W93, which anticipates production beginning between 2034 and 2036 (see NNSA. ‘Fiscal Year 2022 Stockpile Stewardship and Management Plan’.). 325. Department of Energy. ‘FY 2023 Congressional Budget Request’. p430; Department of Defense. ‘FY 2023 Budget Estimates’. p286. 326. Ibid. p288; 317. 69 Glossary 3+2 Plan – Initiative under the Obama administration NPR – US Nuclear Posture Review. A series of reviews to consolidate the US nuclear weapon stockpile to five setting US nuclear posture under different presidential designs. administrations. Aeroshell – Heat-proof shield that prevents damage NPT – Treaty on the Non-Proliferation of Nuclear during re-entry into earth’s atmosphere. The term is Weapons, commonly referred to as the Non- also used to refer to an entire re-entry body or vehicle. Proliferation Treaty. AWE – UK Atomic Weapons Establishment, where the NWCSP – Nuclear Warhead Capability Sustainment UK’s nuclear weapons are designed, built and serviced. Programme. Chevaline – Historical UK-designed warhead, Polaris – Historical US SLBM, also operated by the UK. mounted on Polaris missiles. Primary – Part of a thermonuclear warhead that D5LE2 – Planned second life-extension programme provides the initial explosive yield through a fission for the Trident D5 missile reaction. DOD – US Department of Defence. Re-entry body/vehicle – Heat-shielded craft designed DOE – US Department of Energy to carry a warhead during its re-entry and descent Holbrook – Name sometimes used for the original UK onto its target. Trident warhead. Replacement Warhead Programme – Programme to Hydrodynamics – The study of the behaviour of build a new UK nuclear warhead. While not officially materials which display fluid properties. Used to refer confirmed, there are indications this is the programme to explosive experiments used in warhead design. name used within government. ICJ – International Court of Justice. RRW – Reliable Replacement Warheads. A putative IR – The 2021 Integrated Review of Security, Defence, series of new warheads planned under the George W. Development and Foreign Policy followed the previous Bush administration. SDR/SDSRs in updating the UK’s nuclear posture. Secondary – Part of a thermonuclear warhead IW1 – Interoperable Warhead 1. Putative US warhead, providing an explosive yield through fusion, after intended to be the first new warhead under the 3+2 plan. the primary explosion. Generally responsible for the JTD – Joint Technology Demonstrator, a US-UK majority of the yield. warhead development project. SDR – 1998 Strategic Review, set out the UK’s nuclear kt – kiloton. A unit of explosive power used to posture under the Blair government. measure the yield of nuclear weapons. Equivalent to SDSR – The 2010 Strategic Defence and Security 1,000 tons of TNT. Review and the 2015 joint SDSR and National Security LEP – Life Extension Programme. Strategy updated the UK’s nuclear posture. MDA – 1958 Mutual Defence Agreement. US-UK treaty SLBM – Submarine Launched Ballistic Missile. for the sharing of nuclear information and materials. SSBN – Ship Submersible Ballistic Nuclear. NATO Later supplemented by the 1963 Polaris Sales Agreement. designation for a nuclear-armed and nuclear-powered MIRV – Multiple Independent Re-entry Vehicle(s). submarine. System for mounting several warheads, which are Surety – Measures to prevent unauthorised assigned different targets, on a single missile. detonation of a warhead and maximise the reliability Mk4A – Re-entry body fitted to the W76 as part of the of authorised use. W76-1 life-extension. Also used to refer to the UK version Trident D5 – US SLBM. Currently undergoing a of this life extension programme and warhead variant. life-extension programme, with the further D5LE2 MOD – UK Ministry of Defence. planned. NEP – Nuclear Explosives Package. NNSA – Nuclear National Security Administration For US warhead and aeroshell designations, please refer to Figure 3 on p19 and Figure 8 on p41. 70 Acknowledgements Nuclear Information Service (NIS) would like to thank This work has been made possible by grant funding the author, David Cullen, for his work in researching, and we are very grateful to the Network for Social drafting and editing this report. Sincere gratitude Change, Joseph Rowntree Charitable Trust, Greenpeace also to the project team: Nick Ritchie, Ailsa Johnson, Environmental Trust and all our individual donors. 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We investigate the UK nuclear weapons programme and publish accurate and reliable information to stimulate informed debate on disarmament and related issues. Nuclear Information Service 35–39 London Street Reading, Berkshire rG1 4PS United Kingdom +44 (0)118 327 4935 [email protected] www.nuclearinfo.org Twitter: @Nuclearinfo Facebook: www.facebook.com/Nuclearinfo iSBN 978-1-9993413-3-6 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0), except images and figures as noted. The Ministry of Defence retains the copyright to all images in this report credited to the MOD. The images are licensed under the Open Government License v3.0. 72 Previous NIS publications Previous publications can be found at British Military Attitudes to Nuclear Weapons and www.nuclearinfo.org/reports Disarmament A joint report with Nuclear Education Trust highlights Some reports are also available to order as hard copies concerns about the costs and role of the Trident at https://form.jotform.com/203293750177053 programme. June 2015 Nuclear Weapon Modernisation: Attitudes of non- nuclear weapon states Reform Not Renewal Compilation and analysis of statements to UN on the The US-UK Mutual Defence Agreement: How it works, subject of nuclear modernisation. and why it needs to be reformed iSBN 978-1-9993413-1-2 May 2014 August 2021 Atoms for Peace Trouble Ahead: Risks and Rising Costs in the UK Joint study with Medact investigating research links Nuclear Weapons Programme between British universities and the Atomic Weapons Identifies problems arising in the UK nuclear weapons Establishment programme, the overall total costs and need for policy February 2014 changes. iSBN 978-1-9993413-0-5 Radiation (Emergency Planning And Public April 2019 Information) Regulations 2001 (REPPIR) The Lay-Person’s alternative guide to REPPIR, Playing With Fire: Nuclear Weapons Incidents and relating to The Atomic Weapons Establishment Accidents in the United Kingdom Aldermaston and Burghfield. A Large Associates report Listings and details of 110 known accidents and commissioned by NIS. incidents in the UK’s nuclear weapons programme 2012 over its 65 year history. February 2017 Opening the Gates Raising the standard of community liaison at the AWE: Britain’s Nuclear Weapons Factory – Past, Atomic Weapons Establishment. Present, And Possibilities For The Future 2011 Describes AWE’s history, current work and possible diversification in the event of a future cancellation of Project Hydrus the Trident programme A briefing on AWE Aldermaston’s new hydrodynamics June 2016 research facility. 2010 What does NATO need from Britain? Explores UK potential contributions to the Alliance in Swamped! the light of emerging geopolitical, technological and The devastating impact of the July 2007 floods on strategic threats Britain’s nuclear weapons factories. February 2016 September 2008 73 Nuclear Information Service 35–39 London Street Reading, Berkshire rG1 4PS United Kingdom +44 (0)118 327 4935 [email protected] www.nuclearinfo.org iSBN 978-1-9993413-3-6 74