Through a series of title swaps, some German plutonium has been taken over by the UK's Nuclear Decommissioning Authority (NDA), the authority announced in a statement.
The government said this would not result in any more plutonium being brought into the UK, and instead would bolster the country's security.
It represents four metric tons of the 118 mt of separated plutonium already stored in the UK, mostly at Sellafield.
Platts reports that the deal will make German utilities' plutonium available in France for manufacture into mixed oxide fuel for use in German reactors, and mean that the UK doesn't need to physically transport plutonium owned by the German utilities from Sellafield to France.
The NDA arranged the deal with German utilities and French company Areva.
Charles Hendry, UK energy minister, said: "The agreement reached reduces the need to transport plutonium and the overall amount of plutonium in Europe and therefore improves our security."
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