Tokyo pledged in 1991 that it would adhere to the principle of not retaining surplus plutonium. Since 1994 the Japanese Atomic Energy Commission (JAEC) has published annual inventories of separated plutonium. As of December 1995, the total inventory of separated plutonium managed by Japan was 16.1 tons, with 4.7 tons in Japan and 11.4 tons in Europe. By 2010, the amount of plutonium being stockpiled in Europe will have mounted to 45 tons. A nuclear bomb similar to the one exploded in Nagasaki can be made with seven to eight kg of plutonium.
Japan's nuclear power program based on reprocessed plutonium has aroused widespread suspicion that Japan is secretly planning to develop nuclear weapons. Japan's nuclear technology and ambiguous nuclear inclinations have provided a considerable nuclear potential, becoming a "paranuclear state." Japan would not have material or technological difficulties in making nuclear weapons. Japan has the raw materials, technology, and capital for developing nuclear weapons. Japan could possibly produce functional nuclear weapons in as little as a year's time. On the strength of its nuclear industry, and its stockpile of weapons-useable plutonium, Japan in some respects considers itself, and is treated by others as, as a virtual nuclear weapons state.
http://www.fas.org/nuke/guide/japan/nuke/Plutonium Japan-Bound
AM Archive - Monday, 5 March , 2001 00:00:00
Reporter: Peter Martin
COMPERE: Two shiploads of plutonium, enough to make 20 nuclear weapons, are this morning heading north along the east coast of Australia bound for Japan.
But critics of the voyage within Japan say it isn't necessary, at Peter Martin reports from Tokyo.
PETER MARTIN: One-third of Tokyo is powered by uranium, but none of it by enriched plutonium.
The mixed oxide or mox-plutonium fuel travelling north along Australia's east coast is manufactured in Europe from waste from Japan's nuclear power plants.
http://www.abc.net.au/am/stories/s254680.htm