Reprocessed spent nuclear fuel (SNF) has seen Japanese stocks of plutonium significantly grow over the past year.

From 2.5 tonnes the previous year, plutonium extracted and separated from spent nuclear fuel increased to 43.1t as of the end of 2004, the government reported to the Atomic Energy Commission of Japan. Most of this increase was from reprocessing SNF in the UK and France with 37.4t of the material stored overseas and about 5.7t stored in Japan.

Japan plans to use plutonium to produce MOX fuel.