Radiolysis and Hydrolysis of TRUEX-NPH solvent

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Abstract
The TRUEX solvent extraction process separates transuranic (TRU) elements from aqueous nitrate and chloride solutions. During contact with high-level wastes, which may be highly radioactive and highly acidic, the radiolysis and hydrolysis ofTRUEX-NPH solvent can affect the process not only by destroying the extractant CMPO in the solvent, but also by generating products of CMPO destruction, some of which are powerful extractants at low acidities and can prevent the stripping of Am and Pu from solvent that is to be recycled. To provide an experimental basis from which mathematical expressions of these effects could be derived, samples of solvent were degraded by radiolysis and hydrolysis while in contact with acidic aqueous solutions. Following this treatment, the distribution of americium between degraded solvent and aqueous HNO 3 was used as a measure of the extent of degradation. Mathematical expressions were derived to represent the distribution coefficient, D Am, as a function of hydrolysis time and/or radiation dose. Assumptions about the dependence of D Am on CMPO concentration were used to derive expressions for the hydrolysis rate for CMPO and also to calculate values of radiation chemical yield for CMPO radiolysis. Also experimentally investigated were changes in acidity of both the aqueousmore » and organic phases as functions of contact time, the effects of a carbonate wash in removing acidic degradation products that function as extractants at low acidities, and changes in compositions of some of the aqueous and organic phases during contact. « less

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