Characterization and leaching behavior of plutonium-bearing Synroc-C

Synroc-C containing 10 wt% simulated PW-4b-D HLW including 0.62 wt% {sup 239}Pu was subjected to MCC-1 type leach tests at 70 C in deionized water, silicate and carbonate leachates for 53 d and deionized water for 2,472 d. The normalized total (i.e., unfiltered leachate + vessel wall) Pu leach rates in deionized water, silicate and carbonate leachates for periods up to 53 d were found to be of the order of 10{sup {minus}5}, 10{sup {minus}4} and 10{sup {minus}4} g/m{sup 2} d respectively. After 2,472 d, the differential, normalized, Pu leach rate in deionized water dropped to {approximately}5 {times} 10{sup {minus}6} (total) and {approximately}5 {times} 10{sup {minus}8} (solution--after filtration through a 1,000 NMW filter) g/m{sup 2}d. SEM and AEM were used to characterize the starting material and investigate the secondary phases on the surfaces of leached Synroc-C discs. Calculated and measured normalized Pu leach rates are compared and the partitioning of Pu between zirconolite and perovskite is discussed.