Extraction and separation of Se, Zr, Pd, and Cs including long-lived radionuclides

Abstract

The solvent extraction of Se(IV), Zr(IV), Pd(II), and Cs(I) from nitric acid into 1-octanol (OC), or 1-octanol and n-dodecane has been performed. These elements include long-lived radionuclides in spent nuclear fuels, so a simple separation method is indispensable for the development of the treatment of high-level liquid radioactive waste. It was found that Se can be extracted using phenylenediamine, Zr(IV) can be extracted using tetraoctyl diglycolamide and di-2-ethylhexyl phosphoric acid, and Pd can be extracted using (methylimino)bis(N,N-dioctylacetamide) and N,N,N',N',N",N"-hexaoctylnitrilotriacetamide. These elements can be recovered in over 90% yield by these extractants from nitric acid into OC. A distribution ratio of Cs(I) of greater than 1 can be obtained using di-t-butyldibenzo-18-crown-6. It is clear that 90% recovery of Cs(I) can be achieved using an extraction solvent with ten times the volume of the aqueous phase.