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More than 100 members of Britain's Parliament last week signed a motion criticizing the government for failing to develop a policy for managing plutonium removed from dismantled nuclear weapons. The MPs also opposed the decision to convert part of the plutonium stockpile into mixed oxide fuel (MOX) for nuclear power reactors.

The MPs want to halt plans to build a £500-million (US$800-million) MOX recycling plant until a review of policy has been completed. Their public statement coincides with the publication of the report of a two-year study, coordinated by the Citizens' Nuclear Information Center in Tokyo and the World Information Service on Energy in Paris, which concludes that recycling MOX could lead to plutonium proliferation.

MOX is made by mixing oxides of uranium with small quantities (5-10 per cent) of oxides from weapons-grade plutonium. Some countries, including Britain, France, Germany and Japan, are considering the manufacture of MOX as a way of reducing plutonium stockpiles. They also believe it to be a useful alternative to fossil fuels.

The authors of the international MOX assessment study argue that such a strategy could be counterproductive. They contend that it will keep plutonium in circulation for longer than necessary, increasing the risk of its misuse by terrorists. They also point out that the quantity of plutonium in the MOX mixture is too small to make a dent in the stockpiles. France has over 40 tonnes of plutonium stockpiled, and Britain over 50 tonnes.

The study also raises questions about security at plutonium stores, claiming that site operators, particularly in Britain, lack the capability to trace material that is stolen or illegally diverted to weapons making.

Site operators aim to keep ‘unaccounted-for material’ to below 8 kg, the minimum quantity estimated by the International Atomic Energy Agency to be needed to make a nuclear device. But the MOX study claims that the Thermal Oxide Reprocessing Plant operated by British Nuclear Fuels at Sellafield in northwest England cannot detect missing plutonium unless the material weighs more than 220 kg.

The study claims that a minimum weekly inventory of plutonium stocks is needed to detect stolen or diverted material quickly “instead of every year as practised today”.

But such claims are rejected by Peter Metcalfe of British Nuclear Fuels. “The plutonium is subject to very strict checks and safeguards by multinational teams of inspectors to ensure that it is safely handled and accounted for,” he says.