Dissolution of plutonium oxide in nitric acid at high hydrofluoric acid concentrations

The dissolution of plutonium dioxide in nitirc acid (HNO3) at high hydrofluoric acid (HF) concentrations has been investigated. Dissolution rate curves were obtained using 12M HNO3 and HF at concentrations varying from 0.05 to 1.0 molar. The dissolution rate increased with HF concentration up to 0.2M and then decreased at higher concentrations. There was very little plutonium dissolved at 0.7 and 1.0M HF because of the formation of insoluble PuF4. Various oxidizing agents were added to 12M HNO3-1M HF dissolvent to oxidize Pu(IV) to Pu(VI) and prevent the formation of PuF4. Ceric [Ce(IV)] and silver [Ag(II)] ions were the most effective in dissolving PuO2. Although these two oxidants greatly increased the dissolution rate, the rates were not as rapid as those obtained with 12M HNO3-0.2M HF