The amount of energy utilised from the nuclear fuel in a standard nuclear reactor remains only a few percent of the total energy available, and nuclear fuel can be recycled and reused to acquire more of this energy. The US currently recycles none of its nuclear waste material, but could run its electricity grid for 100 years by recycling its own nuclear waste, not to mention also cutting the half-life of the recycled waste to hundreds of years, as opposed to millions. Nuclear recycling plants and special breeder reactors can effectively harness much more of the energy available in nuclear material, including from decommissioned nuclear weapons, however they remain expense and present new safety concerns.
"Light water reactors" are the most common type of thermal-neutron reactor, themselves the most common nuclear reactor design, however there have been others in the history of nuclear energy that may be more beneficial. Light water reactors became favoured over other types with the discovery of vast amounts of nuclear fuels, however "breeder reactors" that generate more fissile material than it consumes were favoured in the early days of nuclear reactor experimentation. In theory, such reactors could extract almost all of the energy contained in uranium or thorium, decreasing the amount of fuel needed by 100 times, when compared to widely used once-through light water reactors.
However the current picture is far from ideal, during the operation of the most common reactors substances build up on the nuclear fuel over time, absorbing so many neutrons from the nuclear reaction that the reaction stops. At this point fresh fuel is needed, in the US the old used fuel is stored, while in Russia, the UK, France, Japan and India, this fuel is reused by reprocessing to remove the neutron absorbing products of the used fuel. There are so many prospects in nuclear power generation that have not been fully investigated, or are not in use worldwide, due to the massive initial cost of building and maintaining nuclear reactors. But the future of humanity's energy needs and the end of nuclear weapons could coincide, with the more intelligent reuse of nuclear material and investment in a diverse range of nuclear reactors.