Development of an evaluation methodology for fuel discharge in core disruptive accidents of sodium-cooled fast reactors

Kamiyama, Kenji  ; Tobita, Yoshiharu; Suzuki, Toru; Matsuba, Kenichi  

The purpose of the present study is to develop a methodology to evaluate fuel discharge through the control-rod guide tube (CRGT) during core-disruptive accidents (CDAs) of sodium-cooled fast reactors (SFRs) since fuel discharge will decrease the core reactivity and CRGTs have a potential to provide an effective discharge path. Fuel discharge contains multi-component fluid dynamics with phase changes, and, in the present study, the SFR safety analysis code SIMMER was utilized as a technical basis. First, dominant phenomena affecting fuel discharge through the CRGT are identified based on parametric calculations by SIMMER. Next, validations on the code models closely relating to these phenomena were carried out based on experimental data. It was shown that SIMMER with some model modifications could reproduce the experimental results appropriately. Through the present study, the evaluation methodology for the molten-fuel discharge through the CRGT was successfully developed.