Radiological Environmental Consequence Analysis of Hypothetical Severe Accidents at Nuclear Power Plants

원자력발전소 가상 중대사고시 방사선 환경영향 분석

Analysis of radiological environmental consequences for hypothetical severe accidents at Korean nuclear power plants (NPPs) was performed using radiological assessment system for consequence analysis (RASCAL) and hybrid single particle Lagrangian integrated trajectory (HYSPLIT) code. Through the benchmarking study of radiological source terms released to the atmosphere in case of Fukushima Daiichi NPP (FDNPP) accident, it was proved that the results of this study would fall within a reasonable range of the same order of magnitude compared with existing research results. Assuming a long-term station blackout (LTSBO) similar to FDNPP accident, we also analyzed the potential consequences of Shin Kori units 3 and unit 4 following postulated reactor core meltdown accidents which would lead to large releases of radioactive materials to the atmospheric environment and total source terms were estimated to be 4.1×10¹⁶ Bq. Korean regulatory standards of emergency management recommended immediate protective actions of sheltering-in-place and evacuation if the projected radiation doses to the population exceeded 10 mSv and 50 mSv in the first 2 days and 1 week after the accident, respectively. It was found that total effective dose equivalent (TEDE) ranged from 11 mSv at 4.83 km to 50 mSv at 1.61 km around Shin Kori NPPs and therefore urgent public protective actions should be implemented in case of an emergency.

본 연구에서는 국내 원자력발전소의 가상 중대사고시 RASCAL 및 HYSPLIT 코드를 사용해 방사선 환경영향분석을 수행하였다. 후쿠시마 사고와 벤치마킹 분석을 통해 대기로 유출된 방사선원항이 기존의 연구결과와 동일한 크기 자릿수로 합리적인 범위 내에 있음을 입증하였다. 또한 후쿠시마 사고와 유사한 장기전원상실사고를가정하여 신고리 3, 4호기의 노심용융에 따른 영향평가를 수행한 결과, 사고로 인해 대기환경으로 유출된 방사성물질의 양은 상당하였으며 총 방사선원항은 4.1×10¹⁶ Bq로 평가되었다. 국내 방사능방재 규제기준은 사고후 예상주민피폭선량이 2일에 10 mSv를 초과하면 옥내대피를, 1주일에 50 mSv를 초과하면 주민소개를 권고한다. 총유효선량당량은 신고리 원자력발전소로부터 반경 4.83 km에서 11 mSv, 1.61 km에서 50 mSv로 평가되었으며 비상시주민보호조치가 신속히 이행되어야 하는 것으로 확인되었다.