원전 중대사고 시 보조건물 내 작업자 선량평가를 위한 방사선 환경 분석

Abstract

In During severe accidents at nuclear power plants, field operations performed by workers in auxiliarybuildings play a critical role in accident mitigation. Quantitative evaluation of the radiation environment in these areasis essential for accurate worker dose assessment and radiation safety. In this study, five representative worker actionswere derived from the Severe Accident Management Guidelines (SAMG), and three representative severe accidentscenarios—LBLOCA, SBO, and LOFW—were selected. The MAAP5.06 code was used to calculate radiation sourceterms for nine major compartments in the auxiliary building, reflecting worker’s paths and action timelines. Airbornesource terms were evaluated for Xe and I, while deposited source terms were analyzed for Mo, I, Cs, and Te; Xenonand Iodine were chosen as representative nuclides. The analysis, performed for a time range of 0 to 90,000 secondsafter accident onset, showed that airborne Xenon concentrations were similar among scenarios, while depositedIodine levels varied significantly, with the highest values observed in the LOFW scenario. All scenarios exhibitedlower source terms in the basement (55 ft) compared to upper floors, and non-uniform spatial distributions acrosscompartments. The results highlight that the radiation environment within the auxiliary building exhibits distincttemporal and spatial variations depending on the accident scenario. The primary objective of this study is to generatecompartment-specific radiation source term data in a format directly applicable to high-fidelity dose assessmentcodes. The evaluated source terms are provided in units of kg · m−3 (airborne) and kg · m−2 (deposited), ensuringcompatibility with MCNP6 and Dose-Sim. These data serve as essential input for future worker dose simulationsand can support the development of an ALARA-based decision support system for radiation exposure prediction anddiagnosis during severe accidents.