U(IV)是PUREX流程铀钚分离工艺中较为理想的还原剂。铂催化肼还原U(VI)制备U(IV)的方法具有料液组成简单、反应过程温和、反应流程短、所得产品液能直接应用等优点，但异相催化反应机理尚不清楚，难使反应处于精确可控状态。本项目研究肼在铂催化剂上分解产生初级自由基的种类及途径，以确定肼分子的断键方式，澄清肼在铂上产生初级自由基的反应历程；研究初级自由基与反应体系中U(VI)、肼、硝酸等的后续反应，考察生成的次级自由基产物及最终产物的种类与浓度，确定各反应体系下的反应链，得到不同反应物浓度对反应历程的影响；研究肼催化还原反应的热力学、动力学，并对反应过程的动力学进行模拟计算，进一步确定反应机理；以期直观地认识U(IV)制备的具体反应历程，了解反应特点，确定反应控制步骤，提高催化剂活性及选择性，为铀钚分离试剂U(IV)制备工艺的优化、减少副反应产生、工业化生产提供理论依据及技术支持。

U (IV) is a relative ideal reductant in uranium and plutonium separation stage in the PUREX process. U(IV) is produced by hydrazine reducting U(VI) with Platinum as catalyst, which has advantages of the simple material liquid composition , mild reaction process, short reaction process, and the liquid product can be directly applied. It has been long applied in the nuclear fuel reprocessing plant, but the reaction mechanism is unclear. This project will study the types of primary radicals and the producing way of hydrazine on platinum catalyst. And the purpose is to determine the free radicals reaction of hydrazine on platinum surface and the broken mode of the chemical bond of the hydrazine molecules, and to clarify the types of primary radicals. By investigating the subsequent reaction of the primary radicals and mediums in different concentrations of U (VI), hydrazine, nitric acid etc in reaction system, and examining the generated secondary free radical product,free radical kinds and the concentrations of final products, to determine the reaction chain under different systems, it can get the influence of different concentration of reactants on the reaction mechanism. The article will study reaction heat, dynamics of hydrazine catalytic reduction, and the analog computation is carried out based on the reaction kinetics of the reaction process to determine the reaction mechanism. Thus it can intuitively know the specific reaction mechanism of U (IV) preparation process, understand the characteristics of the reaction, determine the reaction controlling steps and it can be targeted to speed up the reaction rate of this controlling steps, improve the activity and selectivity of the catalyst, which can provide the theory basis and technical support for industrialized production and the optimization of preparation technology of uranium plutonium separation reagent U (IV) in process of spent fuel reprocessing and reducing side reactions.