Plutonium processing solid, oxidizers

A variety of methods have been used to characterize the solubility-limiting radionuclide solids and the nature of sorbed species at the solid/water interface in experimental studies. Electron microscopy and standard X-ray diffraction techniques can be used to identify some of the solids from precipitation experiments. X-ray absorption spectroscopy (XAS) can be used to obtain structural information on solids and is particularly useful for investigating noncrystalline and polymeric actinide compounds that cannot be characterized by X-ray diffraction analysis (Silva and Nitsche, 1995). X-ray absorption near edge spectroscopy (XANES) can provide information about the oxidation state and local structure of actinides in solution, solids, or at the solution/ solid interface. For example, Bertsch et al. (1994) used this technique to investigate uranium speciation in soils and sediments at uranium processing facilities. Many of the surface spectroscopic techniques have been reviewed recently by Bertsch and Hunter (2001) and Brown et al. (1999). Specihc recent applications of the spectroscopic techniques to radionuclides are described by Runde et al. (2002b). Rai and co-workers have carried out a number of experimental studies of the solubility and speciation of plutonium, neptunium, americium, and uranium that illustrate combinations of various solution and spectroscopic techniques (Rai et al, 1980, 1997, 1998 Felmy et al, 1989, 1990 Xia et al., 2001). 

At the tail end of a solvent extraction process, the solvents are separated from the solutes for recycle. In this application of solvent extraction, vacuum distillation is used to separate volatile zinc and magnesium from coprocessed uranium and plutonium and from the uranium product. Feed to vacuum distillation is solid alloy. Overhead and bottom products are likwise cast into a solid alloy. These vacuum distillation operations are conducted in separate cells. The actinide products are converted to oxide for fuel fabrication. 

The important chemical transformation process in surface water is the oxidation or reduction of plutonium. In waters with low suspended solids, plutonium is generally found in oxidized forms, dissolved in the water. In waters with high suspended solids, plutonium is generally reduced and sorbed onto either suspended solids or sediments (Choppin and Morse 1987 Higgo and Rees 1986 Nelson etal. 1987). 

HNA was incorporated into many nuclear fuel reprocessing plants in the early 1970s replacing the ferrous sulfamate and hydroxylamine sulfate for plutonium reduction because it possessed the proper Pu(IV) to Pu(III) reduction attributes and the gaseous reaction products N2, N2O, and water contributed to the minimization of the volume of solid wastes produced. The French PUREX process at the La Hague site safely uses a mixture of HNA and nitric acid for the reductive stripping phase of plutonium. The British also used HNA in the thermal oxide reprocessing plant (THORP) for over several years (Barney, 1998). 

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