Analysis of CABRI-BI1 Loss of Flow Experiment based on ISAA-Na

[Background]: Sodium boiling is a critical transient phenomenon prior to severe accidents in sodium-cooled fast reactors. Accurate prediction of the two-phase state and thermodynamic parameters of the coolant during sodium boiling is essential for sodium-cooled fast reactors accident analysis. [Purpose]: This paper aims to develop a core thermal-hydraulic model for the sodium-cooled fast reactor integrated analysis program ISAA-Na, based on the multi-bubble liquid slug assumption. [Methods]: The ISAA-Na code was used to simulate and analyze the loss-of-flow experiment CABRI-BI1 (Cœur à Haut Bûrnup Irradiation). [Results]: Comparison with experimental data shows that ISAA-Na provides more accurate predictions of coolant temperature and pressure prior to boiling compared to other codes such as SAS4A, ASTEC-Na, and SIMMER. However, after the onset of boiling, overestimations of bubble growth rate and two-phase interface movement were observed due to the lack of fuel melting and cladding failure models. [Conclusions]: Overall, the application of the multi-bubble liquid slug boiling model in ISAA-Na for the analysis of the CABRI-BI1 experiment is deemed reasonable and reliable.