Large scale leach testing of DWPF canister sections

A Large-Scale Leach Test Facility (LSLTF) has been constructed at the US Department of Energy's Savannah River Laboratory (SRL) to perform static leach tests on 24-inch (610 mm)-diameter canister sections cut from simulated (nonradioactive) waste forms cast under reference conditions. The equipment and test procedures are designed to closely correspond to MCC-1 leach test criteria. Less than a factor of 3 increase in leachability results from combined scale-up, glass-cracking, leached surface area estimation, and surface roughness effects. This factor is dominated by surface roughness of saw cut surfaces. The factor is negligible when compared to the 200,000/l ratio of glass sample masses. The MCC-1, and other small-scale leach tests have been valuable in determining the relative merits of alternative waste form compositions. However, the actual waste glass to be stored in repositories is subject to fracture, devitrification, and container/glass interactions, which are difficult to simulate on a laboratory scale. Large-scale leach tests integrate these and other possible waste form characteristics that are not represented in typical small samples. The facility, equipment, test method and results of one year leach testing are discussed. These results substantiate the applicability of small scale test data which precede this work, and the use of small scale tests to simulate leaching of the Defense Waste Processing Facility's borosilicate glass product. Exceptionally good sampling statistics make the large scale data particularly well suited for verification of models of leachability rates. 2 references, 6 figures, 2 tables