Enhancement of Glass Production Rate in Joule Heated Ceramic Melter

In this research work, experimental studies and numerical simulation of Joule Heated Ceramic Melter (JHCM) used for vitrification of radioactive liquid waste (RLW) were carried out. The isolation of the long-lived radioactive isotopes by fixing them in suitable host matrix is the only practical approach adopted for conditioning of highly radioactive waste generated from the nuclear fuel cycle. RLW and preformed glass beads are added simultaneously on a molten glass pool maintained at 1000 °C in JHCM to form a product that is qualified for long term storage. The sequence and kinetics of different reactions taking place in JHCM were identified and calculated by carrying out Thermogravimetric Analysis of the radioactive species present in RLW at different heating rates. The effects of these constituents on the melter throughput and quality of the Vitrified Waste Product (VWP) produced were assessed. The foam generated during vitrification process has a major influence on the design of melters. The amount of foam generated was quantified and its influence on glass production rate was analyzed. Melt rate limitations were determined for JHCM based on the measured thermo-physical properties. Minimum residence time required for producing product of the desired specification is determined. A model is developed for determining the glass melting rates. Experiments were carried out for generating data required for validation of the model. The model predictions are compared with experimental results. The factors affecting the product throughput and quality are identified with an objective of reducing the residence time of the product thereby increasing the throughput. The effect of agitation on the rate of melting of glass was determined.

Lessons Learned Siting and Successfully Processing U.S. DOE Radioactive Wastes Using a High Throughput Vitrification Process

This paper describes actual experience applying a technology to achieve volume reduction while producing a stable waste form for low and intermediate level liquid (L/ILW) wastes, and the L/ILW fraction produced from pre-processing of high level wastes. The chief process addressed will be vitrification. The joule-heated ceramic melter vitrification process has been used successfully on a number of waste streams produced by the U.S. Department of Energy (DOE). This paper will address lessons learned in achieving dramatic improvements in process throughput, based on actual pilot and full-scale waste processing experience. Since 1991, Duratek, Inc., and its long-term research partner, the Vitreous State Laboratory of The Catholic University of America, have worked to continuously improve joule heated ceramic melter vitrification technology in support of waste stabilization and disposition in the United States. From 1993 to 1998, under contact to the DOE, the team designed, built, and operated a joule-heated melter (the DuraMelterTM) to process liquid mixed (hazardous/low activity) waste material at the Savannah River Site (SRS) in South Carolina. This melter produced 1,000,000 kilograms of vitrified waste, achieving a volume reduction of approximately 70 percent and ultimately producing a waste form that the U.S. Environmental Protection Agency (EPA) delisted for its hazardous classification. The team built upon its SRS M Area experience to produce state-of-the-art melter technology that will be used at the DOE’s Hanford site in Richland, Washington. Since 1998, the DuraMelterTM has been the reference vitrification technology for processing both the high level waste (HLW) and low activity waste (LAW) fractions of liquid HLW waste from the U.S. DOE’s Hanford site. Process innovations have doubled the throughput and enhanced the ability to handle problem constituents in LAW. This paper provides lessons learned from the operation and testing of two facilities that provide the technology for a vitrification system that will be used in the stabilization of the low level fraction of Hanford’s high level tank wastes.

High Level Liquid Waste Solidification Using a “Cold” Crucible Induction Melter

ABSTRACTAt the present time the primary problem in a closed nuclear fuel cycle is the management of high level liquid waste (HLLW) generated by the recovery of uranium and plutonium from spent nuclear fuel. Long-term storage of the HLLW, even in special storage facilities, poses a real threat of ecological accidents. This problem can be solved by incorporating the radioactive waste into solid fixed forms that minimize the potential for biosphere pollution by long-lived radionuclides and ensure ecologically acceptable safe storage, transportation, and disposal. In the present report, the advantages of a two-stage HLLW solidification process using a “cold” crucible induction melter (CCIM) are considered in comparison with a one-stage vitrification process in a ceramic melter.This paper describes the features of a process and equipment for a two-stage HLLW solidification technology using a “cold” crucible induction melter (CCIM) and identifies the advantages compared to a one-stage ceramic melter. A two-stage pilot facility and the technical characteristics of the equipment are described using a once-through evaporator and cold-crucible induction melter currently operational at the IA.Mayak. facility in Ozersk, Russia. The results of pilot-plant tests with simulated HLLW to produce a phosphate glass are described. Features of the new mineral-like waste form matrices synthesized by the CCIM method are also described. Subject to further development, the CCIM technology is planned to be used to solidify all accumulated HLLW at Mayak – first to produce borosilicate glass waste forms and then mineral-like waste forms.