days after discharge, less than 2 percent of the activity is from actinides, but after 10 years of cooling, the actinides produce almost 20 percent of the activity.


Alpha-Active Wastes82 Throughout the nuclear industry, uranium is converted from one chemical form to another: from uranium oxide to uranium hexafluoride for enrichment, from uranium hexafluoride to uranium dioxide for fuel-material preparation, and so on. There are radioactive wastes from these processes. They are not as radioactive as mill tailings, and ought probably to be mingled with them for disposal,* but institutional arrangements have not been made for this step.

Laboratory operations involving plutonium, 233U, and other actinides also produce wastes that contain long-lived alpha activity. In the past, the concentration of alpha activity governed the method of disposal: Low concentrations were considered low-level wastes, to be buried or dispersed. However, the increased concentrations and quantities of this material being disposed of, and public fear of the consequences of its dispersal, stimulated a change in policy, and this material is now considered in the same disposal category as high-level waste.

Looking to the future, we can expect to see a large increase in the generation of alpha-active waste if 233U and plutonium are recycled. A considerable amount of waste is generated during nuclear fuel fabrication: dusts from grinding operations, contaminated fabrics from filters, contaminated crucibles and tools, contaminated metal pieces from rejected fuel elements, and so on. (For a given number of atoms, radioactivity is inversely proportional to half-life, and the half-lives of possible contaminants are 700 million years for 235U, 160,000 years for 233U, 23,000 years for 239Pu, and 6500 years for 240Pu.)

A further consideration in recycled fuel is the contamination introduced by other actinide nuclides. These materials (232U, 238Pu, 241Pu, americium-241 (241Am), and others) have even shorter half-lives and higher activities than those just mentioned, and for that reason, they have been suggested as radioactive “spikes” to safeguard nuclear fuel, discussed in this chapter under “Safeguarding the Domestic Fuel Cycle.”


Reprocessing Wastes from Military Production Although not within the responsibility of a civilian industry, military production wastes are the major focus of current concerns about waste management. The important wastes are the aqueous raffinates from reprocessing of fuel to recover plutonium for weapons. Three different processes have been used in the

*

Statement 5–31, by J.P.Holdren: No presently agreed-to plan for managing tailings justifies either the term “disposal” or the addition of other wastes to the piles.



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