UO2芯块在硝酸溶液中的溶解反应动力学

Dissolution Kinetics of UO2 Pellets in Nitric Acid Solution

UO2芯块在硝酸溶液中溶解动力学参数数据较离散,研究了溶解过程中芯块表面积变化曲线,在芯块表面积定量基础上探究了芯块在硝酸溶液中的溶解反应动力学。根据溶解过程中芯块表面单位面积溶解速率计算结果,比较不同温度与酸度条件下单位面积溶解速率,获得了表观动力学参数。结果表明:UO2芯块在硝酸溶液中溶解,初始反应速率略慢(反应诱导期),之后反应加快并相对稳定(快速溶解期);在反应诱导期与快速溶解期,H+反应级数均为2.6级,反应活化能分别为49.75 kJ/mol和33.29 kJ/mol。

In view of the discreteness of dissolution kinetics parameters of UO2 pellets in nitric acid,the evolution of UO2 pellets surface area during dissolution was obtained.The dissolution kinetics were studied on the basis of quantitative surface area of pellets.The dissolution rate per unit area was calculated according to the measured surface area,and the apparent kinetic parameters were obtained by comparing the dissolution rates per unit area under different temperatures and acidity conditions.Results show that the rate of this reaction is slightly slow at the beginning(the inductive phase),and then enters a stage of slightly faster and relatively stable reaction period(the rapid dissolution phase).The reaction order of H+was 2.6 both in the inductive phase and the rapid dissolution phase.The activation energy of reaction in inductive phase and the rapid dissolution phase is 49.75 kJ/mol and 33.29 kJ/mol,respectively.