Dechlorination Apparatus for Treating Chloride Salt Wastes: System Evaluation and Scale-Up

[Image: see text] This paper describes an apparatus used to remove chlorine from chloride salt-based nuclear wastes from electrochemical reprocessing and/or chloride-based molten salt reactors (MSRs) through dechlorination by reacting the salts with ammonium dihydrogen phosphate (NH(4)H(2)PO(4) or ADP) at temperatures up to 600 °C to produce NH(4)Cl as a byproduct. The benefits of removing the Cl from these salts include (37)Cl recovery from Cl-based MSR salts, formation of UCl(3) from the NH(4)Cl, as well as removal of Cl from the salts and conversion of the salt cations to oxides to allow for immobilization in a chemically durable iron phosphate waste form. This generation-2 system is an improvement over the generation-1 system and provides a means for scaling up salt throughput as well as NH(4)Cl recovery. The generation-2 system includes a five-zone furnace so the temperature of the four-zone gradient furnace can be tailored to control the location of NH(4)Cl condensation on a four-piece fused quartz off-gas system. Both ADP and NH(4)Cl decomposition reactions include the production of NH(3) and acids (i.e., H(3)PO(4) and HCl, respectively), so careful temperature control is needed during the ADP-salt reactions to maximize the NH(4)Cl production and minimize NH(4)Cl decomposition. In two sets of experiments run in the generation-1 and generation-2 apparatuses, NH(4)Cl yields were ≥5.5-fold higher for the new system compared to the original prototype system and the batch sizes can be ≥2.5-fold higher. In addition, some thermodynamic experiments evaluating the reactions of ADP + KCl as well as decomposition of pure NH(4)Cl were performed to assess the temperatures of the reactions and identify off-gas products.