Crystallinity and solubility of Pu(IV) oxide and hydrous oxide in aged aqueous suspensions

The solubility and crystallinity of 238PuO2 (c, c=crystalline), 239PuO2 (c), and PuO2 x xH2O (a, a=amorphous) was monitored, over a period of 1300 days, to study the effect of aging these compounds in aqueous suspensions. 238PuO2 (c) was found to convert to a steady-state solid that had properties, including solubility, similar to that of Pu(IV) polymer. Both the 239PuO2 (c) and 239PuO2 x xH2O (a) converted to PuO2 (lc, lc=less crystalline) and hence had similar solubilities. The results indicated that regardless of whether one starts with PuO2 (c) or 239PuO2 x xH2O (a), the aging process, in which dehydration and crystallization is opposed by radiolytic effects, will convert these solids to a steady state material having properties between those of the true crystalline PuO2 and those of fresh hydrated oxide. (orig.)