PHOTOCHEMICAL OXIDATION OF NP(IV) AND PU(IV) IN CARBONATE SOLUTIONS SATURATED WITH N2O

Photooxidation of Np(IV) and Pu(IV) in carbonate and bicarbonate solut ions under UV irradiation of a mercury lamp was studied. In deaerated solutions Np(IV) is slowly oxidized to Np(VI), while Pu(IV) is stable. The rate of Np(IV) photooxidation sharply increases after saturation of solution with N2O, and complete conversion of Np(IV) (1 x 10(-4) M) into Np(VI) is reached within 2.5 h. The reaction is efficient at pH 8.4-12.0. Under irradiation of Pu(IV) solutions saturated with N2O, Pu (VI) is formed only at pH 11-12. Under these conditions, the complete oxidation of Pu(IV) to Pu(VI) is possible. The influence of other fact ors on Np(IV) and Pu(IV) photooxidation and mechanisms of reactions we re considered. The rate constants for Np(IV) reaction with CO3- radica ls were estimated.