Plutonium and Americium Alpha Radiolysis of Nitric Acid Solutions

The yield of HNO2, as a function of absorbed dose and HNO3 concentration, from the alpha-radiolysis of aerated HNO3 solutions containing plutonium or americium has been investigated. There are significant differences in the yields measured from solutions of the two different radionuclides. For 0.1 mol dm(-3) HNO3 solutions, the radiolytic yield of HNO2 produced by americium alpha-decay is below the detection limit, whereas for plutonium alpha-decay the yield is considerably greater than that found previously for gamma-radiolysis. The differences between the solutions of the two radionuclides are a consequence of redox reactions involving plutonium and the products of aqueous HNO3 radiolysis, in particular H2O2 and HNO2 and its precursors. This radiation chemical behavior is HNO3 concentration dependent with the differences between plutonium and americium alpha-radiolysis decreasing with increasing HNO3 concentration. This change may be interpreted as a combination of alpha-radiolysis direct effects and acidity influencing the plutonium oxidation state distribution, which in turn affects the radiation chemistry of the system.