TBP-HNO3萃取体系中U(Ⅳ)、Th(Ⅳ)和Pu(Ⅳ)第三相形成及计算机模拟研究进展

摘要

在PUREX或Thorex流程中,第三相的形成是一个实际问题,其形成不仅会影响U(Ⅳ)、Th(Ⅳ)和Pu(Ⅳ)的收率,还会影响工艺的正常运行.研究多集中在第三相的形成机理和影响因素上,发现四价锕系元素第三相的溶剂化物结构与正常溶剂化物结构并不相同;萃取剂结构与浓度、稀释剂结构与浓度、温度、平衡水相酸浓度和离子强度等为影响第三相形成的因素.在第三相基础数据的基础上建立了可以定量计算M(Ⅳ)形成三相的经验或半经验模型,模型大多使用萃取剂浓度、平衡水相酸度或平衡水相离子强度等关联得到,但尚未见到这些第三相数学模型在PUREX流程或Thorex流程模拟软件中应用,还需要进一步的研究.%Formation of third organic phase in PUREX or Thorex process is investigated under various conditions,because it may reduce the yield of Th(Ⅳ),U(Ⅳ)or Pu(Ⅳ), sometimes it may affect the normal operation of the process.In early period,the composition of the actinide(Ⅳ)tributyl phosphate solvate was assumed to be same in the unpartitioned organic phase and the formed third phase.But base on spectroscopy,the results indicate the presence of an extended solvate of M(Ⅳ).The effects of the temperature,the concentration of nitric acid and the extractant,the nature of diluent and the ionic strength of the aqueous phase on the formation of the third phase of M(Ⅳ)were investigated.Based on the mecha-nism studies,semi-empirical and empirical models of tetravalent actinide have been devel-oped,correlating various third phase characteristics of third formation of Th(Ⅳ),U(Ⅳ)or Pu(Ⅳ).But these models have not yet to be reported used in the simulation of the process.