TOKYO, Mar 18: Japan will return Some 331 kilogrammes (730 pounds) of plutonium , enough to produce 50 nuclear bombs, to the United States starting this weekend as part of a bilateral storage deal, Greenpeace and other anti-nuclear campaigners said Friday. The stockpile, provided by the US, Britain and France decades ago for research purposes, has caused disquiet among anti-nuclear groups and neighbouring countries given Japan has the know-how to produce a nuclear weapon -- even as it adamantly chooses not to.     ?AFP