Structural and thermal properties of Cs-Fe-Si-O systems under LWR severe accident by DFT calculations

Miradji, F.; Suzuki, Chikashi ; Nakajima, Kunihisa  ; Osaka, Masahiko  

In the framework of FDNPS severe accident (SA), Cesium (Cs) retention phenomena are of high interest due to their impact on the decommissioning and dismantling work. Current SA analysis codes present large uncertainties in the estimation of Cs retention at reactor coolant system regions, due in part to the lack of knowledge in Cs chemisorption processes onto stainless steel (SS) surfaces. To improve and extend knowledge on Cs chemisorption mechanisms with SS, we investigated potential Cs-(Fe)-Si-O formed species by means of experimental and theoretical approaches. In this study, we will present the derivation of Cs-(Fe)-Si-O substances structural and thermodynamic properties from DFT calculations and the validation of developed computational methodology through comparisons with available literature data. In particular, the thermodynamic properties of newly characterized Cs chemisorbed species in our experimental tests are provided for the first time.