Infrared Imaging for the Control and Optimization of Waste Treatment by Vitrification

The U.S. Department of Energy (DOE) Office of River Protection (ORP) contracted with AMEC, GeoMelt Division (GeoMelt), to develop and demonstrate its Bulk Vitrification (Bulk Vit) technology using the In-Container VitrificationTM, a.k.a. ICVTM, (ICV) process. This process is being evaluated as a potential supplemental treatment process for a large fraction of the DOE Hanford Site low-activity waste (LAW). The ICV process is a batch or hybrid batch-feed thermal waste treatment process that is performed in a refractory-lined steel container. Waste and glass-formers (if needed) are placed into the ICV container and are melted using Joule (resistive) heating. Most waste constituents are either destroyed or decomposed during treatment and any remaining hazardous constituents, such as radionuclides, are encapsulated in the highly durable glass product. GeoMelt recently demonstrated Bulk Vit to the DOE at full-scale using a 24-ft x 8-ft x 8-ft ICV melter, processing 56 metric tons (MT) of liquid Hanford LAW waste simulant and glass formers in a single contained melt. This test, the most recent of five full-scale tests for the project, called Test FS-38D, also incorporated a full-scale liquid waste drying system, which dried and mixed the liquid LAW simulant with glass forming minerals prior to vitrification. After drying and mixing, the waste simulant was then periodically fed to the ICV melter, where it was vitrified into a borosilicate glass block weighing 44 MT. Accurately monitoring and controlling the amount of waste material added to the ICV is an essential and sometimes challenging task. It was determined during early project testing that direct visual observation of conditions within the melt container was needed to ensure that feed was being properly supplied and optimally distributed and incorporated across the melt surface. Standard video systems have historically been used for GeoMelt operations, but only with marginal results. Little or no lighting, high particulate concentration, and high concentration of condensing gasses such as NOx inside the container plenum are demanding conditions for a video system. Efforts were undertaken prior to Test FS-38D to identify and demonstrate an improved monitoring system for future Bulk Vit operations. Infrared imaging was investigated with the expectation that the challenging environmental conditions could be overcome. IR systems are able to operate with no supplemental lighting and some have the unique ability to resolve and image in dusty or opaque gas environments. In addition, these IR systems can provide both qualitative and quantitative measurements of waste and molten glass temperatures during waste processing. A Mikron Infrared Inc. imaging system was selected as the best candidate for the Bulk Vitrification system, and was demonstrated during engineering-scale testing. The system was then implemented during full-scale Test 38D, and met or exceeded all test objectives. The system was able to provide excellent imagery throughout the test period, and it enabled operations personnel to precisely control the feed addition to the ICV container. The primary test objectives for FS-38D were met in large part due to this newly implemented monitoring system, and the equipment has been included in the Hanford Demonstration Bulk Vitrification System (DBVS) final design package. (authors)