Although it initially conducted its own research, the United Kingdom later sent several scientists to Los Alamos to contribute to the Manhattan Project. But following the war, and the passing of the Atomic Energy Act in the United States, the United Kingdom decided to build its own bomb. This program was led by William G. Penney, a British scientist who had worked on the Manhattan Project at Los Alamos and sat on the targeting committee that chose the target cities of Hiroshima and Nagasaki.

While the U.K decision to develop nuclear weapons was partly due to prestige, it was also a means of creating an alternative decision making center. The theory was that by establishing two, entirely independent, centers of decision making, the Soviet Union would have to consider a possible response from both London and Washington should it decide to carry out a first strike. But in order for this theory to prove effective, the U.K. deterrent would have to be completely independent from the United States.

Current Force Configuration

The United Kingdom's nuclear forces today are entirely sea-based and comprise four Vanguard-class nuclear submarines that each carry up to 16 Trident D-5 submarine launched ballistic missiles. Four submarines are believed to be the minimum required to carry out continuous at-sea deterrence while allowing for long refits and sufficient rest between patrols. While the submarines are designed and constructed in the United Kingdom, the Trident missile is purchased directly from the United States - a process that is deemed to be more economical as it allows the United Kingdom to "exploit American economies of scale."[1] Furthermore, the U.K. nuclear warhead, although independent, is based on the American W76 design.[2]

Britain's strategic submarine fleet is based at Her Majesty's Naval Base Clyde, Scotland, while its operational nuclear warheads are stored at the nearby Coulport ammunition base. Although the United Kingdom does not design its own ballistic missile, it is the Atomic Weapons Establishment (AWE) at Aldermarston that is required to design, build and maintain the U.K. nuclear warhead.[3] The strategic submarine fleet has been the key component of the U.K. deterrent since 1962 when President Kennedy offered Harold Macmillan the Polaris submarine-launched missile system.

Modernization

Although the United Kingdom has no plans to expand its strategic deterrent, it is planning to replace the existing Trident-carrying nuclear submarines with what it calls a "like-for-like" system (essentially the same delivery platform but in modernized form). It was estimated in 2006 that this would cost between GBP 15-20 billion.[4] The decision was first presented to the U.K. parliament in December 2006 by former Prime Minister Tony Blair and laid-out in the 2006 White Paper entitled "The Future of the United Kingdom's Nuclear Deterrent." Given that the current Vanguard-class submarines are likely to begin leaving service by the early 2020s, and it will take around 17 years "to design, manufacture and commission a replacement submarine," it was necessary to make a decision at the start of 2007.[5]

Although it was eventually decided that a replacement in the form of four Trident carrying SSBNs would be necessary, the 2006 White Paper did lay out a number of alternative options. These included: large aircraft equipped with cruise missiles; land-based ballistic missiles; and both surface and sub-surface sea-based options.[6] It was deemed that none of the other three options provided the same level of deterrence or sufficient financial savings to offset their inferior capabilities. In addition, the cost of developing cruise missiles to carry a nuclear warhead would exceed that of purchasing the Trident D-5 missile from the United States.[7]

While the initial decision to build a new class of submarines was taken in 2006, the current coalition government has delayed making a final "main gate" spending decision until 2016 (after the next general election). Once this decision has been made, it will be financially problematic to adapt any investment commitments. This delay was announced in the U.K. Strategic Defense and Security Review (SDSR) published in October 2010. The postponement of the project has been largely attributed to the UK’s overstretched defense budget and the belief that a delay will save money. [8] Commentators point to the influence of the Liberal Democrats - the junior partner in the UK’s coalition government - as an explanation; the Liberal Democrats have been very critical of the decision to replace the current naval deterrent with a "like-for-like" system and believe that cheaper alternatives have not been given due consideration.

To ensure the safety and viability of their nuclear weapons stockpile - while adhering to the Comprehensive Nuclear Test Ban Treaty - the UK and France signed a bilateral agreement in November 2010 that will allow for cooperation in this area. [9] Joint activities will involve the construction of a simulation facility in Valduc, France, where scientists from both countries will conduct work on the safety and security of their respective countrys' warheads. A joint Technology Development Center will also be established in Aldermaston, UK, to develop simulation technology for the center at Valduc. It is estimated that the Valduc facility will become operational around 2014 with construction costs to be split equally between France and the United Kingdom. [10]

Force Posture and Doctrine

The U.K. nuclear deterrent is assigned to NATO and its primary function is to contribute to the Alliance's collective defense. It has performed this role since 1962 when the United Kingdom agreed to purchase the Polaris ballistic missile system from the United States. Although the four Vanguard-class submarines and their Trident missiles are fully assigned to the Supreme Allied Commander Europe (SACEUR), they remain independent due to the nature of NATO command and control systems, which allow British commanders to communicate with both NATO and U.K. authorities.[11] As a result, SACEUR commands can be overruled if it's in the national interest to do so.

Although the United Kingdom no longer maintains tactical nuclear weapons, the 1998 Strategic Defense Review (SDR) did suggest that the Trident missiles could be given a "sub-strategic" role if required. The term "sub-strategic" has been used on numerous occasions in the past, but it has now been dropped from U.K. nuclear weapons doctrine. The end to Trident's sub-strategic role was announced by Defence Secretary Des Browne in 2007 when he stated that "we have deliberately chosen to stop using the term 'sub-strategic Trident." [12] This decision, and the insistence that nuclear weapons would only be used in the most extreme circumstances, reflects the 1996 Advisory Opinion from the International Court of Justice (ICJ).[13]

The 2010 SDSR gave, for the first time, an assurance that the United Kingdom "will not use or threaten to use nuclear weapons against non-nuclear weapon states parties to the NPT." [14] However, the document also emphasizes that the assurance does not apply to any state deemed to be "in material breach" of its nonproliferation obligations. [15] This language is reflective of the United States’ 2010Nuclear Posture Review, which provides a similar assurance and caveat. In addition, the SDSR states that the UK will retain a degree of calculated ambiguity by remaining "deliberately ambiguous about precisely when, how and at what scale" it would contemplate the use of its nuclear weapons. [16] In support of this declaratory policy, the UK maintains a minimal nuclear force that would only be used in "the most extreme circumstance of self defence," including the defense of NATO allies. [17]

U.K.-U.S. Cooperation

Although Anglo-American cooperation was prevalent during the war years, scientific collaboration was halted once the war ended. This was primarily due to U.S. fears over the transfer of knowledge and technology to third parties. But this policy was reversed in 1958 when the U.S. congress passed the Mutual Defense Agreement (MDA), which was primarily a response to the Soviet Union launching Sputnik in 1957. The United States feared that it was falling behind in the arms race and would benefit from a pooling of resources and expertise with the United Kingdom. Since that time, the MDA has allowed the United Kingdom to acquire U.S. weapon engineering expertise, warhead design, weapon components that can be more economically produced in the United States, delivery systems, and testing facilities.[18] In return, the United States has benefited from high-level scientific collaboration and access to U.K. military bases. Technical exchanges between scientists largely took place within the framework of a series of Joint Working Groups (JOWOGs).[19] These groups are still in existence today with both countries benefiting from a "crosscurrent of ideas and information."[20]

There have been occasions on which Anglo-American relations have been strained - perhaps most notably during the 1956 Suez Crisis - but these problems were overcome. This was demonstrated at the Nassau meeting between President Kennedy and Prime Minister Macmillan in 1962, where Kennedy stated that the United States would be canceling the Skybolt missile system (which the United Kingdom was going to purchase) due to high cost and poor test results. This led to Kennedy offering to sell Britain the Polaris missile system, which would be carried by U.K. submarines – an arrangement that further strengthened the bilateral nuclear relationship.[21]

Today cooperation is also evident at the operational level. When the U.K. submarines are commissioned they visit the U.S. naval base at King's Bay, Georgia, to load their Trident missiles before heading back to the Royal Ammunition depot at Coulport, Scotland, to load nuclear warheads. All of the U.K. Trident missiles are also serviced in the United States.

Arms Reductions

During the cold war the United Kingdom maintained a strategic diad that comprised both sea- and air-based capabilities. It is estimated that in 1989 the United Kingdom had around 180 tactical weapons primarily in the form of WE-177 free-fall bombs that could be dropped from Tornado aircraft.[22] However, all WE177 gravity bombs were retired prior to the Labour government's 1998 Strategic Defence Review (SDR). In 1989 the United Kingdom also possessed an estimated 20-30 WE-177C nuclear depth bombs, which were destroyed in 1992.[23]

The 1998 U.K. Strategic Defence Review concluded that each of the Vanguard-class nuclear submarines should carry a maximum of 48 warheads - a significant reduction from the previous maximum of 96. Furthermore, as part of the 2006 decision to replace the Vanguard-class submarines, former Prime Minister Tony Blair announced that the United Kingdom was implementing a further 20 percent cut in its operational warheads to less than 160. Foreign Secretary William Hague also stated in May 2010 that the United Kingdom intends to possess a total stockpile of no more than 225 nuclear warheads. [24] The most recent UK reductions were outlined in the 2010 SDSR, which contains a commitment to reduce the number of operational warheads onboard each Trident nuclear submarine from 48 to 40, to reduce the number of total operational warheads from 160 to 120, and to reduce the overall stockpile to no more than 180 nuclear warheads. [25]

Disarmament

Despite the initial 2006 decision to replace its existing Trident delivery platform, the United Kingdom has been perhaps the strongest supporter of multilateral disarmament from among the nuclear weapon states. It currently has the smallest number of deployed nuclear warheads and has cut its nuclear weapons arsenal quite considerably since the end of the cold war. Its reliance on only one delivery platform, coupled with the more marginal role that nuclear weapons play in the country's defense strategy, means that it would be easier for Britain to cease to be a nuclear power than any of the other nuclear weapons countries.[26] In addition to its arms reductions, the United Kingdom has been a vocal supporter of multilateral disarmament, with individuals such as Margaret Beckett (former foreign minister), David Miliband (former foreign minister) and Des Browne (former defence secretary) all speaking in favor of multilateral and incremental disarmament during their period as ministers.[27] All indications are that the current coalition government will maintain this policy.

The United Kingdom, in partnership with Norway, has also been carrying out technical research into the verification of nuclear disarmament at the Atomic Weapons Establishment in Aldermartson. It is hoped that the research being conducted will enable non-nuclear weapons states to inspect warhead dismantlement without any inadvertent transfer of sensitive information. This will be done largely by creating information barriers and utilizing non-destructive assay techniques.[28] Both the United Kingdom and Norway presented an update to their findings at the 2010 Review Conference of the Nuclear Non-Proliferation Treaty.

Civilian Nuclear Sector

In comparison to France, the United Kingdom's nuclear energy sector is relatively small, accounting for only 18 percent of electricity generation.[29] This more marginal contribution is due, in large part, to domestic oil and gas reserves in the North Sea. However, the depletion of these resources means that the United Kingdom will become more dependent on imports - placing greater emphasis on the need for a secure energy supply.[30] This, coupled with the fact that the government wishes to curb the country's greenhouse gas emissions by 60-80 percent by 2050, means that there is a requirement for a significant expansion in nuclear energy.[31] As a result, the government's 2006 energy review acknowledged the need to replace Britain's current nuclear energy infrastructure as and when required. There are currently 19 nuclear reactors in the United Kingdom, with the majority of these due to close by 2023. The 2006 report stated that they would be replaced with a new generation of reactors that the private sector will "initiate, fund, construct and operate."[32] In 2009 10 sites were named by the government as part of a policy that will include a large expansion in renewable energy and the use of so-called clean coal. It also appears likely that a further expansion of nuclear power will be needed if the United Kingdom is to meet its ambitious emission targets.

Fuel Cycle Facilities

The United Kingdom imports its uranium supplies but is largely self-sufficient in all other areas of the nuclear fuel cycle. Its facilities can be categorized as follows:

• Conversion - Carried out at Springfields and managed by Westinghouse under contract to the Nuclear Decommissioning Authority.[33]

• Deconversion - Urenco is planning to build a deconversion plant at Capenhurst with operation due to begin in 2014. It will treat uranium tails from all three Urenco sites at Capenhurst, Almelo in the Netherlands, and Gronau in Germany.

• Enrichment - Carried out by Urenco at its centrifuge plant at Capenhurst. This was previously the site of the gaseous diffusion plant that enriched uranium for defense purposes.

• Fuel Fabrication - Takes place at Springfields and includes Magnox, AGR and PWR fuels.

• Reprocessing - Undertaken at Sellafield, Cumbria. The THORP plant previously took spent fuel from international customers and is expected to remain in operation until at least 2016.

• Waste - The Nuclear Decommissioning Authority (NDA) is responsible for cleaning up the United Kingdom's legacy of nuclear waste at reactor sites, reprocessing plants and research facilities. Nuclear waste is currently being stockpiled above ground at short-term facilities at Sellafield.[34]

Sellafield

The United Kingdom possesses a significant reprocessing capability that is performed at Sellafield, Cumbria, on England's north-west coast. Its Thermal Oxide Reprocessing Plant (THORP) has been in operation since 1994 and is scheduled to close in 2016.[35] It was originally built to provide reprocessing services for international customers following a worldwide expansion in the use of nuclear power, but the level of expansion predicted was never fully realized. Sellafield has been the subject of long-running environmental concerns, particularly with regards to the local marine environment. The site contains a number of disused reactors and the storage pond in Building B30 is said to contain old reactor parts and decaying fuel rods, many of which have now turned to sludge and emit large doses of radiation.[36] It has been suggested that the clean-up operation at Sellafield may cost up to GBP 50bn over the next 100 years.[37]

Fissile Material

According to the United Kingdom's 2009 declaration to the IAEA Board of Governors, on 31 December 2008 it possessed 104.7 tons (t) of separated plutonium in product stores at reprocessing plants.[38] This material is largely being held at Sellafield. In addition, there were 1.9t of plutonium in unirradiated MOX fuel or other forms at reactor sites and 1.1t held elsewhere.[39] Plutonium contained in spent fuel at civilian reactor sites was estimated at 7t and a further 28t of plutonium was contained in spent fuel at reprocessing plants. Less than 500kg of plutonium was contained in spent fuel held elsewhere. This brings the total amount of plutonium held in spent fuel on 31 December 2008 to 35t.[40] The United Kingdom currently faces a dilemma about what to do with its plutonium stocks. Three long-term options are being considered: conversion to MOX fuel; immobilization as waste; and part immobilization.[41]

The United Kingdom had previously obtained its supplies of highly enriched uranium (HEU) for defense purposes from the gaseous diffusion plant at Capenhurst. Today it continues to use HEU for weapons purposes, naval propulsion reactors and test reactors.[42] According to its 2009 declaration to the IAEA on plutonium holdings, the United Kingdom has the following stocks of HEU: 347kg stored at fabricating plants and reprocessing facilities; 923kg stored at locations other than civil reactor sites, enrichment fabricating and reprocessing plants (e.g. labs and research centers); 10kg of irradiated HEU at civil reactor sites; and 131kg of irradiated HEU at locations other than civil reactor sites. This brings the U.K. total inventory of HEU holdings to 1,412kg.[43]

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[1] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[2] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[3] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[4] The Secretary of State for Defence and the Secretary of State for Foreign and Commonwealth Affairs, "The Future of the United Kingdom's Nuclear Deterrent, the U.K. Government, www.mod.uk, December 2006.
[5] The Secretary of State for Defence and the Secretary of State for Foreign and Commonwealth Affairs, "The Future of the United Kingdom's Nuclear Deterrent, the U.K. Government, www.mod.uk, December 2006.
[6] The Secretary of State for Defence and the Secretary of State for Foreign and Commonwealth Affairs, "The Future of the United Kingdom's Nuclear Deterrent, the U.K. Government, www.mod.uk, December 2006.
[7] The Secretary of State for Defence and the Secretary of State for Foreign and Commonwealth Affairs, "The Future of the United Kingdom's Nuclear Deterrent, the U.K. Government, www.mod.uk, December 2006.
[8] "Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review," Her Majesty's Government, October 2010, www.direct.gov.uk, p. 38.
[9] "UK-France Summit 2010 Declaration on Defence and Security Cooperation," 10 Downing Street, 2 November 2010, www.number10.gov.uk.
[10] "Cameron and Sarkozy hail UK-France defence treaties," BBC News, 2 November 2010, www.bbc.co.uk.
[11] John Simpson, "The United Kingdom and the Nuclear Future: The Strength of Continuity and the Chance for Change," Nonproliferation Review, Vol. 14, No. 2, July 2007.
[12] Speech by Des Browne "The United Kingdom's Nuclear Deterrent in the 21st Century," King's College London, 25 January 2007.
[13] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[14] "Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review," Her Majesty's Government, October 2010, www.direct.gov.uk, p. 38.
[15] "Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review," Her Majesty's Government, October 2010, www.direct.gov.uk, p. 38.
[16] "Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review," Her Majesty's Government, October 2010, www.direct.gov.uk, p. 37.
[17] "Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review," Her Majesty's Government, October 2010, www.direct.gov.uk, p. 37.
[18] John Simpson and Jenifer Mackby, "The Special Nuclear Relationship," in "U.S.-UK Nuclear Cooperation After 50 Years," Jenifer Mackby and Paul Cornish (eds.), (Washington: Center for Strategic and International Studies, 2008).
[19] John Simpson and Jenifer Mackby, "The Special Nuclear Relationship," in "U.S.-UK Nuclear Cooperation After 50 Years," Jenifer Mackby and Paul Cornish (eds.), (Washington: Center for Strategic and International Studies, 2008).
[20] John Simpson and Jenifer Mackby, "The Special Nuclear Relationship," in "U.S.-UK Nuclear Cooperation After 50 Years," Jenifer Mackby and Paul Cornish (eds.), (Washington: Center for Strategic and International Studies, 2008).
[21] John Simpson and Jenifer Mackby, "The Special Nuclear Relationship," in "U.S.-UK Nuclear Cooperation After 50 Years," Jenifer Mackby and Paul Cornish (eds.), (Washington: Center for Strategic and International Studies, 2008).
[22] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[23] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[24] The Secretary of State for Defence and the Secretary of State for Foreign and Commonwealth Affairs, "The Future of the United Kingdom's Nuclear Deterrent, the U.K. Government, www.mod.uk, December 2006; Richard Norton-Taylor, "Britain's nuclear arsenal is 225 warheads, reveals William Hague," The Guardian, 26 May 2010, www.guardian.co.uk.
[25] "Securing Britain in an Age of Uncertainty: The Strategic Defence and Security Review," Her Majesty's Government, October 2010, www.direct.gov.uk, p. 38.
[26] Sir Lawrence Freedman, "British Perspectives on Nuclear Weapons and Nuclear Disarmament," in Barry Blechman (ed), "Unblocking the Road to Zero," Henry L. Stimson Center, February 2009.
[27] Margaret Beckett, "Keynote Address: A World Free of Nuclear Weapons?" Carnegie International Nonproliferation Conference, www.carnegieendowment.org; Des Browne, "Laying the Foundations for Multilateral Disarmament," Address to the Conference in Disarmament in Geneva, www.mod.uk, 5 February 2008; David Miliband, "A World Without Nuclear Weapons," The Guardian, www.guardian.co.uk, 8 December 2008.
[28] Cristina Hansell, "Full-Scale Exercise Mocking Up Non-Nuclear State Verification of Nuclear Warhead Dismantlement Held," CNS Feature Story, cns.miis.edu, 21 July 2009.
[29] "Nuclear Power in the United Kingdom," World Nuclear Association, April 2010, www.world-nuclear.org.
[30] "The Energy Challenge: Energy Review Report 2006," Department of Trade and Industry, news.bbc.co.uk, July 2006.
[31] Paul Eccleston, "Labour Conference: Gordon Brown says CO2 targets must be raised to 80% by 2050," The Daily Telegraph, www.telegraph.co.uk, 23 September 2008.
[32] "The Energy Challenge: Energy Review Report 2006," Department of Trade and Industry, news.bbc.co.uk, July 2006.
[33] "Nuclear Power in the United Kingdom," World Nuclear Association, April 2010, www.world-nuclear.org.
[34] "Nuclear Power in the United Kingdom," World Nuclear Association, April 2010, www.world-nuclear.org.
[35] Martin Forwood, "The Legacy of Reprocessing in the United Kingdom," International Panel on Fissile Materials, www.fissilematerials.org, July 2008.
[36] Robin McKie, "Sellafield: the most hazardous place in Europe," www.guardian.co.uk, 19 April 2009.
[37] Robin McKie, "Sellafield: the most hazardous place in Europe," www.guardian.co.uk, 19 April 2009.
[38] "Communication Received from the United Kingdom of Great Britain and Northern Ireland Concerning its Policies Regarding the Management of Plutonium," INFCIRC/549/Add.8/12, www.iaea.org, 15 September 2009.
[39] "Communication Received from the United Kingdom of Great Britain and Northern Ireland Concerning its Policies Regarding the Management of Plutonium," INFCIRC/549/Add.8/12, www.iaea.org, 15 September 2009.
[40] "Communication Received from the United Kingdom of Great Britain and Northern Ireland Concerning its Policies Regarding the Management of Plutonium," INFCIRC/549/Add.8/12, www.iaea.org, 15 September 2009.
[41] Martin Forwood, "The Legacy of Reprocessing in the United Kingdom," International Panel on Fissile Materials, www.fissilematerials.org, July 2008.
[42] "Historical Accounting for UK Defence Highly Enriched Uranium," Ministry of Defence, www.mod.gov.uk, March 2006.
[43] "Communication Received from the United Kingdom of Great Britain and Northern Ireland Concerning its Policies Regarding the Management of Plutonium," INFCIRC/549/Add.8/12, www.iaea.org, 15 September 2009.