PLUTONIUM(III) OXIDATION UNDER ALPHA-IRRADIATION IN NITRIC-ACID SOLUTIONS

Plutonium(III) oxidation under high energy alpha-irradiation in nitric acid solutions has been studied relative to concentrations of both nitric acid (0.12-2.9 mol/1) and plutonium (1.4-10 mmol/1) using spectrophotometric techniques. Curium-244 has been used as the basic alpha-irradiation source. It has been stated that in solutions with nitric acid concentrations lower than 0.5 mol/1 plutonium(III) does not oxidize completely. In the course of the process the formation of a plutonium(IV) peroxide complex is observed. Increase in the nitric acid concentration results in that in both the rate and degree of plutonium(III) oxidation. When (c)HNO3 is higher than 0.5 mol/1 the peroxide complex does not form and the process assumes an autocatalytic character. It has also been shown that plutonium(III) oxidation kinetics is significantly affected by nitrous acid, one of the nitrate ion radiolysis products. To describe plutonium chemical transformations under irradiation in nitric acid solutions, a kinetic scheme is proposed. The calculations have been carried out on a BESM-6 computer; a satisfactory agreement between the calculated and experimental data has been obtained.