Liquidus Temperature Studies In Support Of The Incorporation Of Small Column Ion Exchange Streams In Defense Waste Processing Facility High Level Waste Glass

This report documents the last of a series of studies on the potential impacts of Small Column Ion Exchange (SCIX) on Defense Waste Processing Facility (DWPF) glass. It was previously recommended that full liquidus temperature (TL) measurements be completed for those glasses where a TL range had only been estimated. These data would then be available to support refitting of the TL model to allow for the application of the model to glasses with higher TiO2 concentrations. It was also recommended that all further TL experiments utilize glass compositions that include noble metals, since the noble metals can act as nucleation sites and lead to enhanced crystallization. The KT07- and KT10-series glasses were recommended for further TL measurements since these glasses included noble metals. The KT06-series glasses were also recommended for further TL measurements since they targeted a broad range of compositions for potential DWPF operation. However, since these glasses did not contain noble metals, it was necessary to fabricate additional glasses with noble metals added, designated as the KT06NMseries. Chemical composition measurements showed that there were only minor difficulties in meeting the targeted concentrations for the KT06NM glasses. Some deviations from the targeted composition were seen for composition KT06NM-04, although the deviations did not impact the outcome of the study since the measured composition for this glass will be used in future evaluations of TL. The measured TL for the KT07- and KT10-series glasses were all higher than the upper bounds of the 95% confidence intervals of the model predicted values. The model under predicted the TL for all of these glasses that had elevated TiO2 concentrations (approximately 4 to 7 wt %). One must keep in mind that the TiO2 concentrations of these glasses are well above the region of applicability defined for the current TL model of 0-1.85 wt % TiO2; therefore, this prediction bias is not necessarily unexpected. These data should be useful in refitting the model to allow for applicability to higher concentrations of TiO2 in DWPF glasses. The TL measurements for the KT06NM-series glasses were not completed due to the limited time available for the study (the SCIX program will be suspended effective October 2011). The data collected to date, as well as all of the glass samples, will be archived at the Savannah River National Laboratory (SRNL) for future use. The TL measurements for the KT06NM-series glasses should be completed to allow for the updating of the TL model for high TiO2 concentration glasses. This data set of high TiO2 concentration glasses and measured TL values can be combined with the glass compositions and properties previously used in developing the DWPF TL model so that the model can be extended to higher concentrations of TiO2 in glass. Should SCIX be displaced by another salt processing technology at the Savannah River Site (SRS), these data will remain valuable since it will likely be necessary to incorporate higher concentrations of Monosodium Titanate (MST) from the Salt Waste Processing Facility (SWPF) into DWPF glass. These data will also be useful in modifying the DWPF Product Composition Control System (PCCS) models to allow for the incorporation of higher waste loadings in future sludge batches.