Dissolution nuclear fuels

Disiloxane, tetramesityl-, 3,206 Disproportionation iridium catalysts, 4,1159 Dissolution nuclear fuels, 6, 927 Distannene, 3,217 Distannoxane, 1,3-dichloro-, 3,207 Distibine, tetraphenyl-, 2,1008 Distibines, 2,1008 Disulfido ligands metal complexes, 2,531-540, 553 bonding, 2, 539 electron transfer, 2, 537 intramolecular redox reactions, 2,537 reactions, 2, 537... 

Uranium. tetrathiocyanatotetrakis[tris-(dimethylamino)phosphine oxide]-structure, 1.87 Uranium carbide nuclear fuels dissolution, 6, 928 Uranium complexes, 3,1131-1215 carbamic acid... 

The rate of dissolution of these reaction products is slow (1.5-2 fig/day per 50-70 mg of solids). Lai and Goya 147) showed that at least 90% of these plutonium aggregates had a diameter <0.01 jum. However, it must be stressed that these forms do not necessarily represent those forms which would be produced as a result of an accidental release from a nuclear power plant or as a result of controlled release from nuclear fuel reprocessing facilities such as those which occur at Windscale in England. 

Amme, M. 2002. Contrary effects of the water radiolysis product H2O2 upon the dissolution of nuclear fuel in natural ground water and deionized water. Radiochimica Acta, 90, 399-406. 

Oversby, V. M. 1999. Uranium Dioxide, SIMFUEL, and Spent Fuel Dissolution Rates - A Review of Published Data. Swedish Nuclear Fuel and Waste Management Co., Stockholm, Sweden, TR-99-22. 

Sunder, S., Shoesmith, D. W. Miller, N. H. 1997. Oxidation and dissolution of nuclear fuel (UO2) by the products of the alpha radiolysis of water. Journal of Nuclear Materials, 244, 66-74. 

Reprocessing is based on liquid-liquid extraction for the recovery of uranium and plutonium from used nuclear fuel (PUREX process). The spent fuel is first dissolved in nitric acid. After the dissolution step and the removal of fine insoluble solids, an organic solvent composed of 30% TriButyl Phosphate (TBP) in TetraPropylene Hydrogenated (TPH) or Isopar L is used to recover both uranium and plutonium the great majority of fission products remain in the aqueous nitric acid phase. Once separated from the fission products, back-extraction combined with a reduction of Pu(I V) to Pu(III) allows plutonium to be separated from uranium these two compounds can be recycled.2... 

Since publication of this work, Japanese researchers have undertaken an effort to demonstrate the feasibility of direct dissolution of U02 from spent nuclear fuels by the TBP-HN03 complex in SC-C02.49 Ultimately, the project is directed at the extraction of both uranium and plutonium from mixed oxide fuels and from irradiated nuclear fuel. Ideally, soluble uranyl and plutonium nitrate complexes will form and dissolve in the C02 phase, leaving the FPs as unwanted solids. As in the conventional... 

Figure 7 Electrochemical photothermal deflection spectroscopy experiment (0.5 mol dm-3 Na2S04 pH = 10.5, 20 mV s 1), illustrating the detection of the onset of dissolution of nuclear fuel (U02) (A) voltammetric response for scans to various anodic potential limits (B) and (C) probe beam deflection for each scan. The deflection of the probe beam is proportional to the dissolved uranium concentration, and deflection of the probe beam towards the electrode surface is an indication that dissolution is occurring (Reprinted from Ref. 2 with permission from Elsevier Science S.A.)...

Figure 13 Electrochemically determined anodic dissolution currents recorded on a rotating nuclear fuel (U02) disk (co = 16.7 Hz) in 0.1 mol dm-3 NaC104 (pH = 9.5) containing various amounts of carbonate ( ) 0.005 mol dm-3 (A) 0.01 (X) 0.05 (O) 0.1. Line 1 is the line that would fit the dissolution currents recorded with no carbonate present. Line 2 is a line of the same slope as line 1 shifted up two orders of magnitude in current.

Figure 15 Procedure used to obtain a database of nuclear fuel (U02) corrosion rates (currents) (B) from a Tafel relationship for the anodic dissolution currents for U02 and a series of EC0Rr values measured in radiolytically decomposed solutions (A).

One of the key processes here is the dissolution of the spent nuclear fuel matrix in groundwater liberating radioactive fission products and actinides. Without this process no radioactivity will be released to the biosphere. 

One of the most extensively studied systems, due to its high importance, is dissolution of spent nuclear fuel in aqueous solution. For this reason, many of the examples used in this chapter originate from this field of studies. 

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