GOTHIC and MELCOR benchmarking of the CNL strong condensation containment apparatus experiments

Abstract

Understanding severe accident behaviour in water-cooled small modular reactors is crucial for their deployment, as well as having qualified software tools for safety analysis. A model benchmarking exercise was conducted where predictions from the software tools GOTHIC and MELCOR were compared against past experiments from the Strong Condensation Containment Apparatus (SCCA). Key phenomena that can be expected in small modular reactor (SMR) containments, given their small size and external passive water cooling, are explored, including how well the codes replicate stratification between a hot upper layer and a cooler under layer. This overall thermalhydraulics behaviour impacts other important phenomena, like heat transfer and aerosol deposition. MELCOR, an integrated severe accident code, and GOTHIC, a thermalhydraulic and containment code, were used in benchmarking activities, wherein the experimental results were compared to their simulation results. The findings demonstrated MELCOR’s capabilities to simulate the SCCA experiments and GOTHIC’s strength in predicting multiphase flow and thermalhydraulics in containment and cooling systems. In addition, the benchmark comparisons provided new insights toward modelling experiments with these codes as well as the behaviour observed in the SCCA experiment. These findings will guide accident management and emergency preparedness requirements for SMRs.