Glass Formulations for Immobilizing Hanford Low-Activity Wastes

Researchers at Pacific Northwest National Laboratory (PNNL) are developing and testing glasses for immobilizing low-activity wastes (LAW) for the full Hanford mission. PNNL is performing testing for low-activity waste glasses for both the Hanford Waste Treatment Plant (WTP) and the Bulk Vitrification Plant. The objective of this work is to increase the waste content of the glasses and ultimately increase the waste throughput of the LAW vitrification plants. This paper focuses on PNNL's development and testing of glasses for the Bulk Vitrification process. Collaborative studies are also being conducted with the Khlopin Radium Institute in St. Petersburg, Russia, to increase the solubility of sulfur in WTP glasses through the addition of trace chemicals to alter the glass chemistry. That research will be presented in a separate paper at this conference. Bulk Vitrification was selected as a potential supplemental treatment to accelerate the cleanup of LAW at Hanford. Also known as In-Container Vitrification{sup TM} (ICV{sup TM}), the Bulk Vitrification process combines soil, LAW, and chemical amendments; dries the mixture; and then vitrifies the material in a batch process in a refractory lined box. The process was developed by AMEC Earth and Environmental, Inc. (AMEC). Working with AMEC, PNNL developed a glassmore » formulation that could incorporate a broad range of Hanford LAW. The initial glass development involved a 'nominal' waste composition, and a baseline glass was formulated and tested at crucible, engineering, and full scales. The performance of the baseline glass was then verified using a battery of laboratory tests as well as engineering-scale and full-scale ICV{sup TM} tests. Continued testing has focused on developing an acceptable operating envelope for the baseline glass. The current glass constraints are: - 17 { =} 9.5 mass%; - 40 {<=} SiO{sub 2} {<=} 48.5 mass%. Multiple samples from engineering-scale and full-scale ICV{sup TM} tests performed with a baseline glass formulation developed from crucible tests were analyzed for chemical composition, Product Consistency Test, Vapor Hydration Test, and the Toxicity Characteristic Leaching Procedure. The results show good agreement between glasses prepared in a crucible in the laboratory and the glasses from the larger scale tests. The results also show that the glass in the ICV{sup TM} box is homogeneous. Future testing is planned for optimizing the glass waste loading and qualifying a broader range of waste streams for treatment in the Bulk Vitrification process. This paper reviews the glass development and qualification process completed to date. This includes several series of crucible studies as well as confirmation testing at engineering-scale and full-scale. This formulation paper complements information presented by AMEC in an ICV{sup TM} processing paper. (authors)« less