Adequate supplies of electricity have allowed Japan to make impressive economic advances. But Japan can sustain these advances only with assured supplies of fuel. To this end, it diversifies both its type of power producing facilities and its sources of fuel. Nuclear power provides Japan 30% of its electricity today and by the end of the century it will grow to 40%. Japan is facing both an opportunity and a dilemma. Japan's opportunity to convert its nuclear power from the conventional uranium based fuel to the more expensive mix of plutonium and uranium fuel extends its fuel supply by up to ten years at a substantial dollar cost as well as a potential nuclear weapons proliferation cost. This study estimates that if Japan elects to fuel its reactors with mixed plutonium and uranium oxide the dollar cost alone would run from $135 million to $800 million per year over the conventional uranium fuel. This cost is compounded by the fact that plutonium - unlike reactor grade uranium - is weapons usable. Plutonium in the hands of Japan may attract other countries to also want plutonium. This study concludes that one means of assuring energy and minimizing the potential for weapons proliferation is to develop an international nuclear fuel bank that could supply countries with energy credits.