THE PHOTOCHEMICAL BEHAVIOUR OF Pu(IV)

The effects of concentration of H+ and NO3- on the photochemical behaviour of Pu(Ⅳ) in perchloric acid solution (ionic strength = 3) have been investigated. The results show that the photochemical oxidation of Pu(Ⅳ) to Pu(Ⅵ)is obviously promoted by nitrate ion.Results of the study of thermo-disproportionation of Pu(Ⅳ) in perchloric acid solution (ionic strength = 3)at 63℃ and irradiation of ultraviolet beam at the same experimental condition show that the light irradiation with ultraviolet beam promotes the disproportionation of Pu (Ⅳ) , and ratios of reaction concentration quotient [Pu(Ⅲ)]2-[Pu(Ⅵ)]/[Pu(Ⅳ)]3 arc determined as 2.2×103, 4.15×102, 1.98×102 and 3.16×102 at H+ equal to 1.0, 1.5, 2.0 and 3.0 mol/1.The effects of CH3OH, C2H5OH, UO22+ and Fe3+ on the photochemical behaviour of Pu(Ⅳ) in nitrate solution are also studied. The results show that the Pu(Ⅳ) oxidation to Pu(Ⅵ) is inhibited by ferric ion, the quantity of Pu(Ⅵ) can be decreased from 80% to 10% if the concentration of ferric ion is 0.038 mol/1. The probable reason of inhibition of Pu(Ⅳ) oxidation to Pu(Ⅵ) by ferric ion is discussed.