Of the total, approximately 9.9 tonnes were held in Japan and 34.5 tonnes overseas—around 21.7 tonnes in the United Kingdom and 12.8 tonnes in France. At the end of the previous year, Japan held approximately 8.6 tonnes domestically and 35.8 tonnes overseas. Compared with a year earlier, domestic holdings increased by approximately 1.3 tonnes, while overseas holdings declined by roughly the same amount. The change reflects the shipment to Japan of MOX fuel fabricated using plutonium stored in France for use at Kansai Electric Power Co.’s Takahama Units 3 and 4 (PWRs, 870 MWe each).
Plutonium “held overseas” refers to plutonium recovered from spent nuclear fuel sent to the United Kingdom and France for reprocessing but not yet returned to Japan. In principle, this plutonium is to be fabricated into MOX fuel overseas and used at nuclear power plants in Japan.
Recognising the importance of enhancing transparency in plutonium use and gaining understanding both at home and abroad, the Japanese government has published information annually since 1994 on the management of unirradiated separated plutonium held and used in Japan and overseas, in accordance with the International Atomic Energy Agency’s (IAEA) Guidelines for the Management of Plutonium. The information is also submitted to the IAEA.
In 2025, no additional plutonium was recovered from the reprocessing of spent nuclear fuel entrusted to facilities in the United Kingdom and France. No new MOX fuel was used at nuclear power plants in Japan during the year either. As a result, Japan’s total plutonium holdings at home and abroad remained unchanged from the previous year.
