Japan's stockpile of plutonium extracted and separated from spent nuclear fuel increased to 43.1 tons as of the end of 2004, up 2.5 tons from the previous year, the government reported to the Atomic Energy Commission on Tuesday.
Most of the increase was from reprocessing of spent nuclear fuel, conducted in Britain. Of the total amount, 37.4 tons were stored overseas.
The government plans to use the reprocessed plutonium to produce plutonium-uranium mixed oxide fuel for use in plutonium-thermal nuclear power plants in the future.