Fuel transuranium radionuclides

High-level waste thus includes the concentrated wastes that arise from reprocessing of commercial or defense nuclear fuel that contain virtually all the fission products and transuranium radionuclides (except plutonium) in spent fuel. However, the definition does not mention the constituents of the waste, and it is only qualitative because concentrated is not quantified and the minimum fuel burnup that would yield high-level waste is not specified. Although the definition given above referred only to liquid (aqueous) waste, it is clear from further discussions in 10 CFR Part 50, Appendix F (AEC, 1970), that AEC intended that high-level waste also would include concentrated solid waste derived from liquid high-level waste that was suitable for permanent disposal. 

In considering a new definition of high-level waste in accordance with Clause (B) of NWPA, an important issue for NRC was whether this definition should encompass and quantify the traditional, source-based definition in Clause (A). Such a definition would quantify sufficient concentrations of fission products and the minimum concentrations of alpha-emitting transuranium radionuclides in high-level waste from fuel reprocessing. NRC indicated its preference that the definition in Clause (B) should not apply to the primary wastes from fuel reprocessing and that the definition in Clause (A) should continue to apply to all wastes previously considered to be high-level waste in accordance with source-based definitions (NRC, 1987). 

This definition is based on the source of the waste, but certain incidental wastes that arise from fuel reprocessing that contain lower concentrations of fission products and alpha-emitting transuranium radionuclides than the primary reprocessing wastes have been excluded on a case-by-case basis. 

Plutonium is the most important transuranium element. Its two isotopes Pu-238 and Pu-239 have the widest applications among all plutonium isotopes. Plutonium-239 is the fuel for nuclear weapons. The detonation power of 1 kg of plutonium-239 is about 20,000 tons of chemical explosive. The critical mass for its fission is only a few pounds for a solid block depending on the shape of the mass and its proximity to neutron absorbing or reflecting substances. This critical mass is much lower for plutonium in aqueous solution. Also, it is used in nuclear power reactors to generate electricity. The energy output of 1 kg of plutonium is about 22 million kilowatt hours. Plutonium-238 has been used to generate power to run seismic and other lunar surface equipment. It also is used in radionuclide batteries for pacemakers and in various thermoelectric devices. 

Liquid wastes. Historically, the most important radioactive wastes have been liquid wastes that arise from chemical reprocessing of spent nuclear fuel for defense production purposes, i.e., for the purpose of extracting plutonium for use in nuclear weapons. These wastes contain varying concentrations of many radionuclides, primarily fission products and long-lived, alpha-emitting transuranium isotopes. 

The concentrations of the radionuclides originating from both the uranium concentration of the core and defective fuels are measured regularly. Iodine and cesium nuclides are measured by gamma spectroscopy. Occasionally, alpha and beta spec-trometric analyses are performed to determine transuranium and strontium isotopes, respectively. 

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