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. This has caused a few major media news outlets to express an unjustified concern that recovered plutonium in reprocessing could be captured by terrorists for use in a nuclear weapon. But that plutonium is not weapons grade.
A major purpose for reprocessing, as France does at La Hague, is to reuse the very valuable plutonium 239(Pu 239) and recycle the uranium, thus extending the world’s nuclear fuel supplies. The other important purpose is to greatly reduce the radioactive spent fuel storage requirement. Only the radioactive 5% 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 process.
All commercial nuclear reactors produce fissionable Pu 239 from non-fissionable U 238, and that Pu 239 is burned as part of the fuel. After five years the spent fuel capsules contain some fissionable U 235 and 1 percent reactor grade Pu 239, just not enough to sustain the reaction. But during those five years of operation, several plutonium isotopes like Pu 238, 240, 241, and 242 build up in the plutonium. These essentially prevent its use in a nuclear weapon, but it is still reactor grade, usable as power plant fuel.
A major purpose for reprocessing, as France does at La Hague, is to reuse the 1 percent Pu 239 and recycle the uranium. The other purpose is to greatly reduce the radioactive spent fuel storage requirement by recycling 95% of the fuel capsules.
The spent fuel capsule is 2 percent plutonium/uranium fuel; 93 percent uranium 238 and about 5 percent dangerous fission products. It’s just that 5 percent which 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 U.S. has a growing 60,000 tons of radioactive spent fuel racks in storage pools and storage casks waiting for the now cancelled 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 isotopes, producing 60-70 percent Pu 239, not the 90 percent+ needed for a bomb.
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.
Rolf Westgard is a member American Nuclear Society and guest faculty of energy subjects for the University of Minnesota Lifelong Learning program. He taught the fall quarter class #15037 — Future of Fukushima and Iran’s nuclear program.