RADIATION-CHEMICAL BEHAVIOR OF ACTINIDES IN EXTRACTION SYSTEMS .7. OXIDATION OF U(IV) IN SOLUTIONS OF TBP IN NORMAL-DODECANE

The radiation-chemical behavior and chemical oxidation of U(IV) in 30% TBP-n-dodecane is studied by spectrophotometry. The solution is deaerated with Ar in the presence (0.01 M) and absence of diphenylamine (DPA) for 1.7.10(-2) M metal in the gamma-radiation absorbed dose range from 3.6.10(2) to 5.8.10(4) Gy. The stability of U(IV) in the deaerated 30% TBP-n-dodecane increases in the presence of DPA. The gamma-radiation absorbed dose at which U(IV) is practically completely oxidized to U(VI) in systems with and without DPA are 5.4.10(4) and 7.5.10(3) Gy, respectively. The quantity E at which U(IV) is completely oxidized in the system with DPA without deaeration is 1.6.10(4) Gy. Mechanisms of chemical (nonradiational) and radiation-chemical oxidation of U(IV) in aerated and deaerated solutions in the presence of the acceptor HNO2 (DPA) and in deaerated solutions without DPA are proposed. The rate constants and radiation-chemical yield so U(IV) are calculated.