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The Idaho National Engineering and Environmental Laboratory (INEEL) is considering several optional processes for disposal of liquid sodium-bearing waste. During fiscal year 2002, immobilization-related research included of grout formulation development for sodium-bearing waste, absorption of the waste on silica gel, and off-gas system mercury collection and breakthrough using activated carbon. Experimental results indicate that sodium-bearing waste can be immobilized in grout at 70 weight percent and onto silica gel at 74 weight percent. Furthermore, a loading of 11 weight percent mercury in sulfur-impregnated activated carbon was achieved with 99.8% off-gas mercury removal efficiency.iv v EXECUTIVE SUMMARYThe Idaho National Engineering and Environmental Laboratory, specifically the Idaho Nuclear Technology and Engineering Center (INTEC) High-Level Waste Program, is to prepare the liquid sodium-bearing waste and calcined solids for eventual disposal. Several alternative treatment processes and disposal paths have been explored for these wastes. This report discusses research conducted on three process options: grouting of sodium-bearing waste following cesium removal, immobilization of sodium-bearing waste on silica gel following cesium removal, and use of activated carbon for mercury removal in the calciner or steam reformer off-gas system.During this fiscal year, the option of grouting sodium-bearing (SBW) waste was revisited to ensure the processes were still viable based on the latest flow sheets and projected SBW compositions. It was determined that the grout formulation for 70 weight percent continued to be satisfactory. New work was started for grouting of nitric acid such as that from the Liquid Effluent Treatment and Disposal Facility. Initial findings showed that 12 molar nitric acid can be grouted at 35 weight percent.Research continued on the absorption of SBW on silica gel. The process provides a simple method of solidifying the SBW for transportation or disposal. If the SBW is placed on silica gel at ambient temperatures, waste loadings of 74 weight percent can be achieved with a single addition. If the SBW and silica gel are heated more moisture and acid are driven off and waste loadings of 90 weight percent were found.If thermal methods are pursued for SBW treatment, it is proposed to use activated carbon to control mercury release in the off-gas systems. The activated carbon bed's mercury removal efficiency and breakthrough loading for the New Waste Calciner Facility were researched this fiscal year. It was found that a breakthrough loading of 11 weight percent and a removal efficiency of up to 99.8% were achievable. vi vii NOMENCLATURE Alkaline GroutA grout formulation where the waste is rendered basic (pH > 12) and mixed with a 9:1 blend of blast furnace slag and portland cement.

SUMMARYRadioactive, acidic waste stored at the Idaho Nuclear Technology and Engineering Center (INTEC) have been previously converted into a dry, granular solid at the New Waste Calcining Facility (NWCF). As an alternative to calcination, direct vitrification of the waste, as well as the calcined solids in an Idaho Waste Vitrification Facility (IWVF) is being considered to prepare the waste for final disposal in a federal repository. The remaining waste to be processed is Sodium-Bearing Waste (SBW).Off-gas monitoring during NWCF operations have indicated that future mercury emissions may exceed the proposed Maximum Achievable Control Technology (MACT) limit of 130 ug/dscm (micrograms/dry standard cubic meter) @ 7% O 2 for existing Hazardous Waste Combustors (HWC) if modifications are not made. Carbon monoxide and hydrocarbon emissions may also exceed the MACT limits. Off-gas models have predicted that mercury levels in the off-gas from SBW vitrification will exceed the proposed MACT limit of 45 ug/dscm @ 7% O 2 for new HWCs.Options to enable the NWCF to meet the MACT limits included construction of a MACT Compliance Facility (MCF), including a Noxidizer for NO x removal, or upgrading the NWCF by installing a multi-sieved wet scrubber for mercury removal. Both options included continuous removal of mercury from the scrubber blowdown by electrochemical reduction, followed by an activated carbon polishing bed. In the NWCF upgrade option, the carbon bed was also to be used for removal of products of incomplete combustion. Thus, studies of the mercury removal efficiency of activated carbon were initiated to support the above-mentioned options. These studies indicated that Mersorb , a sulfur-impregnated carbon manufactured by Nucon International, was highly effective (>99% removal) in removing both elemental ( The test results obtained indicated that Mersorb may have potential for removing a sufficient amount of mercury from SBW vitrification off-gas to enable compliance with the MACT limit. No negative short-term effects of test gas components on mercury removal efficiency were apparent. Future recommended studies include small bed (1cm. diameter) tests to determine long-term effects of SBW vitrification off-gas components on HgCl 2 and Hg o removal efficiency. Also recommended are breakthrough capacity and bed size optimization studies with a larger test bed to determine maximum removal efficiency, and obtain scale-up data, which can be used to design a carbon adsorption bed for a pilot-scale melter.v