双羟基脲与HNO_2的反应动力学及对Pu(Ⅲ)的稳定作用  

Reaction Kinetics of Dihydroxyurea With Nitrous Acid and Its Effect on Stabilizing Pu(Ⅲ)

作　　者：晏太红[1] 郑卫芳[1] 叶国安[1] 张宇[1] 鲜亮[1] 卞晓艳[1] 迪莹[1] 

机构地区：[1]中国原子能科学研究院放射化学研究所,北京102413

出　　处：《核化学与放射化学》2009年第2期65-71,共7页Journal of Nuclear and Radiochemistry

摘　　要：研究了HClO4和HNO3体系中双羟基脲(DHU)与HNO2的反应动力学。结果表明,HClO4和HNO3体系下DHU与HNO2的反应动力学速率方程式均为-dc(HNO2)/dt=k.c(HNO2)1.c(DHU)0.c(H+)-0.15,反应对DHU均呈零级。在HClO4体系下,θ=15℃,I=0.5 mol/kg时,反应速率常数k1=(2.37±0.04)mol0.15/(L0.15.min);在HNO3体系下,θ=10℃,I=0.5 mol/kg时,反应速率常数k2=(1.29±0.06)mol0.15/(L0.15.min)(n=8)。同时考察了反应温度对反应速率的影响,结果表明,随着温度的升高,反应速率均明显加快,HClO4和HNO3体系对应的反应活化能分别为68.2 kJ/mol和76.8 kJ/mol。在HClO4和HNO3体系中,随着离子强度的增加,氧化还原反应的表观速率常数k′均下降。过量的DHU在HNO3溶液中可以很好的稳定Pu(Ⅲ)48 h而不被氧化。Nitrous acid should be scavenged in the partitioning step of Purex process because it affects the valence of plutonium and some of other nuclides. Dihydroxyurea （DHU） was found to be a promising reductant to stabilize Pu（Ⅲ）. The reaction kinetics of DHU with nitrous acid was studied in HClO4 and HNO3 media. The reaction rate equation is expressed as -dc（HNO2）/dt= k. c（HNO2）^1·c（DHU）^0 · c（H＋）^-0.15. In HC104 and HNO3 media, the reaction rate constants are （2.37±0.04） mol^0.15/（L^0.15·min） at θ=10℃, I=0.5 mol/kg and （1.29±0.06） mol^0.15/（L^0.15 · min） （n=8） at θ=10℃, I=0. 5 mol/kg, respectively. The reaction rate constant decreased slightly with the increase in ion strength. The effect of temperature on the reaction rate was also studied and it was found that the reaction rate increased quickly with the increase in temperature. The reaction activation energies are 68.2 kJ/mol and 76.8 kJ/mol in HC104 and HNO3 media, respectively. In 0.5-3.0 mol/L nitric acid solutions, excess DHU can stabilize Pu （Ⅲ） well over 48 h.

关 键 词：双羟基脲 HNO2 反应动力学 Pu(Ⅲ) 

分 类 号：TL242.1[核科学技术—核燃料循环与材料]