Little noticed in the attention paid to Japan’s nuclear crisis at Fukushima is Japan’s plan to open its long-planned nuclear fuel reprocessing plant at Rokkasho in 2013. Japan would then join France as the world’s only large-scale processors of spent-nuclear-fuel waste from commercial nuclear power plants.
This news has caused some major media news outlets to express the old fears that recovered plutonium in reprocessing could be captured by terrorists for use in a nuclear weapon. But that plutonium is not weapons grade and won’t work in a nuclear bomb.
A major purpose for reprocessing, as France does at La Hague, is to both reuse the very valuable plutonium 239 (Pu 239) fuel and to recycle the uranium, thus extending the world’s nuclear fuel supplies.
Reduce storage requirement
The other important purpose is to greatly reduce the radioactive-spent-fuel storage requirement. Only the radioactive 5 percent fission products in those spent fuel capsules needs to be stored. The other 95 percent can be separated and returned to the new fuel production processes.
All commercial nuclear reactors produce fissionable Pu 239 from non-fissionable U 238 while they are operating. That Pu 239 joins fissionable U235, and both are burned as the reactor’s fuel supply. After five years the spent fuel capsules contain about 1 percent fissionable U 235 and 1 percent reactor grade Pu 239, just not enough in total to sustain the reaction. The racks containing those spent fuel capsules are removed and replaced with fresh fuel.
But during those five years of operation, the produced plutonium builds up other isotopes, like Pu 238, 240, 241, and 242. These essentially prevent its use in a nuclear weapon, but there is still enough of the desirable Pu 239 for that plutonium to be usable as power-plant fuel.
The spent fuel capsule is 2 percent plutonium/uranium fuel; 93 percent uranium 238 and about 5 percent dangerous fission products. It’s only that 5 percent that needs to be safely stored. In France, those fission products are vitrified in glass cylinders, and all of the cylinders from 58 operating reactors are stored in the floors of a few large rooms at La Hague. The United States has a growing 60,000 tons of radioactive spent fuel racks in storage pools and storage casks waiting for the now canceled Yucca Mountain storage facility.
Nuclear weapons programs use specialized plutonium production reactors, which are designed to be turned off frequently. This allows retrieval of the weapons-grade Pu 239 before many of the other isotopes build up. Commercial nuclear reactors do a 4-5 week shut down just once every two years for partial refueling and maintenance. This allows the buildup of multiple plutonium isotopes, producing 60-70 percent Pu 239, not the 90+ percent needed for a bomb.
Constant stopping and starting of commercial nuclear plants is not practical and is easily detected. Commercial nuclear power plants with their 4 percent U 235 and reactor-grade-only plutonium have no role in nuclear weapons programs.
Reprocessing’s benefits
Reprocessing of spent nuclear fuel extends the supply of our uranium resources and reduces the spent-fuel storage requirement. The world’s economically recoverable uranium resource is not all that plentiful, and radioactive-spent-fuel storage is a looming global crisis.
Reprocessing of spent nuclear fuel is the future as we seek to increase energy supply and reduce atmospheric pollution with non-carbon electric power.
Rolf Westgard is a professional member of the Geological Society of America and the American Nuclear Society. He teaches classes on energy for the University of Minnesota’s Lifelong Learning program, including the fall quarter class “Update on Fukushima and the Iran Nuclear Program.”
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