Why are we still talking about proliferation? Proliferation has already happened: Pakistan has the bomb, North Korea has the bomb, Iran is probably building one. We were only ever going to delay the inevitable, once you prove that it can be done, it's only a matter of time before technology brings the price of doing it down to a level that less wealthy nations can afford. There may be other reasons why we shouldn't reprocess fuel, but proliferation isn't one of them.