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Britain should consider stopping producing plutonium and urgently consider ways of dealing with its existing stockpile of the material, including burning it in a fast reactor, the IMechE has said.
In a policy statement on the 112-tonne stockpile, the institution said that maintaining it cost the taxpayer £80 million a year. The institution warned that the material could be used in the proliferation of nuclear weapons.
Plutonium was originally produced as part of the nuclear weapons programme. It was also thought that the material could be stored and used as fuel for a new generation of fast-breeder reactors, but this never came to pass.
Now the IMechE says the government should take steps to assess the materials in the stockpile, which are likely to be of widely differing quality, convert some to mixed-oxide fuel (Mox) for nuclear reactors, and burn the rest in a commercially viable fast reactor such as GE-Hitachi’s Prism system.
Of the 112-tonne plutonium stockpile, 28 tonnes is foreign-owned. It is largely stored at Sellafield, with the rest at Dounreay. “We would like the government to explore using a Prism reactor in the UK to process some of that lower-grade plutonium,” said Tim Fox, head of energy and environment at the IMechE. “The stuff that can’t be used in that could be turned into Mox. We could generate 600MW based on two of these reactors, so they would generate some useful electricity.”
Many of the engineering challenges in building fast reactors had been overcome, Fox said. There was a limited market globally for Mox fuel but converting spent fuel into Mox at least made it difficult to access the plutonium, he said. A failed Mox plant at Sellafield had been over-engineered, but a simpler system could create fuel for reactors able to run on the mixed-oxide alternative, Fox said.
Britain is currently producing 4-6 tonnes of plutonium every year. A country such as France, which generates most of its electricity from nuclear power, recycles its plutonium as Mox, so reactors are kept supplied. “There is a benefit from a security point of view as it is very difficult to get plutonium out of Mox,” Fox said.
Plans would need to be put in place to enable new or existing reactors in the UK to burn Mox fuel. Using it in a reactor such as Sizewell B would mean taking a hit on efficiency compared with uranium fuel, of which there are plentiful supplies at present.
“We have to question why we are producing plutonium when there are inadequate plans for dealing with the stockpile,” Fox said. “Burning plutonium in a fast reactor such as Prism turns it into waste rather than it being a material that could be taken and used in a nuclear weapons programme. About 10% of the stockpile is probably unusable and should find home in a geological repository.
“It doesn’t make any sense to keep producing material and it doesn’t make any sense to keep producing it for Mox when the market for Mox is very limited.
“If we had many more nuclear power stations that could use Mox it would make more sense. But that’s hypothetical at the moment, and it won’t happen until the 2030s.”