In general, after the decommissioning of nuclear facilities, buildings on the site can be demolished or reused. The NSSC (Nuclear Safety and Security Commission) Notice No. 2021-11 suggests that when reusing the building on the decommissioning site, a safety assessment should be performed to confirm the effect of residual radioactivity. However, in Korea, there are currently no decommissioning experiences of nuclear power plants, and the experiences of building reuse safety assessment are also insufficient. Therefore, in this study, we analyzed the foreign cases of building reuse safety assessment after decommissioning of nuclear facilities. In this study, we investigated the Yankee Rowe nuclear power plant, Rancho Seco nuclear power plant, and Hematite fuel cycle facility. For each case, the source term, exposure scenario, exposure pathway, input parameter, and building DCGLs were analyzed. In the case of source term, each facility selected 9~26 radionuclides according to the characteristics of facilities. In the case of exposure scenario, building occupancy scenario which individuals occupy in reusing buildings was selected for all cases. Additionally, Rancho Seco also selected building renovation scenario for maintenance of building. All facilities selected 5 exposure pathways, 1) external exposure directly from a source, 2) external exposure by air submersion, 3) external exposure by deposited on the floor and wall, 4) internal exposure by inhalation, and 5) internal exposure by inadvertent ingestion. For the assessment, we used RESRAD-BUILD code for deriving building DCGLs. Input parameters are classified into building parameter, receptor parameter, and source parameter. Building parameter includes compartment height and area, receptor parameter includes indoor occupancy fraction, ingestion rate, and inhalation rate, and source parameter includes source thickness and density. The input parameters were differently selected according to the characteristics of each nuclear facility. Finally, they derived building DCGLs based on the selected source term, exposure scenario, exposure pathway, and input parameters. As a result, it was found that the maximum DCGL was 1.40×108 dpm/100 cm2, 1.30×107 dpm/100 cm2, and 1.41×109 dpm/100 cm2 for Yankee Rowe nuclear power plant, Rancho Seco nuclear power plant, and Hematite fuel cycle facility, respectively. In this study, we investigated the case of building reuse safety assessment after decommissioning of the Yankee Rowe nuclear power Plant, Rancho Seco nuclear power plant, and Hematite fuel cycle facility. Source terms, exposure scenarios, exposure pathways, input parameters, and building DCGLs were analyzed, and they were found to be different depending on the characteristics of the building. This study is expected to be used in the future building reuse safety assessment after decommissioning of domestic nuclear power plants. This work was

The design life of the radioactive waste carrier, the CHEONG JEONG NURI, is in the year 2034, when the decommissioning of Kori Unit 1 is expected. As only IP-2 type transport containers (7.5- tons, 1.6 m (W) × 3.4 m (L) × 1.2 m (H)) can be loaded onto the CHEONG-JEONG-NURI, the radioactive decommissioning waste (RDW) transport containers neither of 35-tons maximum weight nor ISO type can be accommodated. Accordingly, either a new vessel (NV) to replace the CHEONGJEONG- NURI or a change in the loading dock design of the CHEONG-JEONG-NURI is required. In this study, the necessity of building a NV capable of accommodating the issued containers above is analyzed focusing, (1) the estimated building and operating costs of the NV, and (2) the economic feasibility of the NV ‘s RDW transportation scenarios. Among bulk carriers, the CHEONG-JEONG-NURI was designed as handy-size ship type. It is operated reflecting various design requirements to satisfy the domestic/international legal requirements. To estimate the cost of the NV, the same vessel type and design criteria of the CHEONG-JEONGNURI were considered. The shipping price information of the Korea Ocean Business Corporation, as of August 2022, the building cost of bulk carrier Handysize (building NV type) is about USD 30 million. Considering domestic/overseas variables, such as future labor costs, international inflation, interest rate hike, etc., the building costs are expected to continuously rise. Furthermore, vessel operation costs of crew labor, vessel, fuel, and insurance are incurred separately. Due to the increase in oil price, and wages of special positions, such as general seafarers and radiation safety managers, the NV’s operating cost is expected to be about KRW 3.8 billion every year, which is about KRW 1.1 billion higher than that of the CHEONG-JEONG-NURI. The expected total cost of building and operating the NV is about KRW 65 billion. Assuming the repayment period of the NV building cost is the same as that of the CHEONG-JEONG-NURI building cost reimbursement agency and analyzing the economic feasibility of the transport scenario of the NV built by adding up about KRW 3.8 billion of the operating cost, cost about KRW 880 million per voyage of the NV built is expected, which being KRW 620 million more than the current cost (KRW 260 million) per trip of the CHEONG-JEONG-NURI. Therefore, transporting the RDW to the disposal facility through sustainable use of the CHEONGJEONG- NURI (considering design life extension and design change) is evaluated as more appropriate than building NV.

한국원자력환경공단은 처분시설 내 1단계 인수·저장구역의 인수검사 공간 및 드럼 취급 공간 부족에 대한 문제를 해결하기 위하여 방폐물검사건물을 건설하여 저장·처리능력을 확충할 예정이다. 본 연구에서는 MCNP 코드를 이용하여 방폐물검사 건물 내 저장구역에서 취급하는 해체 방사성폐기물 대상 신형처분용기를 대상으로 작업종사자의 피폭선량을 평가하였다. 평가결과, 시설 내 저장 가능한 최대 용기 개수(304개)와 방사선작업에 대한 연간 예상 작업시간(약 306시간)에 대하여 연간 집단선량은 총 84.8 man-mSv로 계산되었다. 시설 내 총 304개의 신형처분용기(소형/중형 타입)가 저장 완료된 시점에서 인수검사, 처분검사를 위한 작업종사자의 투입인력은 총 25명, 작업종사자 당 예상피폭선량은 연평균 3.39 mSv로 산출 되었다. 소형용기 취급 시 작업종사자의 고방사선량 작업에 따른 작업효율과 방사선적 안전성 확보를 위해서는 콘크리트 라이너의 두께를 증가시키는 추가적인 차폐가 필요할 것으로 평가되었다. 향후 본 연구를 바탕으로 실측기반의 해체폐기 물의 선원항과 특성을 활용하여 방사선작업 당 작업시간 및 투입인력을 산출함으로써 작업종사자의 최적의 방사선작업조건을 도출할 수 있을 것으로 사료된다.