When decommissioning nuclear power plant (NPP), the first task performed is cost estimation. This is an important task in terms of securing adequate decommissioning funds and managing the schedule. Therefore, many countries and institutions are conducting continuous research and also developing and using many programs for cost estimation. However, the cost estimated for decommissioning an NPP typically differs from the actual cost incurred in its decommissioning. This is caused by insufficient experience in decommissioning NPPs or lack of decommissioning cost data. This uncertainty in cost estimation can be in general compensated for by applying a contingency. However, reflecting an appropriate standard for the contingency is also difficult. Therefore, in this study, data analysis was conducted based on the contingency guideline suggested by each institution and the actual cost of decommissioning the NPP. Subsequently, TLG Service, Inc.’s process, which recently suggested specific decommissioning costs, was matched with ISDC (International Structure for Decommissioning Costing)’s work breakdown structure (WBS). Based on the matching result, the guideline for applying the contingency for ISDC’s WBS Level 1 were presented. This study will be helpful in cost estimation by applying appropriate contingency guidelines in countries or institutions that have no experience in decommissioning NPPs.

The Korean administration assumed that the amount of low and medium level waste generated during the decommissioning of nuclear facilities in Korea was 14,500 drums (based on 200 L) and designed the LILW repository accordingly. Accordingly, it is necessary to separate the nuclear power plant decommissioning waste into clearance waste by mobilizing means such as decontamination and cutting as much as possible, and to deregulate it together with non-radioactive waste. As a result, clearance waste and non-radioactive waste are dominated by concrete and metal, and it is necessary to evaluate how to recycle them. Many existing studies have conducted research on each recycling method, and accordingly, it can be judged that the technological maturity is sufficient. Accordingly, we would like to propose a method for comprehensive management and evaluation of concrete. By applying the decision matrix proposed in IAEA TRS No. 401, it will be possible to compare the 5 factors (cost, technical feasibility, risk, availability of disposal, and full cycle impact). However, in the case of concrete, if the existing construction waste recycling methodologies are fully used, the technical feasibility can be considered equal. Therefore, it was judged that it would be good to introduce the aspect of public acceptance as an evaluation item instead of technical feasibility. The amount of waste that can be generated when decommission a nuclear power plant is only insignificant compared to the total amount of waste concrete that is generated during the year. Accordingly, one option is to fully integrate the waste concrete recycling system and utilize it for road construction. Next, it is possible to suggest the option of recycling in the construction of shields in the nuclear industry, as suggested in previous studies, and the method of using it as a backfill material such as for a decommissioned NPP site or other sites. As an example, and a draft stage, this study was evaluated based on existing studies after all options were equally weighted. When the profit and loss was evaluated in a way that a maximum of 5 points were given to each option, the case of using it as a backfill in various applications was evaluated as the best option. Unlimited recycling, such as road construction, was evaluated to be highly damaging in terms of public acceptance.

3D modeling is a technology for representing real objects in a virtual 3D space or modeling and reproducing the physical environment. 2D drawings for viewing the existing building structure have limitations that make it difficult to understand the structure. By implementing this 3D modeling, specific visualization became possible. 3D technology is being applied in a wide range of preevaluation work required for nuclear decommissioning. In Slovakia, 3D modeling was applied to determine the optimal cutting strategy for the primary circuit before dismantling the VVER type Bohunice V1. In Japan, the Decommissioning Engineering Support System (DEXUS) program has been developed that incorporates VRDose, a decommissioning engineering support system based on 3D CAD models. Through this, the cutting length of the work object and the quantity of containers for packaging waste are calculated, exposure dose calculations in various dismantling scenarios, and cost estimation are performed. Korea also used 3D technology to evaluate the decommissioning waste volume for Kori Unit 1 and to evaluate the optimal scenario of the decommissioning process procedure for the research reactor Unit 1. 3D technology is currently being used in various pre-decommissioning evaluations for VVER, PWR, and research reactors. Overseas, a program that matches various decommissioning pre-evaluation tasks with cost estimation has also been developed. However, most 3D technologies are mainly used as a support system for dose evaluation and amount of decommissioning waste calculation. In this study, 3D modeling was performed on the PHWR structure, and physical and radiological information about the structure was provided. The information on the structure can present the unit cost for the work object by confirming the standard of the applied unit cost factor (UCF). The UCF presents the unit cost for repeated decommissioning operations. The decommissioning cost of the work object can be obtained by multiplying the UCF by the number of repetitions of the work. If the results of this study are combined with the process evaluation and waste quantity estimation performed in previous studies, it is judged that it will be helpful in developing an integrated NPP decommissioning program that requires preliminary evaluation of various tasks. In addition, it is judged that a clear cost estimation of the object to be evaluated will be possible by matching the 3D work object with the UCF.

The saturation rates of the spent fuel (SF) wet storage at the Kori Nuclear Power Plant (NPP), Hanbit, and Hanul are 83.3%, 74.2%, and 80.8% as of the fourth quarter of 2021. The storages of Kori NPP and Hanbit NPP are expected to be saturated in 2031, and Hanul is expected to be saturated in 2032. Therefore, the construction of an interim storage facility to store the SF temporarily stored in the NPP was planned, and preparations for the safe transport of the SF are required. In this paper, radiological preliminary assessment using NRC-RADTRAN in the process of sea transport of SF from the wet storage or ISFSI of the Hanbit NPP to the optional interim storage facility was performed. Since domestic SF transport vessels are not currently in operation, the specifications of the UK Pacific Grebe vessel which can carry up to 20 casks were used. The transport cask used the specifications of KORAD-21, a transport container developed in Korea. Because it can carry more SF assemblies than the existing KN-18. In addition, a land transport safety test was conducted in 2020 and a sea transport test is planned. The sea transport route was entered by referring to the transport route of domestic low and intermediate level waste. The accidents rate was calculated using statistics on maritime accidents from 2017 to 2021. The probability accidents along the transportation route were evaluated as 3.152E -10. When transporting to an interim storage facility, the SF expected to be the main transport target was selected as WH 17X17, combustion 45,000 MWD/MTU, and concentration of 4.5%. The source term was calculated and entered according to this data and the release fraction was entered with reference to the DOE report. In the case of normal transport without accident, the individual dose of the crew member and public residents were estimated to be 0.0525% and 0.000492% of the annual limit of 1 mSv/yr for the general public. Under the accident conditions, the annual individual doses of residents were 0.0011%, 0.0023%, 0.0034%, and 0.0046% of the annual limit of 1 mSv/yr when carrying 5, 10, 15, and 20 casks. Currently, the site of the interim storage facility has not been precisely determined, but a preliminary radiation assessment through sea transport resulted in a significantly lower than the limit. Combined scenario sea transport followed by land transport will be carried out in the next stage of study.

사이클로트론 가동 시 핵반응으로 인해 중성자가 발생되며, 발생된 중성자는 콘크리트벽에 흡수되어 방 사화를 일으키게 된다. 이에 본 연구에서는 콘크리트 종류에 따른 방사화 분석과 방사화 핵종이 미치는 영향에 대해 알아보고자 하였다. 실험은 몬테카를로 시뮬레이션 및 RESRAD 모델을 사용하였다. 실험 결과 콘크리트의 Fe 함유량이 높을수록 차폐율이 증가하였으며, Fe은 56Fe(n, 2np)54Mn 반응으로 인하여 종사자 에게 미치는 영향 또한 같이 증가하였다. 하지만, 방사화로 생성된 핵종의 방사능은 매우 낮게 나타나 종사 자들에게 미치는 영향은 매우 낮은 것으로 나타났다. 방사화된 콘크리트 해체 처분 시 방사능이 자체처분 한도 미만으로 일반폐기물로써 처리되어야 하며, 14C의 영향을 최소화하기 위해 매립이 아닌 도로 보수와 같은 표층에 재활용 되어야 할 것이다.

원전의 안전한 해체 관리를 위해 원전 해체 비용 평가는 매우 중요하다. 가장 많은 원전 해체 경험을 갖고 있는 미국의 경우 1970년대부터 원자력시설의 해체를 위하여 비용평가 연구를 진행하였다. 미국 NRC는 다양한 로형 및 원자력시설에 대한 해체 기술, 안전성 및 비용에 대한 연구를 수행하였다. 전체 해체 비용에서 운영허가종료비용이 가장 큰 비중을 차지하며, 그 다음으로는 사용후핵연료 관리, 부지복원순으로 평가되었다. 해체비용은 전체비용에 있어 운영허가종료가 제일 큰 비중을 차지하며 사용후핵연료관리, 부지복원 순으로 평가되었다. 즉시해체의 경우 지연해체에 비해 사용후핵연료관리 비용이 증가하였으며 지연 해체의 경우 운영허가종료의 비용이 증가하였다. 전반적으로 즉시해체에 비해 지연해체의 경우가 뚜렷하게 이득이 보이지 않고 있다. 국내 원전 해체 비용 평가시 부지 조건에 따른 평가를 고려해야할 필요가 있다고 판단된다. 또한 국내의 경우 IAEA의 권고사항을 적용하여 방사성폐기물 분류체계를 재정비하였다. 이에 따라 해체시 발생하는 방사성폐기물 물량 산정시, 선행 미국 원전해체 자료를 신분류체계에 적합하게 활용하기 위한 방법을 개발해야할 필요가 있다. 특히 자체처분 대상폐기물 평가 방법론 설정은 해체비용의 정확성을 확보하는 중요한 인자로 작용할 것이다. 또한 국내 원전해체 비용 평가를 위하여 시설 특성과 작업 특성에 적용할 수 있는 정보자료 구축이 필요하다.