Studies on hydrolysis and radiolysis of N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide

Summary

Hydrolytic and radiolytic stabilities of a promising extractant, N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA), for actinides in high-level radioactive liquid waste from nuclear fuel reprocessing were investigated in air at room temperature. Hydrolysis by nitric acid was not observed, whereas radiolysis by gamma irradiation was notably observed. The radiolysis study showed that an amide-bond, an ether-bond, and a bond adjacent to the ether-bond tended to be broken by gamma irradiation, and dioctylamine and various N,N-dioctylmonoamides were identified as the main degradation products by GC/MS and NMR analyses. The G-value for degradation of neat TODGA was 8.5 ± 0.9, which value was higher than those for N,N′-dioctyl-N,N′-dimethyl-2-(3′-oxapentadecyl)-propane-1,3-diamide and N,N-dioctylhexanamide. It was obvious that n-dodecane, which was used for a diluent, had a sensitization effect on the radiolysis of these amidic extractants. In a TODGA–n-dodecane–HNO₃ system, the coexisting nitric acid showed an insignificant effect on the radiolysis of TODGA.