Japanese plutonium stockpile

Although popular opinion is against the development of atomic weapons, Japan probably has the technical knowledge to be able to build nuclear weapons within months if needed. This makes Japan a virtual nuclear power.

Japan is the non-nuclear state with the largest stockpile of plutonium: 47 tonnes. 37 t are in French and UK nuclear reprocessing plants, and 10 t are in Japan. Japan’s nuclear industry believes in the nuclear fuel life cycle. It has tried for decades to recycle depleted fuel rods. The resulting plutonium would be used in a fast-breeder reactor.

The Monju plant for this purpose was closed in 2016, after numerous incidents. Only 4 of the 9 commercial reactors are set up to use the MOX rods which contain Pu. This is not enough to reduce the Pu mountain. When the reprocessing plant in Rokkasho begins operation in 2021, Pu will accumulate rather than decrease.