Nuclear reprocessing

Eventually, the fuel in a nuclear reactor becomes spent, and, rather than being disposed of, it is reprocessed. This both recovers uranium and separates from the fission products. Short-lived radioactive products are initially allowed to decay while the spent fuel is retained in pond storage. After this period, the uranium is converted into the soluble salt [U02][N03)2 (see Box 7.3). In the series of reactions 3.18 3.21, the nitrate is converted into UF.  

At this stage, the UF contains both and Apphca-tion of Graham s law of effusion  

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Special safety constraints apply to equipment selection, design, and operation in nuclear reprocessing (269). Equipment should be reHable and capable of remote control and operation for long periods with minimal maintenance. Pulsed columns and remotely operated mixer—settlers are commonly used (270). The control of criticaHty and extensive monitoring of contamination levels must be included in the process design. 

Hanson, C. et al., Proc. Int. Solvent Extr. Conf. (Liege), 1980, 2, paper 80-70 The solvent ( Butex ), an extractant in nuclear reprocessing may decompose violently in contact with nitric acid. Hydrolysis to butanol, followed by violent oxidation, catalysed by nitrous acid, is involved. 

Today, the most important environmentally damaging anthropogenic radiation comes from atmospheric testing of nuclear weapons conducted 20 to 30 years ago, authorized discharges to the sea from nuclear reprocessing plants, and from the Chernobyl accident in 1986 (Aarkrog 1990). 

Chromox [Chromium oxidation] A process for destroying organic pollutants in aqueous wastes by oxidation with hydrogen peroxide, catalyzed by Cr6+. Developed by British Nuclear Fuels in 1995, originally for use in nuclear reprocessing. 

Proceedings of the International Conference on Nuclear Reprocessing, RECORD 87 Soc. Francaise d Energie Nucleaire Paris, Vol. 1, 1987. 

Johnes, S. R., Fulkner, M. J., McKeever, J. Stewert, T. H. 1991. Aspects on population exposure consequent on discharges of radionuclides to the environment from the nuclear reprocessing plant at Sellafield at Cumbria. Radiation Protection Dosimetry, 36, 199-204. 

Tahraqui, A., Morris, J.H. 1995. Decomposition of solvent extraction media during nuclear reprocessing Literature review. Sep. Sci. Technol. 30 (13) 2603-2630. 

Although best known as a tool and hazard in actinide separation for nuclear reprocessing, the mix is evaluated as a Sprengel explosive. 

Radioactive substances The principal sources of radionuclides released into the environment include nuclear weapon testing fallout from accidents such as the Chernobyl accident in 1986 or from foundering of nuclear submarines from the dumping of nuclear waste into the deep ocean and from discharges from nuclear power plants and nuclear reprocessing plants. 

Given the importance of the oxidation states of the actinides in reprocessing and the capability of heterogeneous semiconductor photocatalysts to manipulate the valence states of a wide range of metal ions, attention has been given to the potential applications of photocatalysis in nuclear reprocessing scenarios [59-65]. The attractions of this are twofold, and lead to a further minimisation of the environmental impact associated with fuel use and processing ... 

Upon removal of illumination, the concentration of photogenerated U(IV) in the TBP phase was found to be invariant with time, indicating that, as in the aqueous phase photocatalysed reductions of Ce(IV) to Ce(III) and U(VI) to U(IV), the photocatalysed reduction of U(VI) to U(IV) in the non-aqueous TBP phase can be rendered permanent on timescales appropriate for nuclear reprocessing. 

AVH [Atelier de Vitrification de la Hague] A process for immobilizing nuclear waste, operated at La Hague, France, based on the earlier AVM process. Used also in the THORP nuclear reprocessing plant at Sellafield, UK. 

PYRO-A A pyrochemical process proposed for use in nuclear reprocessing for separating transuranic elements from fission products, once the uranium has been removed by the UREX process. The spent fuel is dissolved in a molten salt bath and electrolyzed. The transuranic elements deposit on the cathode, and the fission products remain in the melt. Developed by the Argonne National Laboratory. See also PYRO-B. 

NOj reduction H mordenite Effluent clean-up in nitric acid and nuclear reprocessing plants... 

Nuclear weapons testing was deliberate however many other releases of radionuclides are accidental. These have included fires and spillages at nuclear reprocessing plants resulting in releases of an assortment of nuclides to the atmosphere and the oceans, including super-heavy elements from the actinide group of the Periodic Table (Fig. 2.2) such as plutonium (Pu). Similarly, accidental sinking of nuclear submarines has released radionuclides to the bottom waters of the... 

Sources and Amounts of Plutonium in the Environment. Since 1945 approximately 3300 kg of plutonium has been injected into the environment, mostly (>90Z) from atmospheric explosions of nuclear weapons. This corresponds to about 380 kCi total alpha radioactivity. The addition to this amount by releases from nuclear power operations is much smaller the major continuing addition is ca. 0.1 kCi per month released to the Irish Sea from the British nuclear reprocessing plant at Windscale. About 2/3 of the plutonium from nuclear explosions would be formed into highfired oxides which would be rather inert chemically. However, the remainder, created during the explosion as single atoms via the U(n, J ) U(28 ) Pu... 

Schuller, W., et al. Nuclear Reprocessing and Waste Treatment at Karlsruhe Nuclear Research Center, Proceedings of Nuclear Power and Its Fuel Cycle, vol. 3, International Atomic Energy Agency, Vietma, 1977, p. 579. 

Idaho US/1972-1974 Deer 6500-79000 Nuclear reprocessing Markham etal., (1983)... 

Japan/1979-1983 Pine needle <700 - 1.8 X 10 Nuclear reprocessing Muramatsu and Ohmomo (1986)... 

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