For those of you unfamiliar with nuclear power, ever since President Carter, all spent nuclear fuel rods are locked away until they decay to the point where they're no longer radioactive (which can be a hella long time). However, these rods aren't completely used up. They can be recycled and have more useful energy extracted. The reason why Carter did not support nuclear recycling is because the recycling process creates small amounts of high quality plutonium which could be the basis of a nuclear warhead and Carter wanted to stop or reverse nuclear proliferation.

http://www.washingtonpost.com/wp-dyn...012502229.html