PNNL

Abstract

For an efficient nuclear waste vitrification process at the Waste Treatment and Immobilization Plant (WTP) on the Hanford Site, proper selection and consistent supply of glass-forming chemicals (GFCs) are crucial. Thorough characterization of the GFCs is required to reduce risks in operation of the vitrification facility. Low-activity waste (LAW) will be blended with GFCs to form slurry feeds and then fed to melters and vitrified. To enhance properties of waste glasses, new chemicals are being introduced to the current GFC mixture. , , In this study, three new GFCs were evaluated for enhanced LAW glass formulations: chromium oxide (Cr2O3), vanadium oxide (V2O5), and stannic oxide (SnO2). These three oxide components are included in enhanced waste glass formulations, and GFCs with the appropriate physical and flow properties are needed. As a starting point, single metal oxide GFCs, Cr2O3, V2O5, and SnO2, were sourced and tested. Then, alternative sources of Sn and Cr (SnO and FeCr2O4) were tested along with an alternative zircon source (ZrSiO4). This report documents the work performed to collect physical and flow property data on these new GFCs and melter feed slurries generated using these GFCs and simulated low-activity wastes. To characterize these new individual GFCs and mixtures of the GFCs, an industrial bulk characterization consultant, Jenike and Johanson, was employed to measure physical and flow properties of individual GFCs and their mixtures. Pacific Northwest National Laboratory (PNNL) also measured several selected physical properties including data evaluation as a quality assurance step. In addition, PNNL measured physical and rheological properties of melter feeds containing these GFCs. All new individual GFCs, except for ZrSiO4, used for this study were not considered as the original baseline 13 GFCs currently planned or used at the WTP. Therefore, these new GFCs may need to replace other existing GFCs or require new silos. Based on the measured property data and fundamental information of storage design, Cr2O3, SnO2, and FeCr2O4 are not suggested to be used because of issues with ratholing, bridging, and caking. V2O5 and SnO might be acceptable to be used but can also raise concerns for stagnant materials in the silo with insufficient wall angle. Bead-type ZrSiO4 does not raise any concerns for use in current silos and hoppers. GFC mixtures and melter feeds tested in this study did not raise any issues for use at the WTP.