link:http://news.yahoo.com/2-british-ships-arrive-japan-carry-plutonium-us-015323402.html
"Two British ships arrived in eastern Japan on Monday to transport a shipment of plutonium — enough to make dozens of atomic bombs — to the U.S. for storage under a bilateral agreement.
[...]
Japan has accumulated a massive stockpile of plutonium — 11 metric tons in Japan and another 36 tons that have been reprocessed in Britain and France and are waiting to be returned to Japan — enough to make nearly 6,000 atomic bombs.
[...]
The Pacific Egret and Pacific Heron, both operated by Pacific Nuclear Transport Ltd., will take the 331 kilograms (730 pounds) of plutonium to the Savannah River Site, a U.S. government facility in South Carolina under a pledge made by Japan in 2014. The plutonium, mostly from the U.S. and some from France originally, had been used for research purposes."