KINETIC AND SOLVENT-EXTRACTION STUDIES OF THE SELECTIVE REDUCTION OF NP(VI) BY NEW SALT-FREE REDUCING AGENTS

A variety of salt free organic reducing agents (carboxylic acids, alde hydes, ketones, guanidines and substituted hydrazines) have been scree ned for their reactivity with Np(VI) and Pu(IV) ions. The objective wa s to find reductants that have fast kinetics for Np(VI) reduction but which also showed a high selectivity for Np(VI) reduction over Pu(IV). Substituted hydrazines, particularly 1,1-dimethyl hydrazine and tert- butyl hydrazine, were shown to be the most promising of the screened r eductants. The kinetics of Np(VI) and Pu(TV) reduction reactions with 1,1-dimethyl hydrazine and tert-butyl hydrazine were studied in greate r detail and demonstration solvent extraction experiments were perform ed. The reduction of Pu(TV) was shown to be enhanced in the presence o f U(VI) and this made 1,1-dimethyl hydrazine unsuitable as a selective reductant. Tert-butyl hydrazine may however show some promise as a se lective reductant for Np(VI) under carefully controlled conditions.