We believe that your worry about US plans to reprocess nuclear fuel (“Recycling the past” Nature 439, 509–510; 200610.1038/439509b) is misplaced. Since President Carter imposed a reprocessing ban in 1977, it has become clear that other nations' decisions about building nuclear weapons do not depend on what the United States does with its spent fuel.
Furthermore, we consider your claim that “recycling involves separating components that can readily be used to build nuclear weapons” to be misleading on two counts. First, degraded plutonium in spent reactor fuel can only be used in an explosive device with considerable difficulty. Second, although current recycling processes produce pure plutonium that can be used for weapons, the US plan is to perfect a new method called UREX+, which would be configured so as never to separate weapons-quality plutonium.
UREX+ processing is the first step towards consuming excess plutonium in advanced, metal-fuelled fast reactors and reducing the rate at which reactor-grade plutonium is accumulating around the world. Moreover, fast reactors can extract more than 99% of the energy in mined uranium — over a hundred times better than the thermal reactors used today. The combination of recycling and fast reactors also reduces the time that waste needs to be isolated, from thousands of years to a few hundred.
There is still the associated problem that the Nuclear Non-Proliferation Treaty gives all signatories the right to develop a full-scale fuel cycle, and with it the technological infrastructure for making bombs. President Bush has begun to address this, by proposing that the spread of reprocessing technology be curtailed, with waste management and nuclear fuel supplied at reasonable cost—although to be acceptable, such a scheme should be run by an international entity such as the International Energy Agency or the International Atomic Energy Agency.
Properly managed, nuclear power can meet growing energy demand safely, cleanly and indefinitely.