Japan's plutonium stocks largely consist of so-called reactor-grade plutonium. For years Japanese government and nuclear industry officials have claimed that reactor-grade plutonium is not suitable for nuclear weapons. This despite the fact that the United States conducted a nuclear weapons test with such material forty years ago and even provided classified data to Japan in the 1970s to prove that it was possible to make nuclear weapons. That was done in a failed effort by the Carter Administration to stop Japan's "commercial" plutonium program. In fact, Japan could make highly sophisticated nuclear weapons with its stocks of plutonium, including that contained in MOX fuel.(2)
That's interesting - maybe this has a lot to do with why no one seems to care that Iran is supposedly aiming for energy production rather than weapons grade... Given the right techniques apparently that could be irreverent. And funnely enough it will be US research that helped.



