The Formation of Pu(IV)-Colloid by the Alpha-reduction of Pu(V) or Pu(VI) in Aqueous Solutions

The effects of alpha-particle self-irradiation have been investigated in solutions of {sup 239}Pu in the pH range from 1.3 to > 2.2. The initial solutions contained Pu(VI), Pu(V), colloidal Pu(IV) or various mixtures of these. Composition versus time was determined for periods up to 618 days. Colloidal Pu(IV) formed slowly in mixtures with initial average oxidation states greater than about 4.5. Colloidal Pu(IV) reacts slowly to give mixtures of Pu(V) and Pu(VI). The two most important reactions in the system appear to be: the disproportionation of Pu(V) to give Pu(VI) and colloidal Pu(IV), and the alpha-particle induced reduction of Pu(VI) to give Pu(V). Steady-states were reached very slowly and required at least 400 days for most of the mixtures. No evidence was found for equilibrium in the disproportionation reaction. 20 refs., 4 figs., 3 tabs.