The correlation between accident management plan and radiation emergency plan of Shin-Kori Units 3 and 4 was compared and analyzed from the point of view of the adequacy of facilities, equipments, organization and manpower which are necessary for the related emergency response. It was found the equipment of accident management plan and emergency response facility of radiation emergency plan had different technical contents and scope of application, so there was no risk of mutual conflict and overlapping functions. However, since the accident impact assessment code in accident management plan and computer program of radiation emergency plan were different, it was necessary to ensure the agreement or linkage of the evaluation between them. When a radiation emergency is issued in accident management plan, the composition and mission of the accident response organization were mostly consistent with the contents of the radiation emergency plan, but some corrections and improvement items were identified. Accident management plan specified that the disaster response safety center belonged to the emergency operations facility (EOF), but the radiation emergency plan did not mention it at all. The main tasks of disaster response safety center were the movement, arrangement and connection of mobile emergency response facilities, on-site construction of other emergency response facilities, and on-site road restoration. According to the accident management plan, the movement, arrangement, and connection of mobile facilities (i.e., mobile generators, mobile pumps, multi-purpose communication relay facilities), which were considered very important for the prevention and mitigation of serious accidents, were under the supervision of the disaster response safety center. It was stipulated that the operation was carried out with the cooperation of a regular emergency organization, and that the start, operation and stop of mobile equipments were to be performed under the supervision of the emergency operation team supported by the regular emergency organization. Since this organization structure and assignment of duties could not be confirmed in radiation emergency plan, it was necessary to revise and improve the radiation emergency plan for the successful operation of mobile equipments and to link them with the accident management plan.

Since radon was detected in mattresses of famous bed furniture brands in 2018, the nuclear safety and security commission (NSSC) announced the radiation safety management act in April 2021 to protect the public health and environment. This act stipulates the safety management of radiation that can be encountered in the natural environment such as the notification of radioactivity concentration of source materials, process by-products, the installation and operation of radioactive monitors. In this study, a model was established to predict radioactive exposure dose from radioactive materials such as radon and uranium detected in consumer products such as bed mattresses, pillows, shower, bracelets and masks in order to identify major radioactive substances that largely affect the exposure dose. A period of seven years from 2014 to 2020 was investigated for the source materials and exposure doses of consumer products containing naturally occurring radioactive materials (NORMs). We analyzed these using machine learning models such as classification and regression tree (CART), Random Forest and TreeNet. Index development and verification were performed to evaluate the predictive performance of the models. Overall, predictive performance was highest when Random Forest or TreeNet was used for each consumer product. Thoron had a great influence on the internal exposure dose of bedding, clothing and mats. Uranium had a great influence on the internal exposure dose of other consumer products except whetstones. When the number of data is very small or the missing value rate is high, it is difficult to expect accurate predictive performance even with machine learning techniques. If we significantly reduce the missing value rate of data or use the limit of detection value instead of missing values, we can build a model with more accurate predictive performance.

현행 규제요건에 따르면 국내에서 발생된 모든 폐밀봉선원은 자체처분 대상, 극저준위 또는 중·저준위 방사성폐기물에 해 당하며, 기본적으로 방사능 농도를 기준으로 한 처분방식 제한규정을 준수해야 한다. 본 연구에서는 이러한 분류체계 이외 에 IAEA 및 국외 폐밀봉선원 사용국의 방사성폐기물 분류체계, 폐밀봉선원 고유 특성 등에 대한 검토 및 분석결과를 토대 로 반감기 및 A/D 값(각 선원의 방사능(A)을 작업자 및 일반 대중에 대한 잠재적 위험도를 의미하는 방사성핵종 고유의‘D 값’을 활용하여 정규화한 수치로 선원의 상대적 위험을 평가하는 기초적인 기준으로 사용)에 대한 기준을 추가적으로 적용 하여 국내 폐밀봉선원 분류체계에 대한 방안을 제시한 후, 각 범주에 대한 처분방식을 도출하였다. 다양한 처분시점을 상정 한 국내 폐밀봉선원 특성 분석 및 처분방안별 대상 수량·체적 평가결과를 통해 본 연구에서 도출된 처분방안을 처분 예상 시기와 무관하게 2015년 3월말 기준으로 임시저장 중인 모든 폐밀봉선원에 대해 적용할 수 있음을 확인하였다. 단, 방사능 량을 확인할 수 없거나 비방사능 또는 A/D 값을 산출할 수 없는 선원에 대해서는 본 연구결과를 적용할 수 없으므로 처분방 안 이행을 위해서는 사전에 비방사능, 체적 등의 선원 고유 특성이 반드시 확인되어야 한다.

본 연구에서는 중·저준위방사성폐기물 처분시설(이하 처분시설)에서 발생하는 기체의 이동현상을 예측하기 위한 2차원 수 치 모델링을 수행하였다. 또한, 기체 이동 모델링에서 주요 입력변수로 적용되는 사일로 콘크리트의 기체침투압(gas entry pressure)와 기체 투과도(gas permeability)를 실측하여, 모델링 입력변수로 적용하였다. 사일로 콘크리트의 기체침투압(gas entry pressure)와 기체 투과도(gas permeability)는 각각 0.97±0.15 bar 및 2.44×10-17 m2로 측정되었다. 기체 이동 모델링 결과, 사일로 내부에서 발생하는 수소 기체는 기상으로 이동하지 않고 지하수에 용해되어 지하수와 함께 생태계로 이동하는 것을 알 수 있다. 또한, 폐쇄 후 약 1,000 년 후 부터 사일로 상부부터 수소기체 밀도가 증가하기 시작하는 것으로 예측되었 다. 따라서, 사일로 내부에서 발생된 기체는 기상으로 사일로 내부에 축적되지 않으며, 이로 인해 사일로 콘크리트의 내구성 에 영향을 미치지 않을 것으로 판단된다.