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1958 US-UK Mutual Defence Agreement
From Wikipedia, the free encyclopedia
The 1958 US-UK Mutual Defence Agreement is a bilateral treaty between the United States and the United Kingdom on nuclear weapons cooperation.
It was signed after the UK successfully tested its first hydrogen bomb during Operation Grapple. Whilst the US has nuclear cooperation agreements with other countries, including France and some NATO countries (see nuclear sharing), this agreement is by far the most comprehensive.
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The agreement enables the US and the UK to exchange classified information with the objective of improving each party's "atomic weapon design, development, and fabrication capability". This includes development of defence plans; training personnel in the use and defence against nuclear weapons; evaluation of enemy capabilities; development of nuclear delivery systems; and research, development and design of military reactors. The agreement also provides for the transfer of special nuclear material (e.g. plutonium, highly enriched uranium, tritium), components, and equipment between the two countries, and the transfer of "non-nuclear parts of atomic weapons" to the UK.
The agreement also covered the export of one complete US submarine nuclear propulsion plant and its enriched uranium fuel which was installed in the UK's first nuclear powered submarine, HMS Dreadnought.
The UK was able to carry out underground nuclear tests at the US Nevada Test Site, the first taking place on 1 March 1962, following this agreement.[1]
There are also confidential intelligence matters covered by the agreement. The UK government has not published these sections "because of the necessity for great confidentiality and because ... it might well assist proliferation".[2]
This agreement replaced the earlier "Agreement for Cooperation Regarding Atomic Information for Mutual Defense Purposes" of 1955. A separate Polaris Sales Agreement was signed on April 6, 1963.
An early benefit of the agreement was to allow the UK to "Anglicise" the US W28 nuclear warhead as the Red Snow thermonuclear weapon for the Blue Steel missile by 1961.[3]
The U.S. President authorised the transfer of nuclear warhead components to the UK between at least the years 1975 to 1996.[4][5]
There is evidence that the warhead design of the British Trident system is similar to, or even based on, the US W76 warhead fitted in some US Navy Trident missiles, with design and blast model data supplied to the UK.[6][7]
Under the agreement 5.37 tonnes of UK produced plutonium was sent to the USA in return for 6.7kg of tritium and 7.5 tonnes of highly enriched uranium over the period 1960-1979. A further 0.47 tonne of plutonium was swapped between the UK and US for reasons that remain classified.[8] Some of the UK produced plutonium was used in 1962 by the USA for the only known nuclear weapon test of reactor-grade plutonium .[9]
The plutonium sent to the USA included some produced in UK civil Magnox reactors, and the USA gave assurances that this civil plutonium was not used in the US nuclear weapons programme. It was used in civil programmes which included californium production and reactor research. However the UK did obtain military nuclear material in return, so via this barter UK civil power stations probably provided weapons material.
Due to the fact that the UK relies heavily on US assistance to maintain and develop its nuclear arsenal, this has raised questions about whether this level of cooperation is in breach of the Nuclear Non-Proliferation Treaty. Despite this, in 2004 negotiations were completed to extend the treaty for 10 years to 2014.[10]
- Atomic Weapons Establishment
- Nuclear weapons and the United Kingdom
- Nuclear weapons and the United States
- Quebec Agreement
- Special relationship
- ^ UK Mounts First Underground Nuclear Test (UGT). Atomic Weapons Establishment. Retrieved on 2007-03-15.
- ^ UK-US Mutual Defence Agreement. Lords Hansard - column 1119. Hansard (22 Jun 2004). Retrieved on 2007-03-15.
- ^ Yellow Sun MK.2 Enters Service. Atomic Weapons Establishment. Retrieved on 2007-03-15.
- ^ National Security Decision Memorandum 276. U.S. National Security Council (October 15, 1974). Retrieved on 2007-03-15.
- ^ National Security Directive 61. The White House (July 2, 1991). Retrieved on 2007-03-15.
- ^ Britain's Next Nuclear Era. Federation of American Scientists (December 7, 2006). Retrieved on 2007-03-15.
- ^ Stockpile Stewardship Plan: Second Annual Update (FY 1999). U.S. Department of Energy (April 1998). Retrieved on 2007-03-15.
- ^ Plutonium and Aldermaston - an historical account. UK Ministry of Defence (4 September 2001). Retrieved on 2007-03-15.
- ^ Additional Information Concerning Underground Nuclear Weapon Test of Reactor-Grade Plutonium. U.S. Department of Energy (June 1994). Retrieved on 2007-03-15.
- ^ Amendment to the 1958 US-UK Mutual Defence Agreement (on nuclear weapons' cooperation). British American Security Information Council (June 2004). Retrieved on 2007-03-15.
