The Thermal Oxide Reprocessing Plant (Thorp), which has cost pounds 2.8bn to build, will reprocess spent fuel from British and foreign nuclear reactors. But it could cost the industry an additional pounds 3bn to dispose of the plutonium produced by this process, informed estimates say.
This would be in addition to the pounds 18bn needed to knock down old nuclear plant, highlighted in a National Audit Office report published last week. And while the industry is putting some money aside to deal with decommissioning old power stations, no provision has been made for the disposal of plutonium.
The industry would have to build a second deep underground repository at least as large as the one that its waste disposal company, UK Nirex, already plans to excavate near Sellafield. The safety of the planned repository is already highly controversial, because of evidence that drinking water could be contaminated.
The Government must decide in the next few weeks whether to allow Thorp to operate. When it was first planned in the Seventies, the nuclear generating companies believed that the plutonium produced at Thorp would be a valuable fuel for fast-breeder reactors. However, in the mid- Eighties, such hopes evaporated and instead of a 'plutonium credit' the companies' accounts judged it to be worthless. Now experts warn that it should be regarded as a real cost.
The ultimate fate of Britain's civil plutonium stockpile will figure in the Government's review of the nuclear industry to be held towards the end of this year. The stockpile could, by itself, force the Government to change its policy that Britain should not build fast- breeder reactors. These can consume plutonium, transmuting it into other elements which, while highly radioactive, present fewer disposal problems.
By the early years of the next century, some 80 tonnes of British plutonium - with a half-life of 24,000 years - will have accumulated at Sellafield. The industry says it should be stored there until some use can be found for it.
Dr Peter Wilmer, head of the fuel cycle division of Nuclear Electric, says: 'We have not given any thought to regarding plutonium as waste material.' It could be recycled into pressurised-water reactors (PWRs) as 'Mox' (mixed plutonium and uranium oxide fuel) or used as fuel in fast-breeder reactors.
But the Government has scrapped the fast-breeder reactor programme. Next year it will close the prototype fast reactor at Dounreay, the only one in Britain able to consume, rather than generate, plutonium. Britain has also withdrawn from a European plan to build an international fast- breeder reactor.
Dr Wilmer says it would not be economic to convert Britain's existing advanced gas-cooled reactors to use the plutonium. A special plant would have to be built to make 'Mox'. AGRs at present run on uranium fuel, which is currently cheap and poses fewer problems with radiation emissions, so there is no financial incentive for such a switch.
British Nuclear Fuels has a Mox fabrication plant ready to come on stream, capable of manufacturing about eight tonnes of PWR fuel (containing at most 0.65 tonnes of plutonium) and hopes to obtain planning permission for a plant producing 100 tonnes a year. However, this is expected to use plutonium recovered for foreign customers.
In addition, recycling plutonium into PWRs will not significantly decrease the stockpile because the process ultimately produces more of it. The problem is postponed, not solved.
Nor does Nuclear Electric, plan to recycle plutonium into the new Sizewell PWR. Using Mox fuel would be an unnecessary complication as staff get used to unfamiliar PWR technology.
Russia is considering getting rid of surplus military plutonium by 'un-reprocessing' it - mixing it back with radioactive material from the spent nuclear fuel from which it was originally reprocessed. Separated plutonium cannot be buried directly in an underground repository - it has to be diluted, to prevent an accidental nuclear reaction, and be 'spiked', possibly with other radioactive material, to prevent terrorists, or others, mining it as a ready source of explosive nuclear material. Both these processes would increase the bulk of material and thus the cost of disposal.
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