Fission products, extraction

Fission Product Extraction. Tables IV and V list the distribution ratios for most of the fission products produced in spent fuel. Also included are corrosion products Cr, Fe, and Ni. Extractant concentrations for DHDECMP, HHDECMP, and 0c >D[IB]CMP0 were selected on the basis of data in Figure 2. The aqueous acidity... 

Riddle, C.L., Baker, J.D., Law, J.D. et al. 2005. Fission product extraction (FPEX) Development of a novel solvent for the simultaneous separation of strontium and cesium from acidic solutions. Solvent Extr. Ion Exch. 23 (3) 449 -61. 

Yamaura, M. Matsuda, H.T. Actinides and fission products extraction behavior in TBP/ XAD7 chromatographic column, J. Radioanal Nucl. Chem. 224 (1997) 83-87. 

This process, allowing coextraction of strontium and cesium, has been named the Fission Product Extraction process (FPEX). 

Derivation A fission product extracted from irradiated nuclear fuel. 

Fission product recovery may alleviate some waste storage problems but will not nullify the need for low-level waste processing. Indeed, any fission product extraction process will, by its inevitable inefficiency, generate low-level wastes. Thus, continued research and development in the field of low-cost waste processing techniques, is probably justifiable. 

In this acidity range, fission product extraction was found to be maximum In the 0-lM nitric acid region. The partition coefficient, d p. In this region was greatest with methyl-propyl ketone (22 x 10 at O.6IH) and least with metdiyl-hexyl ketone (2.4 x 10 at O.03M). In the acid-deficient region, Upp Increased as the acld-deflclency was decreased (the solution was made more acidic). After the maximum otpp was reached In the 0-lM acid region, the partition coefficient was decreased and then Increased as the aqueous solution was made more acidic up to 3-4M. The partition... 

Uranium Purification. Subsequent uranium cycles provide additional separation from residual plutonium and fission products, particularly zirconium— niobium and mthenium (30). This is accompHshed by repeating the extraction/stripping cycle. Decontamination factors greater than 10 at losses of less than 0.1 wt % are routinely attainable. However, mthenium can exist in several valence states simultaneously and can form several nitrosyl—nitrate complexes, some for which are extracted readily by TBP. Under certain conditions, the nitrates of zirconium and niobium form soluble compounds or hydrous coUoids that compHcate the Hquid—Hquid extraction. SiUca-gel adsorption or one of the similar Hquid—soHd techniques may also be used to further purify the product streams. 

The first successflil production method for the separation of Pu from U and its fission products was the bismuth phosphate process, based on the carrying of Pu by a precipitate of BiPO (126). That process has been superseded by Hquid-Hquid extraction (qv) and ion exchange (qv). In the Hquid-Hquid... 

Cesium isotopes can be recovered from fission products by digestion in nitric acid, and after filtration of waste the radioactive cesium phosphotungstate is precipitated using phosphotungstic acid. This technique can be used to prepare radioactive cesium metal or compounds. Various processes for removal of Cs isotopes from radioactive waste have been developed including solvent extraction using macrocycHc polyethers (62) or crown ethers (63) and coprecipitation with sodium tetraphenylboron (64). 

Then the fuel elements are dissolved in 7m HNO3 to give a solution containing U and Pu which, in the widely used plutonium-uranium-reduction, or Purex process, are extracted into 20% tributyl phosphate (TBP) in kerosene leaving most of the fission products... 

Three classes of carbamoylmethylphosphoryl extractants were studied for their ability to extract selected tri-, tetra-, and hexavalent actinides from nitric acid. The three extractants are dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP), hexyl hexyl-N,N-diethylcarbamoylmethylphosphinate (HHDECMP), and octyl(phenyl)-N,N-diisobutylcarbamoylmethylphos-phine oxide 0< >D[IB]CMP0. The above three extrac-trants were compared on the basis of nitric acid and extractant dependencies for Am(III), solubility of complexes on loading with Nd(III) and U(VI), and selectivity of actinide(III) over fission products. 

We have studied the extractant behavior of a series of compounds containing the carbamoylmethylphosphoryl (CMP) moiety in which the basicity of the phosphoryl group and the steric bulk of the substituent group are varied (10,LL). These studies have led to the development of extractants which have combinations of substituent groups that impart to the resultant molecule improved ability to extract Am(III) from nitric acid and to withstand hydrolytic degradation. At the same time good selectivity of actinides over most fission products and favorable solubility properties on actinide loading are maintained (11). 

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