AN EXPERIMENTAL ASSESSMENT OF THE IMPACT OF SLUDGE VARIATION ON THE FRIT 202-A11 - SB3 GLASS SYSTEM

Twenty-seven glasses were designed to assess the impacts of both sludge variation ({+-}5 or {+-}10% for the major sludge components) and waste loading (WL) (50 or 52%) on the Product Consistency Test (PCT) response after two thermal histories (quenching and a modified ccc schedule) within the Frit 202-A11-Sludge Batch 3 (SB3) system. The PCT results of the quenched glasses (regardless of compositional view) indicate that all Frit 202-A11-Sludge SB3 (referred to as HTLG) variability study glasses are very acceptable relative to the Environmental Assessment (EA) glass benchmark. More specifically, the normalized boron releases (NL [B] in g/L) range from 0.8 g/L (for HTLG-60VS based on the measured composition) to 1.384 g/L (HTLG-79VS based on the measured bias-corrected (bc) composition). These results can be compared to the NL [B] for the EA benchmark of 16.695 g/L. The PCT results of the quenched glasses are consistent with previous data in the Frit 202-A11-SB3 system. The PCT results for the ccc glasses are not as straight forward. The NL [B]s for the slow cooled glasses range from 0.607 g/L (for HTLG-57ccc based on the measured composition) to 9.42 g/L (for HTLG-67ccc based on the measured bc compositional view). Although these glasses would be classified as acceptable relative to the EA glass benchmark, the relatively high release of the slow cooled glasses would be of concern if this system were to be implemented into the Defense Waste Processing Facility (DWPF). The PCT responses for those glasses in which either nepheline or both nepheline and aegirine formed upon slow cooling lead to a significant reduction in PCT response. Although the formation of aegirine has (in general) a slightly negative impact on the PCT response, the formation of nepheline and aegirine is a combination that has a high probability of leading to a significant reduction in durability upon slow cooling. With respect to the Cold Crucible Induction Melter (CCIM) demonstration, a clear cut delineation of sludge compositions and/or targeted WLs is desirable to avoid the formation of either of these phases. However, based on a statistical assessment of the PCT and X-ray diffraction (XRD) data, this direct relationship does not appear to exist for this sludge/frit system and identifying the nepheline and/or aegirine primary phase field is not readily apparent based on the limited data. In addition, the possibility to target higher WLs (> 50%) to avoid any negative impacts on durability as a result of crystallization, as previously done with the nominal SB3 composition, was dependent upon the sludge component combinations. Moreover, when composition variation is applied to the sludge, multiple sludge and frit combinations fall within the nepheline and/or aegirine phase fields even at 52% WL, which ultimately lead to a negative impact on durability. Nonetheless, the PCT results do suggest that the probability of observing the negative impact is lower at the higher WLs. Only 2 of the inner layer, 52% WL based glasses have NL [B] > 2 g/L after slow cooling as compared to 4 of the 9 inner layer EVs targeted 50% WL