The breakdown shows about 8.6 tons stored in Japan and about 35.8 tons stored abroad—approximately 21.7 tons in the United Kingdom and about 14.1 tons in France. This represents a slight decrease from the total of about 44.5 tons at the end of 2023, marking the fourth consecutive year of decline.
The plutonium stored overseas refers to material sent to the UK and France for reprocessing under contract that has yet to be returned to Japan. In principle, such plutonium is fabricated overseas into MOX fuel and then used in domestic nuclear power plants.
In an effort to enhance transparency in plutonium use and gain both domestic and international understanding, the Japanese government annually publishes, and submits to the International Atomic Energy Agency (IAEA), the status of management of unirradiated separated plutonium held in Japan and abroad in accordance with the IAEA Guidelines for the Management of Plutonium. This practice has been in place since 1994.
According to the JAEC, the main reasons why Japan’s plutonium stockpile did not decrease further in 2024 were that no reprocessing of spent fuel entrusted to the UK and France was carried out—thus no plutonium was recovered—and that no new MOX fuel was loaded during the year at Kansai Electric Power’s Takahama-3 and -4 (PWRs, 870 MWe each) and Shikoku Electric Power’s Ikata-3 (PWR, 890 MWe), all of which have a track record of using MOX fuel.
