The cyclotron is an apparatus used for the production of radioactive isotopes through nuclear reactions, resulting in the inevitable emission of neutrons. Consequently, surrounding components become activated. The purpose of this study was to investigate the radiological characteristics of Havar foil, a periodic replacement part of the Targetry system. In this study, radioactivity and radiation dose were calculated based on the time of Havar foil replacement and equipment dismantling. The time to dismantle the equipment was set at one year after the equipment was shut down, based on the recently used 1g of Havar foil. All simulations were performed using the FLUKA program. First, in the simulation results, 11 elements (Re, W, Tc, Nb, Cu, Ni, Co, Fe, Mn, Cr, V) were converted into 36 radioisotopes by activation based on the replacement period. Based on radioactivity levels, major isotopes included 52Mn (77.63%), 56Co (13.36%), 96Tc (2.4%), and 95Tc (1.80%). Based on radiation dose rates, 52Mn (82.66%) and 56Co (13.45%) exhibited the highest levels. Furthermore, the dose rates at distances of 10 cm, 50 cm, and 100 cm were found to be 1.36E+1 mSv/hr, 2.24E+00 mSv/hr, and 8.80E-01 mSv/hr, respectively. Second, as of the time the equipment was dismantled, 20 radioactive isotopes of 10 elements, excluding short-lived nuclides, were generated. In terms of radioactivity, 56Co (45.83%), 55Fe (19.73%), 57Co (14.48%), and 54Mn (13.50%) were prominent. Regarding radiation dose rates, 56Co (92%) and 54Mn (7.32%) exhibited higher levels. Dose rates at distances of 10 cm, 50 cm, and 100 cm were calculated at 5.31E-01 mSv/hr, 8.80E-02 mSv/hr, and 3.47 E-02 mSv/hr, respectively. Third, according to the radioactive waste classification standards in the replacement and decommissioning stages, Havar foil was predicted to be low-level radioactive waste in terms of radioactivity. In addition, it was derived that a cooling period of approximately 12 years is necessary to satisfy the allowable dose for clearance level waste. In conclusion, Havar foil, which is periodically generated as radioactive waste, can cause radiation exposure to replacement workers. Therefore, special and careful management is required for the Havar foil of the cyclotron.

Kori and Wolsong unit 1 were permanently shutdown in 2017 and 2019, respectively. During the decommissioning of a nuclear power plant, various types and levels of decommissioning waste will be generated sporadically in many areas in a relatively short period of time, so safe management of decommissioning waste is expected to emerge as a very important issue in the future. Since Korea has no experience in decommissioning nuclear power plants, radionuclides added by abnormal routes or errors in data can be identified through the list of expected nuclides and radioactivity data during decommissioning by analyzing cases of overseas nuclear power plants decommissioning. Therefore, it is expected that safety information of nuclear power plants in the United States (i.e. all information related to safety, such as radioactive waste characteristics and accident or decommissioning information at nuclear power plants) can be utilized when decommissioning Korea nuclear power plants. Therefore, in this study, the characteristics of solid radioactive waste were analyzed by collecting solid radioactive waste data during operation and after permanent shutdown of nine PWR nuclear power plants in the United States, and the correlation between the characteristics data of solid radioactive waste was analyzed. However, in the case of Korea, only data from the United States were analyzed because there was no data for each radionuclide that were disclosed when disposing of radioactive waste in LILW repository and there was no nuclear power plant that had been decommissioned. Correlation analysis of solid radioactive waste was performed by linking radioactivity of radionuclides, volume of waste, and total radioactivity data based on decommissioning work and accident data after permanent shutdown or during operation. The correlation analysis of total radioactivity, volume, and radioactivity of each nuclide of solid radioactive waste during operation and after permanent shutdown was performed using XLSTAT, an Excel add-in software, for carrying out Mann-Kendall Test and estimating Sen’s slope. Trends during operation and after permanent shutdown were compared and the effects of specific events or tasks were analyzed. This study is expected to be utilized as basic data related to safety management of decommissioning Korea nuclear power plants in future.

생활주변방사선안전관리법 도입에 따라 재활용하지 못하는 공정부산물의 안전관리를 위해서는 방사선적 안전성 확보가 필 수적이다. 이를 위해서 처분대상 공정부산물 특성화 자료 수집 및 분석, 처분방법과 처분시설의 조사 및 분석, 처분시설의 운 영으로 인한 방사선적 안전성평가 방법론 정립과 도구 확보, 주요 입력자료들의 안전성에 미치는 영향 파악 등이 필요하다. 이를 통하여 매립과 같은 참조 처분방법을 선정하고 피폭선량과 인체보건 리스크 평가를 통하여 공정부산물 처분에 따른 방 사선적 안전성 확보를 위한 절차 및 기준마련을 위한 기술적 근거를 확보할 필요가 있다. 본 연구에서는 공정부산물 처분방 법과 공정부산물 처분시설에 대한 국내외 현황 조사 및 분석과 국내외 주요 산업별 처분대상 공정부산물 특성화 자료 수집 및 분석을 수행하였다. 이를 바탕으로 주요 공정부산물 특성에 따른 관리방안과 매립 처분시설에 대한 개념설계를 제안하였 다. 또한, 공정부산물 처분시 대기확산에 의한 방사성핵종의 전이경로와 침출수 유출로 인한 방사성핵종의 전이경로 파악을 수행하고 적절한 코드를 선정하여 예제 평가를 수행함으로써 코드의 유용성을 확인하였다. 그리고 국내 대표 공정부산물인 비산재, 인산석고, 레드머드 특성화 자료를 이용하여 공정부산물 처분시 피폭선량 및 초과 암 리스크를 평가하고 분석하였 다. 개념적 설계 예제에 대한 방사선적 안전성 평가 결과에 의하면 공정부산물 처분시 피폭선량 및 초과 암 리스크는 매우 낮 은 값을 가지며 우려할 만한 방사선적 영향을 보이지는 않는다. 연구결과는 향후 생활방사선 안전관리를 위한 규제기술 개 발에 활용 가능할 뿐만 아니라 생활주변방사선안전관리법 이행기술 기반 구축에 기여할 수 있을 것이다.