Evaluation of accident mitigation capability of passive core and containment cooling systems of i-SMR under representative LOCA and non-LOCA conditions

The global climate crisis has accelerated efforts to cut greenhouse gas emissions in the energy sector. While renewable energy faces limits in capacity and high costs, nuclear power offers a low-carbon, reliable baseload alternative and has been included in the EU Green Taxonomy since 2023 as a top option for achieving net-zero targets. Meeting heightened safety standards in nuclear power plants (NPPs) and rising electricity demand driven by AI has spurred strong interest in small modular reactors (SMRs) equipped with advanced passive safety systems. A standout example is Korea's innovative SMR (i-SMR), which delivers 170 MWe and is engineered to enhance safety by over 1000 times compared to traditional NPPs, with core damage frequency and early release frequency below 1.0E-09 and 1.0E-10 per module-year, respectively. Using the MELCOR code, this study evaluates the i-SMR's passive cooling systems under LOCA and non-LOCA conditions. The results confirm these systems can maintain reactor core and fuel integrity for 72 h post-accident without operator intervention, showcasing the high efficacy of the i-SMR's passive safety systems. • Developed the first of its kind MELCOR i-SMR input model to perform accident analyses. • Evaluated accident mitigation capabilities of passive safety systems (PSSs) of i-SMR. • Analyzed thermal-hydraulic characteristics during PSS activation under LOCA and non-LOCA conditions. • Nuclear fuel and reactor core remained intact solely through the operation of PSSs.