Evaluation of FP chemistry under sever accident conditions with focuses on the effects of BWR control material, 3; Thermodynamic study of gaseous CsBO by Knudsen effusion mass spectrometry

Nakajima, Kunihisa  ; Takai, Toshihide  ; Furukawa, Tomohiro  ; Osaka, Masahiko  

Gaseous cesium metaborate, CsBO(g), is predicted to be the main cesium vapor species, depending on temperature, in severe light water reactor accidents according to thermodynamic analysis, which treats chemical reactions between boron and cesium. But quality of the thermodynamic data of CsBO(g) used in this thermodynamic analysis is considered to be poor. Thus, Knudsen-effusion mass-spectrometric measurement of CsBO was performed to obtain reliable thermodynamic quantities of CsBO(g). The standard enthalpy values of formation of CsBO(g), (CsBO,g), were obtained by the 2nd law and the 3rd law treatments from measured vapor pressures and found to be -700.6 9.8kJ/mol and -698.0 10.6kJ/mol, respectively. These two values agree within the error limits and the evaluated thermodynamic data of CsBO(g) are considered to be reliable.