Fluidized Bed Steam Reformed (FBSR) Mineral Waste Forms: Characterization and Durability Testing
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Fluidized Bed Steam Reformed (FBSR) Mineral Waste Forms: Characterization and Durability Testing Carol M. Jantzen, Troy H. Lorier, John M. Pareizs, and James C. Marra Savannah River National Laboratory, Aiken, SC, 29803 ABSTRACT Fluidized Bed Steam Reforming (FBSR) is being considered as a mineralizing technology for the immobilization of a wide variety of wastes that are high in organics, nitrates-nitrites, halides, and/or sulfates. These wastes include the decontaminated High Level Waste (HLW) supernates referred to as low activity waste (LAW) at Department of Energy (DOE) sites in the United States and waste streams that may be generated by the advanced nuclear fuel cycle flowsheets that are being considered by the Global Nuclear Energy Partnership (GNEP) initiative. The organics are pyrolyzed into CO2 and steam in the absence of air. The FBSR mineral waste form is a granular but can subsequently be made into a monolith for disposal if necessary. The waste form is a multiphase mineral assemblage of Na-Al-Si (NAS) feldspathoid minerals (sodalite, nosean, and nepheline) with cage and ring structures that sequester radionuclides like Tc-99 and Cs-137 and anions such as SO4, I, F, and Cl. Iron bearing spinel minerals are also formed and these phases stabilize Resource Conservation and Recovery Act (RCRA) hazardous species such as Cr and Ni. Dissolution rates (η) and activation energies of dissolution are parameters needed for Performance Assessments (PA) to be completed on the FBSR mineral waste form. These parameters are defined in this study by Single Pass Flow Through (SPFT) testing. The dissolution rate (η) and the activation energies for dissolution calculated in this study agree with the available rate and activation energy data for natural single crystal nepheline. INTRODUCTION Fluidized Bed Steam Reforming (FBSR) is being considered as a potential technology for the immobilization of a wide variety of radioactive wastes. Studsvik built and tested a commercial FBSR Processing Facility in Erwin, TN, which began commercial operations in 1999 [1,2]. The Erwin facility employs the THermal Organic Reduction (THORsm) process, which utilizes the steam reforming technology to pyrolyze Cs-137 and Co-60 organic resins from commercial nuclear facilities. The reforming process is effective in pyrolizing organics and separating sulfur and halogens from organic waste materials at moderate temperatures (650-750∞C). The FBSR process is not combustion and is Clean Air Act (CAA) compliant. It has also been shown to be Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) compliant for Hg, Cl, CO, total hydrocarbons, and heavy metals.Of special relevance is the capability of the THORsm technology to convert nitrates to nitrogen and sodium salts to sodium compounds that are suitable for direct disposal and/or subsequent vitrification. If clay is added during processing a ìmineralizedî granular waste form is produced that is composed of various Na-Al-Si (NAS) feldspathoid minerals with cage and
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