The revelation is bound to embarrass the Government because ministers had led Parliament to believe that reactor-grade plutonium was not suitable for making nuclear explosives, even though the Government has known otherwise for more than three decades.
The US disclosure confirms that reactor-grade plutonium can be used for atom bombs and that Britain was the source of the material used in a successful nuclear test in Nevada in 1962. Ministers are expected to face questions from the Labour MP Llew Smith to explain the inconsistency between British and US accounts.
The 1962 test makes it clear that all plutonium is potentially a nuclear explosive and casts doubt on the robustness of government assertions that British Nuclear Fuels' new Thorp reprocessing plant at Sellafield in Cumbria, which will separate out dozens of tons of plutonium from spent reactor fuel, would not pose any risks of proliferation of nuclear weapons.
Bridget Woodman, of Greenpeace, said: 'This disclosure casts an interesting light on BNFL's attempts to sell reprocessing services to the South Koreans - something which would involve shipping plutonium to the Korean peninsula. BNFL's world-wide trade in the material poses severe threats to international security.'
Yesterday, British Nuclear Fuels confirmed that the plutonium for the Nevada test had come from its Calder Hall and Chapelcross reactors, 'as the US had no suitable material of its own'.
The Government has tried to avoid committing itself on the issue but, on 26 May 1993, when asked to confirm that 'reprocessed plutonium from commercially operated power stations is not suitable for weapons manufacture', the Foreign Office minister Baroness Chalker told the House of Lords on behalf of the Government: 'That is so, to the best of my knowledge'.
Six months earlier Viscount Cranborne also led the Lords to believe that reactor-grade plutonium was unsuitable because 'the usefulness of reprocessed plutonium for weapons purposes depends on its composition'.Reuse content