Nuclear Chemistry
Recycling Spent Reactor Fuel
Dr. Frank Settle


Spent fuel from nuclear reactors contains considerable amounts of U-235 and Pu-239. After 3 years in a reactor, 1,000 lbs. of 3.3-percent-enriched uranium (967 lbs. U-238 and 33 lbs. U-235) contain 8 lbs. of U-235 and 8.9 lbs. of plutonium isotopes along with 943 lbs. of U-238 and assorted fission products. Separating the U-235 and Pu-239 from the other components of spent fuel significantly addresses two major concerns. It greatly reduces the long-lived radioactivity of the residue and it allows purified U-235 and Pu-239 to be used as reactor fuel. (Courtesy of the Uranium Information Center)

Two options are available for cooled spent fuel rods; they can be moved to a more permanent site for storage or they can be reprocessed to remove the uranium and plutonium. In either case, these fuel rods must cool in storage ponds near the reactor for several months in order to reduce their short-lived radioactivity and to allow them to dissipate their initial high thermal energy. Reprocessing involves chopping up the fuel rods and dissolving the pieces. The plutonium and uranium are then removed by chemical separation. The United States used a plutonium-uranium extraction (PUREX) process to for this separation.

The transuranic elements and fission products can be encapsulated in glass and disposed as waste. Gaseous diffusion or other processes can be used to enrich the uranium. The plutonium can be mixed with enriched uranium to make mixed oxide (MOX) reactor fuel. Purified plutonium can also be used for nuclear weapons. Great Britain and France have built large reprocessing plants to produce MOX fuel. They reprocess spent fuel not only from reactors in their respective countries, but also from reactors in other nations.

In the United States, no spent fuel from nuclear power plants is reprocessed. It is currently stored at locations near the approximately 70 plants throughout the country. These plants produce a total of approximately 500 tons of waste per day. Recently, the Department of Energy opened the Waste Isolation Pilot Plant (WIPP) facility in Carlsbad, New Mexico, for the permanent storage of transuranic wastes. If all goes well, the Yucca Mountain facility in Nevada will become the permanent storage location for high-level waste from civilian power reactors and defense-related activities.

(Courtesy of the Department of Energy)

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Principal Investigator Laurence Peterson
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