SAS4A analysis of CABRI experiments for validation of axial fuel expansion model

SAS4AによるCABRI試験を用いた軸伸び検証解析

石田 真也  ; 佐藤 一憲 

Ishida, Shinya; Sato, Ikken

Axial fuel expansion introduces negative reactivity and provides an inherently safe mechanism promptly responding the fuel heat-up; therefore it plays a key role in IP sequence. For the validation of the axial fuel expansion model with a computer code SAS4A, the analytical results were compared with the CABRI experimental data. It was firstly confirmed that the SAS4A model with a standard option for axial fuel expansion resulted in somewhat overestimation of fuel expansion for some experiments, which is caused by the particular axial gap enhanced during the preparation of the CABRI experiments. Although this effect is not expected in the real accident condition, one can get rid of this uncertainty introducing a conservative approach in which the cladding restricts the fuel column expansion. Secondly, this alternative option for fuel expansion model was adopted and it was confirmed that this method could give reasonable fuel expansion with a sufficiently conservative characteristic.