后处理厂硝酸回收及放射性液体最小化的蒸发浓缩技术

Technology of Concentration by Evaporation for Recycling of Nitric Acid Solution and Reduction of Radioactivity Discharge in the Reprocessing of Nuclear Fuel

综述了蒸发浓缩工艺在后处理厂中的应用,其主要是用于硝酸和水的循环复用及放射性废液体积的最小化。主要在以下几个方面应用:第一,后处理过程产生的1AW、2AW和2DW废液硝酸浓度均较高,这些废液的蒸发浓缩过程中,为了减小蒸发器的腐蚀,外加还原剂脱硝以控制硝酸浓度低于3mol/L、溶液温度低于100℃;第二,具有较高硝酸浓度的废液是草酸钚沉淀母液,其蒸发浓缩过程中不仅需要脱硝,还需要破坏溶液中的草酸根;第三,一些料液如1CU、2EU和2BP,硝酸浓度不高,可直接进行蒸发浓缩,无需脱硝。最后蒸发浓缩还可以处理后处理厂在启动、停车、去污、故障时产生的各种设计外的溶液。基于以上应用,蒸发浓缩技术被认为是简化和优化后处理厂的设计和操作,保证后处理厂灵活高效运行的重要技术。

The application of concentration by evaporation used nuclear fuel reprocessing plant has been summarized in this article. A conclusion was drawn that concentration by evaporation is a key technology in reprocessing plant which is mainly used in recycling of nitric acid, water and reduction of radioactivity discharge. The main applications are listed as follows. The liquid releasing from extraction units, such as 1AW, 2AW and 2DW, is high concentration of nitric acid during the concentration by evaporation of them so denitration with addition of reductant is necessary to remain the concentration of HNO3 below 3mol/L and temperature below 100 ℃ and avoid corrosion of the evaporator. Another liquid of the same high concentration HNO3 is the mother liquor from plutonium oxalate precipitation process and the destruction of oxalic acid should he an important issue besides the denitration during concentration by evaporation. Some liquids with low HNO3 concentration, for example, 1CU, 2EU and 2BP, and great variety of solutions generated from the startup, shutdown and abnormal operation also need to be concentrated by evaporation. Based on the analysis, it is found that concentration by evaporation can simplify and optimize the design and operation of reprocessing plant for its effective decontamination, high operation flexibility.