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Passivation Effect of Metallic Uranium by Superitical Fluid CO2
Wang Qian,Meng Daqiao,Zhang Guangfeng,Xue Weidong,Zhang Li,Zhu Zhenghe*
Author NameAffiliationE-mail
Wang Qian China Academy of Engineering Physics, P.O.Box 919-71, Mianyang 621900  
Meng Daqiao China Academy of Engineering Physics, P.O.Box 919-71, Mianyang 621900  
Zhang Guangfeng China Academy of Engineering Physics, P.O.Box 919-71, Mianyang 621900  
Xue Weidong Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065  
Zhang Li Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065  
Zhu Zhenghe* Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 zhuxm@scu.edu.cn 
Abstract:
The present work is devoted to examine the passivation effect of metallic uraniu by supercritical fluid CO2, which is the most significant. The structure and thermodynamic properties of UC, C, UO2 and supercritical fluid CO2 have been calculated, based on which following simultaneous reactions have been examined using chemical equilibrium theory. The results indicate that the △G° for U(α)+CO2(g)UO2(s)+C(Graphite) reaction is -149.8~-632.0 kJ, △G° for 2U(α)+CO2(g)UO2(s)+UC(s) reaction is -725.1~-730.2 kJ, and both △G<0 and equilibrium closely approach products. It is also well known that the supercritical fluid is quite active in kinetics, and therefore the product compounds UC, C and UO2 would be quite stable. After the calculated molar tatio of UC, C and UO2, the stoichiometric ratio of elements is UC0.65±0.01O1.30±0.01, which would be useful for XPS observation.
Key words:  Uranium, Supercritical fluid CO2, Passivation
FundProject:
超临界CO2钝化金属铀的理论研究
王茜,蒙大桥,张广丰,薛卫东,张莉,朱正和*
摘要:
考察超临界CO2对金属铀表面的钝化作用.首先计算UC、 C、 UO2和超临界CO2的结构和热力学性质,基于这些性质,应用化学平衡原理计算,计算结果指出,反应U(α)+CO2(g)UO2(s)+C(Graphite)的△G°为-149.8~-632.0 kJ,反应2U(α)+CO2(g)UO2(s)+UC(s)的△G°为-725.1~-730.2 kJ,两者均远小于零,即△G<0,且平衡很接近产物一端UC、 C、 UO2.同时,已经熟知超临界流体的动力学性质极活泼,所以,产物UC、 C和UO2是很稳定的主要成分.根据所计算的产物分子比可以得到元素计量比为UC0.65±0.01O1.30±0.01,这显然不代表某种分子,但是,这对XPS分析很有用.
关键词:    超临界CO2  钝化作用
DOI:10.1088/1674-0068/18/2/157-160
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