A Scenario-Driven Stability and Radiological Dose Evaluation for Human Exposure Resulting from Spent Nuclear Fuel Storage Facility Beyond Design-Basis Accident

This study quantitatively evaluates the radiological safety of a wet spent nuclear fuel (SNF) storage facility under a beyond design-basis accident scenario and examines the impact of key uncertainties. An exponential decay heat model based on operational data from Shin-Kori Units 1 and 2 and radionuclide inventories from the International Atomic Energy Agency’s IAEA TECDOC-1343 was employed. A 20-day loss of cooling with continuous evaporation was simulated using a GoldSim compartment model to estimate airborne radionuclide transport and resulting effective doses. Sensitivity analyses were conducted on boundary distance, restoration period, and atmospheric removal fraction. At the controlled area boundary (100 m), the cumulative effective dose was 11.46 mSv, equal to 23% of the 50 mSv/year limit in 10 CFR 72.106. Inhalation dominated exposure, exceeding external dose by a factor of ~3.3 × 104. Sensitivity results showed boundary distance and removal fraction as primary drivers, with doses ranging from 123.1 mSv at 10 m to 0.18 mSv at 1000 m and from 97.7 mSv at 5%/day removal to 1.16 mSv at 500%/day. These findings confirm compliance under conservative assumptions and highlight the importance of rapid recovery actions, adequate buffer zones, and meteorological considerations for robust SNF storage safety.