Plutonium Solubility in Simulated Savannah River Site Waste Solutions

To address the accelerated disposition of the supernate and salt portions of Savannah River Site (SRS) high level waste (HLW), solubility experiments were performed to develop a predictive capability for plutonium (Pu) solubility. A statistically designed experiment was used to measure the solubility of Pu in simulated solutions with salt concentrations and temperatures which bounded those observed in SRS HLW solutions. Constituents of the simulated waste solutions included: hydroxide (OH−), aluminate , sulfate , carbonate , nitrate , and nitrite anions. Each anion was added to the waste solution in the sodium form. The solubilities were measured at 25 and 80°C. Five sets of samples were analyzed over a six month period and a partial sample set was analyzed after nominally fifteen months of equilibration. No discernable time dependence of the measured Pu concentrations was observed except for two salt solutions equilibrated at 80°C which contained OH− concentrations >5 mol/L. In these solutions, the Pu so...