MOX in Japan: Ambitious Plans Derailed

Hina Acharya

This chapter assesses Japan’s ambitious but so far largely derailed plans to use substantial amounts of mixed-oxide (MOX) plutonium-uranium fuel in light water nuclear reactors (LWRs). Field interviews were conducted in Japan in 2018 with policymakers, power companies, scholars, and NGOs. The report explores the economics, security, safety, performance, and public acceptance of the MOX program. Japan had planned to commence commercial MOX use in 1997, but numerous scandals delayed the start by a dozen years until 2009. The program paused again in 2011 due to the Fukushima nuclear accident, and then restarted slowly in 2016. To date, the MOX program has consumed only about five percent of the 50 tonnes of nuclear weapons-usable plutonium separated from Japanese spent fuel, while the rest is stockpiled in Europe and Japan, raising significant concerns for East Asian regional security. Japan’s MOX fuel has also proved to be significantly more expensive than traditional low-enriched uranium (LEU) fuel. Despite such concerns, the Japanese government still envisions MOX as part of its long-term energy plan. This study recommends that Japan increase interim dry cask storage of spent nuclear fuel and delay domestic reprocessing until at least it proves that the MOX program can effectively consume the existing plutonium stockpile.