Application of the Evacuated Canister System for Removing Residual Molten GlassFrom the West Valley Demonstration Project High-Level Waste Melter

摘要

The principal mission of the West Valley Demonstration Project (WVDP) is to meet a series of objectivesdefined in the West Valley Demonstration Project Act (Public Law 96-368). Chief among these is theobjective to solidify liquid high-level waste (HLW) at the WVDP site into a form suitable for disposal in afederal geologic repository. In 1982, the Secretary of Energy formally selected vitrification as thetechnology to be used to solidify HLW at the WVDP.One of the first steps in meeting the HLW solidification objective involved designing, constructing andoperating the Vitrification (Vit) Facility, the WVDP facility that houses the systems and subsystems usedto process HLW into stainless steel canisters of borosilicate waste-glass that satisfy waste acceptancecriteria (WAC) for disposal in a federal geologic repository. HLW processing and canister productionbegan in 1996. The final step in meeting the HLW solidification objective involved ending Vit systemoperations and shutting down the Vit Facility. This was accomplished by conducting a discrete series ofactivities to remove as much residual material as practical from the primary process vessels, components,and associated piping used in HLW canister production before declaring a formal end to Vit systemoperations.Flushing was the primary method used to remove residual radioactive material from the vitrificationsystem. The inventory of radioactivity contained within the entire primary processing system diminished byconducting the flushing activities. At the completion of flushing activities, the composition of residualmolten material remaining in the melter (the primary system component used in glass production) consistedof a small quantity of radioactive material and large quantities of glass former materials needed to produceborosilicate waste-glass.A special system developed during the pre-operational and testing phase of Vit Facility operation, theEvacuated Canister System (ECS), was deployed at the West Valley Demonstration Project to remove thisradioactively dilute, residual molten material from the melter before Vit system operations were brought toa formal end.The ECS consists of a stainless steel canister of the same size and dimensions as a standard HLW canisterthat is equipped with a special L-shaped snorkel assembly made of 304L stainless steel. Both the canisterand snorkel assembly fit into a stainless steel cage that allows the entire canister assembly to be positionedover the melter as molten glass is drawn out by a vacuum applied to the canister. This paper describes theprocess used to prepare and apply the ECS to complete molten glass removal before declaring a formal endto Vit system operations and placing the Vit Facility into a safe standby mode awaiting potentialdeactivation.