Validation of ISAA-Na Code for Sodium-Cooled Fast Reactors: CABRI-BI1, AGS0, and E7 Experiments

Accurate transient behavior modeling is crucial for assessing the safety of sodium-cooled fast reactors (SFRs) . This study validates the ISAA-Na code through simulations of the CABRI-BI1, AGS0, and E7 experiments. The CABRI-BI1 experiment, focused on sodium boiling, was simulated using a multi-bubble slug flow model. Results showed that ISAA-Na more accurately predicted coolant temperature and pressure prior to boiling than SAS4A, ASTEC-Na, and SIMMER. In the CABRI-E7 experiment, ISAA-Na’s cladding failure model was tested under transient overpower (TOP) conditions. ISAA-Na’s results closely matched experimental data and other codes, successfully predicting fission gas release, coolant temperature, and cladding failure timing and location. The CABRI-AGS0 experiment further examined fuel pin behavior under TOP conditions. ISAA-Na accurately captured fission gas release, temperature, and fuel melting radius predictions. Overall, ISAA-Na demonstrates strong potential for SFR transient analysis, though further refinement in phase transition modeling is needed. This validation provides valuable insights into ISAA-Na’s capability to enhance SFR safety assessments.