Session: 17-13-01: Plant Performance, Fluid Dynamics and Thermal Hydraulics in Energy and Power Applications

Paper Number: 164990

Heat Balance in the Wtp High Level Waste Melter 

Large-scale melters employ vitrification to convert legacy radioactive tank waste at the Hanford site into a stable glass waste form for long-term storage and disposal. Three-dimensional computational fluid dynamics (CFD) models of the High-Level Waste (HLW) Waste Treatment and Immobilization Plant (WTP) Joule-heated ceramic melters have been developed to understand the fluid dynamics and heat transfer within the melters during steady-state feed mode. The focus of this study is on the heat distribution in the melter system during normal operation between glass discharge periods. The overall melter heat balance considers three regions: the plenum, the cold cap, and the melt pool. The plenum is a voluminous gas-filled region comprised of air and reaction gases above the molten glass. The cold cap is formed by the addition of glass formers and waste feed added from the top of the melter that spreads across the surface of the melt pool. Heat is supplied to the melter via a pair of Inconel 690 side electrodes with a set point formulation in the model that maintains the melt pool at 1150 °C.  The glass is heated by electrical current passing through it due to its electrical resistivity. The enthalpy required to convert melter feed and glass formers to molten glass includes sensible heat, reaction heat, and water evaporation heat. Reaction heat, which is dependent on melter feed composition, is measured in the laboratory using thermal gravimetry–differential scanning calorimetry for various waste feed simulants. The cold cap acts as a heat sink due to the endothermic chemical reactions that convert the feed to glass. In the plenum region, heat is supplied by radiative heat transfer from areas of the molten glass surface not covered by the cold cap and by the hot conversion gases and bubbling air escaping from below the cold cap. Inleakage of ambient air through the melter lid ports, refractory brick, and penetrations helps cool the plenum gases. Gases escape through an outlet at the top of the melter and are funneled to the off-gas treatment, carrying away more sensible heat. Finally, heat losses through the melter walls occur due to radiation from the boundary surfaces, thermal radiation and convection in the plenum, and conduction from direct contact of the molten glass with the refractory-lined walls. Heat passes through the refractory brick and insulation layers to cooling panels, which keep the temperature of the stainless steel shell below structural limits. The use of detailed CFD simulations can aid in the understanding of melter behavior to increase efficiencies and reduce operational risks.

Presenting Author: Donna Guillen Idaho National Laboratory

Presenting Author Biography: Donna Post Guillen is the Group Lead for Materials Performance and Modeling in the Materials Science and Manufacturing Department at Idaho National Laboratory. Dr. Guillen has over 40 years of research engineering experience and has served as principal investigator/technical lead for numerous multidisciplinary projects encompassing waste heat recovery, combustion, heat exchangers, power conversion systems, nuclear reactor fuels and materials experiments, waste vitrification, and advanced manufacturing. Her core area of expertise is computational modeling of energy systems, materials, and thermal fluid systems. She is experienced with X-ray and neutron beamline experiments, computational methods, tools and software for data analysis, visualization, application development, machine learning and informatics, numerical simulation, and design optimization. As Principal Investigator/Technical Lead for the DOE Nuclear Science User Facility Program, she has engaged in irradiation testing of new materials and performed thermal analysis for nuclear reactor experiments. She actively mentors students, serves in a leadership capacity as well as routinely chairs and organizes technical meetings for professional societies (ANS, ASME, TMS), provides subject matter reviews for proposals and technical manuscripts, has published over 70 peer-reviewed journal articles, 150+ conference papers, received three Best Paper awards, authored numerous technical reports, and has written/edited several books and proceedings.

Authors:

Donna Guillen Idaho National Laboratory
Victor Leite Idaho National Laboratory
Pavel Ferkl Pacific Northwest National Laboratory
Pavel Hrma AttainX
Richard Pokorny University of Chemistry and Technology Prague
Albert Kruger U.S. Department of Energy