Nuclear energy is the only source of electricity that comprehensively takes responsibility for its associated waste. The nuclear fuel cycle, from the power plant forward, is designed to continually shield, and isolate, used fuel from the ambient environment. This characteristic separates nuclear from all fossil, and even renewable, energy resources. Virtually every industrial activity in an advanced civilization creates potentially toxic substances. This includes non-combustion renewable energy, such as wind and solar. We can, and should, responsibly manage all such residues.
Used nuclear fuel is first stored in a pool of water to allow the fastest decaying isotopes including many of the heat-generating byproducts, to decay and cool down.
While used fuel is in storage, radiation is attenuated to very low levels by a few inches of barrier, be it water, steel, or concrete. When used fuel has decayed to about 75% to 85% of its original level, it is moved from pools into dry casks.
Casks are inspected and tested in accordance with stringent federal Nuclear Regulatory Commission (“NRC”) regulations to assure they consistently contain radiation. Spent fuel containers of the same general type used in Wisconsin and throughout the U.S. were present at the Fukushima tsunami site, and came through unscathed. The casks will easily last for 100 years and probably much longer. A NRC Environmental Impact Statement recently concluded that used nuclear fuel can be safely managed in dry casks indefinitely.'
Although there may well be better uses for used nuclear fuel (please see the Q & A on what “advanced nuclear” means), the consensus of scientists who have studied the question is that, if we choose to treat spent fuel as a “waste” instead of a resource, it can be isolated from the biosphere by putting it into the earth’s crust in zones that have been stable and dry for millions of years, and will be stable and dry for millions more. Such disposal is already being pursued across the world.
Scientifically, it is reasonable to be confident about this kind of disposal because natural nuclear reactors operated on earth for hundreds of thousands of years while life was evolving, and the associated byproducts, although they developed in a water saturated zone, have moved only about 10 feet in the ensuing billion + years.