For safe and successful decommissioning, it is one of the most important procedures that establishing the goal and complying with regulations of which final status of decommissioned site and building. The dose criteria for cyclotron facilities should be established and applied to reuse the site and building, since building and component of a cyclotron facility have been activated by incident secondary neutrons from radioactive isotope processes (e.g. 18O(p,n)18F, etc.). Furthermore, appropriate approaches should be applied to demonstrate compliance with the dose criteria for reliability of reuse. It is of noted that U.S. NRC (Nuclear Regulatory Commission) has confirmed that the residual radioactivity which distinguishable from background radiation results in a TEDE (Total Effective Dose Equivalent) does not exceed 25 mrem (0.25 mSv) per year as radiological criteria for unrestricted use of not only nuclear power plants but also cyclotron facilities referred to 10 CFR Part 20.1402. In addition, U.S. NRC noted the two approaches (i.e. dose assessment methods and, DCGL and final status surveys) which can be applied for demonstrating compliance with the dose criteria of 10 CFR Part 20 and recommended DCGL and FSS approach based on advantages and disadvantages of the two approaches. In order to using DCGL and FSS approach, U.S. NRC suggested screening approach; using DandD Version 2 which assesses TEDE under ICRP 28 and site-specific approach; using all models or computational codes which approved by NRC staff. There are several foreign cases that release of cyclotron facilities after decommissioning (i.e. U.S. and Japan). U.S., for examples, there are two DCGL approach cases and one dose modeling case based on 25 mrem per year same as reactor facilities. The dose modeling case, however, which may not be really used in Korea because of its low applicability. On the other hand, Japan case did not establish any radiological criteria for site and building reuse such as DCGL and just confirm “no more contamination” which is all residual radioactivity is lower than MDC based on real survey. Japan case also may not be used in Korea since criteria of “no more contamination” is not clear and hard to apply for all sites. Considering regulations and criteria for site release and reuse in Korea, this study aims to suggest radiological criteria and the demonstration approach of compliance for decommissioning of cyclotron facilities based on Nuclear Safety Acts and NSSC notices.

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

2002년 한일월드컵의 성공적 개최로 인한 축구 열풍으로, 인조잔디구장 조성 붐이 형성되어 급격하게 확대되기 시작한 인조잔디시장은 교육부와 국민체육진흥공단의 생활체육 및 체육시설의 선진화 방안에 따른 인조잔디 조성계획으로 지자체 및 학교 등 공공기관이 수요가 보태지면서 가히 폭발적으로 성장하게 되었다. 인조잔디의 사용연한은 보통 7~8년으로 알려져 있으나, 이용이 빈번한 학교운동장, 공공체육 시설의 경우 평균 3~5년으로 짧은 편이다. 잔디파일의 경우 시간이 지남에 따라 물리적 마모 및 충격에 의해 열화가 진행되며, 파일의 탈락 및 인장강도, 인발력 저하, 고무분말 노출로 인한 분진 발생의 원인이 된다. 인조잔디가 깔린 학교는 전국에 1,580여 곳이며, 이 가운데 200여 곳(12.7%)은 사용연한이 다 됐거나 지났으며, 사용한 지 5년이 넘어 노후된 곳도 613곳(38.8%)이나 되어 폐기 인조잔디 처리가 시급한 문제로 떠오르고 있다. 국내 처리방법은 폐기 인조잔디 발생 시 사업장 폐기물로서 위탁, 소각 후 매립하고 있으며, 소각 후 매립 처분에 있어 대부분의 인조잔디와 충전재(고무분말, 규사)를 구분하지 않고 일괄 소각 후 매립하고 있어 자원의 낭비와 자연환경의 파괴가 우려된다. 이에 본 연구에서는 폐기 인조잔디 충전재의 0.5mm이하 미분쇄 가공을통한 TPV용 소재 개발을 위한 연구를 진행하였으며, 원자재 공급업체와 중가 가공처리업체, 최종 제품 수요업체, 총괄 관리기관 간의 업무분장을 통하여 자원 재활용 네트워크를 구축하였다.