Riley Brian J, Chong Saehwa, Lonergan Charmayne E
Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
ACS Omega. 2021 Nov 16;6(47):32239-32252. doi: 10.1021/acsomega.1c05065. eCollection 2021 Nov 30.
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 (NHHPO or ADP) at temperatures up to 600 °C to produce NHCl as a byproduct. The benefits of removing the Cl from these salts include Cl recovery from Cl-based MSR salts, formation of UCl from the NHCl, 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 NHCl 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 NHCl condensation on a four-piece fused quartz off-gas system. Both ADP and NHCl decomposition reactions include the production of NH and acids (i.e., HPO and HCl, respectively), so careful temperature control is needed during the ADP-salt reactions to maximize the NHCl production and minimize NHCl decomposition. In two sets of experiments run in the generation-1 and generation-2 apparatuses, NHCl 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 NHCl were performed to assess the temperatures of the reactions and identify off-gas products.
本文描述了一种用于从电化学后处理产生的基于氯化物盐的核废料和/或基于氯化物的熔盐反应堆（MSR）中去除氯的装置，该装置通过在高达600°C的温度下使盐与磷酸二氢铵（NH₄H₂PO₄或ADP）反应进行脱氯，以产生副产物NH₄Cl。从这些盐中去除Cl的好处包括从基于Cl的MSR盐中回收Cl、由NH₄Cl形成UCl，以及从盐中去除Cl并将盐阳离子转化为氧化物，以便固定在化学耐久性的磷酸铁废物形式中。这种第二代系统是对第一代系统的改进，提供了扩大盐通量以及回收NH₄Cl的方法。第二代系统包括一个五区炉，因此可以调整四区梯度炉的温度，以控制NH₄Cl在四件套熔融石英废气系统上的冷凝位置。ADP和NH₄Cl的分解反应都包括产生NH₃和酸（即分别为H₃PO₄和HCl），因此在ADP与盐的反应过程中需要仔细控制温度，以最大限度地提高NH₄Cl的产量并最小化NH₄Cl的分解。在第一代和第二代装置中进行的两组实验中，新系统的NH₄Cl产率比原始原型系统高≥5.5倍，且批量可以高≥2.5倍。此外，还进行了一些评估ADP + KCl反应以及纯NH₄Cl分解的热力学实验，以评估反应温度并确定废气产物。
