WSRC-MS-2003-00595, Revision 0 CHARACTERIZATION AND PERFORMANCE OF FLUIDIZED BED STEAM REFORMING (FBSR) PRODUCT AS A FINAL WASTE FORM

A demonstration of Fluidized Bed Steam Reforming (FBSR) was recently completed on a Hanford Low Activity Waste (LAW) simulant. This technology produced stable mineral phases (feldspathoids) when co-fired with clay. The mineral phases are cage structured and were determined to retain anions such as SO4 as well as cations such as Re (simulant for Tc) in the mineral cages. The mineral phases are produced at moderate steam reformer operating temperatures between 650-750°C. The FBSR mineral waste form exhibited incongruent leaching characteristics during Product Consistency Testing (PCT or ASTM C1285). The radionuclides (Cs and Re as simulants for Cs and Tc) are released in significantly lower concentrations than Na. In addition, the Na release is less than the 2 g/m Hanford contract requirement for vitrified LAW. FBSR mineral waste forms are EPA regulatory compliant at the Universal Treatment Standard (UTS) making delisting an attractive option for this waste form. INTRODUCTION The Hanford LAW is a basic high Na molarity (~8.1M) sodium nitrate – sodium hydroxide solution that also contains significant amounts of sulfate, chloride, fluoride and organic compounds as well as certain heavy metals and radionuclides. LAW is the low activity salt supernate fraction of Hanford High Level Liquid Waste (HLLW). In December 2001, Fluiduized Bed Steam Reforming (FBSR), was investigated for stabilization of LAW waste by THOR Treatment Technologies (TTT) using the patented THermal Organic Reduction (THOR) process. This process, developed by Studsvik, utilizes pyrolysis/steam reforming to destroy both organics and nitrates/nitrites in the waste. The FBSR demonstrations were performed on ~150 gallons of a Hanford AN-107 LAW simulant simultaneously being used for a vitrification demonstration. The radionuclide Tc was simulated with Re while Cs was simulated with stable cesium (Cs). The non-radioactive AN-107 simulant of 8.1M Na was successfully tested in a 6-inch TTT pilot scale facility. Other demonstrations performed by TTT showed that LAW waste could be transformed into Na2CO3, NaAlO2, or Na2SiO3 feed material for the LAW Hanford melter (Table I). Addition of no solid coreactant yielded a sodium carbonate product. Sodium will combine with carbon dioxide in the reformer gases to provide a sodium carbonate product. The generation of sodium carbonate in this type of application has been known since the 1950s in fluid bed denitration systems [1]. Addition of an Al(OH)3 coreactant will provide an NaAlO2 product, addition of SiO2 will provide an Na2SiO3 product, while addition of clay will provide a final mineral waste form product (Table I). The latter has been shown to perform well as a final waste form [2,3]. Testing on Hanford LAW surrogates has shown that over 95% of the sulfur compounds, fluorides and chlorides in the waste feed react in the steam reformer with the clay co-reactant and become an integral part of the final mineral waste product structure [2]. Table I. THOR Pilot Scale Demonstrations with Simulated LAW Wastes