Thermodynamic Study of UO3(g), UO2(OH)2(g), UO2Cl2(g), and UO2F2(g)

Ebbinghaus, B B ; Krikorian, O H ; Fleming, D L

Lawrence Livermore National Laboratory

关键词: Oxidation;    Transpiration;    Oxygen;    Evaporation;    37 Inorganic, Organic, Physical And Analytical Chemistry;   

DOI  :  10.2172/15002517
RP-ID  :  UCRL-ID-150979
RP-ID  :  W-7405-ENG-48
RP-ID  :  15002517

美国|英语

来源: UNT Digital Library

【 摘 要 】

Using the transpiration method, the volatility of uranium oxide in the presence of oxygen and water vapor has been measured at temperatures ranging from 1173 to 1573 K and the volatility of uranium oxide in the presence of oxygen and chlorine has been measured at 1175 K. The major vapor species in the presence of oxygen and water vapor are found to be UO{sub 3}(g) and UO{sub 2}(0H){sub 2}(g). Third law treatment of the vaporization data yields {Delta}H{sub f}{sup o}(298) values of -790.52 {+-} 7.32 and -1199.94 {+-} 10.25 kJ/mol, respectively. The major vapor species in the presence of oxygen and chlorine is found to be UO{sub 2}Cl{sub 2}(g). Third law treatment of the vaporization data yields a {Delta}H{sub f}{sup o}(298) value of -1002.04 {+-} 3.26 kJ/mol. From an assessment of all the thermodynamic data available for UO{sub 3}(g), UO{sub 2}(OH){sub 2}(g), UO{sub 2}Cl{sub 2}(g), and UO{sub 2}F{sub 2}(g), the best {Delta}H{sub f{sup o}}(298) values for each of these species are calculated to be -796.74 {+-} 3.52, -1199.94 {+-} 10.25, -999.64 {+-} 2.40, and -1369.22 {+-} 2.87 kJ/mol, respectively. From these, the {Delta}H{sub f{sup o}} (298) values for UO{sub 2}ClOH(g), UO{sub 2}FOH(g), and UO{sub 2}FCl(g) are estimated to be -1099.79, -1284.58, and -1184.43 kJ/mol, respectively. The thermodynamic data for all the vapor species are then applied to conditions one might expect in a thermal oxidation processor for mixed waste to estimate the amount of uranium volatility.