High level radioactive waste (HLW) final disposal repository is faced thermos-hydro-mechanical - radioactive condition because it is placed over 500 m in depth and waste emits decay heats for decades. Repository will be operated around 100 years and will be closed after all the wastes are disposed. The integrity of engineered barriers including buffer, backfill, concrete plug and canister and natural barrier (natural rock mass) will be stood during operating periods. Monitoring sensors for concrete and rock mass is conducted using piezo based sensors such as accelerometer or acoustic emission (AE) sensors. Typical accelerometer for harsh conditions is commonly expensive and data/power cable can be a potential groundwater inflow and nuclide outflow path. The fiber optic accelerometer whose data and power cable are united and has limited volume. Therefore, it can be a potential alternative sensor of piezo based sensors. The temperature limits and accelerated tests for fiber optic sensors are conducted. Most of sensors gives a malfunction around 130°C. The results of these experimental tests give a possibility of communications in compacted bentonite buffer and will be utilized for the design of monitoring systems for the repository.

Deep borehole drilling is essential not only to select the host rock type for deep geological disposal of high-level radioactive waste (HLW), but also to identify the characteristics of the disposal site during the site selection process. In particular, since the disposal depth of HLW is considered to be over 300 m, deep borehole drilling must be performed. In deep borehole drilling, drilling design, excavation, and operation may vary depending on the rock type, drilling depth, and drilling purpose etc. This study introduced cases in which Korea was divided into four geotectonic structures and four representative rock types and conducted with a goal of 750 m drilling depth. Prior to this, a review of deep drilling cases conducted at domestic and abroad was presented. If sufficient time and cost are available, several drilling holes can be excavated for various purposes, but if not, one or two drilling holes should be used to achieve the objectives of various fields related to HLW disposal. The presence of bedding, strata or fault zones depending on the type of rock, etc. may affect drilling deviation or circulating water management. In addition, unlike drilling in general geotechnical investigation drilling, the use of polymers or grouting agents is limited to determine hydraulic and geochemical characteristics. This report introduces the experience considered during the design and drilling process of deep drilling in granite, gneiss, sedimentary rock, volcanic rock, etc., and is expected to be used as basic data when carrying out future HLW projects.

With the importance of permanent disposal of high-level radioactive waste (HLW) generated in Korea, the deep geological disposal system based on the KBS-3 type is being developed. Since the deep geological repository must provide the long-term isolation of HLW from the surface environment and normal habitats for humans, plants, and animals, it is essential to assess the longterm performance of the disposal facility considering thermal-hydraulic-mechanical-chemical (TH- M-C) evolution. Decay heat dissipated from HLW contained in the canister causes an increase in temperature in the adjacent area. The requirement for the maximum temperature is established in consideration of the possibility of bentonite degradation. Therefore, when designing the repository, the temperature in the region of interest should be identified in detail through the thermal evolution assessment to ensure that the design requirement is satisfied. In the thermal evolution analysis, it is needed to evaluate the temperature distribution over the entire area of the disposal panel to consider the heat generated from both a single canister and adjacent canisters. Computational fluid dynamics (CFD) codes are widely used for detailed temperature analysis but are limited to simulating a wide range. Accordingly, in this study, we developed an analytical solution-based program for efficiently calculating the temperature distribution throughout the deposition panel, which is based on threedimensional heat conduction equations. The code developed can assess the temperature distribution of engineered and natural barrier systems. Principal parameters to be inputted are as follows: (a) geometry of the panel (e.g. width, length, height, spacing between canisters), (b) geometry of the canister (e.g. diameter, height), (c) thermal properties of bentonite and host-rock, (d) initial conditions (e.g. residual heat, temperature), and (e) time information (e.g. canister emplacement rate, time-interval, period). Through the calculation for the conceptual problem of a deposition panel capable of accommodating 900 (i.e. 30×30) canisters, it was confirmed that the program can adequately predict when and where the maximum temperature will occur. It is expected that the overall temperature distribution within the panel can be obtained by the evaluation of the entire region using this program reflecting the detailed design of the repository to be developed in the future. In addition, the thermal evolution analysis considering the influence of other canisters can be performed by applying the results as boundary conditions in the CFD analysis.

IAEA safety standards document and international programs (such as BIOMASS) related to the assessment of the biosphere around High Level Radioactive Waste (including Spent Nuclear Fuel) repositories require the assessment of the biosphere to use the assumption that the current natural environment and human society will be maintained, and at the same time, the evolution of the distant future changes also need to be taken into account. In Korea, which has not designated candidate disposal sites, it is necessary to investigate and predict the current state and future changes of the natural environment throughout Korea and apply it practically to Biosphere assessment (for BDCF derivation) for candidate disposal sites suitability assessment and Safety Case (for performance assessment) preparation for design, construction, operation, and post-closure management. To this end, the natural environment in the fields of Topography, Geology, Soil, Ecology, Weather and Climate, Animals and Plants, Hydrology, Ocean, Land-use, etc. and human society in the fields of Population Distribution, Spatial-Planning, Urban Form, Industrial-Structure, Lifestyle etc. are being investigated in the context of current status, past change records, and future change potential in the Korean Peninsula. This paper summarizes those investigations to date. This study referred Biomass-6 [IAEA] and National Atlas I (2019)/II (2020)/III (2021) [National Geographic Information Institute of the Korea Ministry of Land, Infrastructure and Transport].

As of 2023, there has been significant progress worldwide in the management of nuclear fuel’s spent radioactive waste (HLW). Several countries have made important strides in advancing their plans for the construction of deep geologic repositories (DGRs) to safely dispose of their nuclear waste. Finland led the way, with its nuclear waste management organization, Posiva Oy, submitting an application for an operating license for a DGR for spent fuel generated by the nuclear power plants of its owners. The facility, ONKALO, will be located on the island of Olkiluoto and is expected to begin final disposal in the mid-2020s. Sweden also approved SKB’s application to build a DGR in Forsmark, and an encapsulation plant next to the Clab interim storage facility. In Switzerland, Nagra selected Nordic Lagern as the site for the Swiss DGR, and is preparing the general license applications for the required facilities. Meanwhile, Canada’s Nuclear Waste Management Organization (NWMO) narrowed down the possible locations for its DGR to two, and expects to name its preferred site by fall 2024. The UK established four Community Partnerships to participate in the siting process for a DGR, with Nuclear Waste Services (NWS) responsible for identifying a site. Andra, the French organization responsible for managing all French radioactive waste, is expected to submit an application by the end of the year for a DGR in France that will contain HLW resulting from reprocessing of spent fuel assemblies from French nuclear power plants, as well as intermediate-level waste. Overall, the progress made by these countries represents a tangible and sustainable step forward in the management of spent fuel and HLW, and brings us closer to the safe and effective long-term disposal of nuclear waste.

Large earthquakes with (MW > ~ 6) result in ground shaking, surface ruptures, and permanent deformation with displacement. The earthquakes would damage important facilities and infrastructure such as large industrial establishments, nuclear power plants, and waste disposal sites. In particular, earthquake ruptures associated with large earthquakes can affect geological and engineered barriers such as deep geological repositories that are used for storing hazardous radioactive wastes. Earthquake-driven faults and surface ruptures exhibit various fault zone structural characteristics such as direction of earthquake propagation and rupture and asymmetric displacement patterns. Therefore, estimating the respect distances and hazardous areas has been challenging. We propose that considering multiple parameters, such as fault types, distribution, scale, activity, linkage patterns, damage zones, and respect distances, enable accurate identification of the sites for deep geological repositories and important facilities. This information would enable earthquake hazard assessment and lower earthquakeresulted hazards in potential earthquake-prone areas.

고준위 방사성폐기물 처분에 대한 종합 성능 평가를 위해 처분장 성능 및 안전성에 미치는 영향들을 단위 현상, 사건, 공정 (FEP)으로 분류하고 이들을 발생 가능성, 결과 영향, 규제, 특정 부지의 적합성 등을 고려하여 중요도를 평가한 후 유사한 FEP들을 그룹화하여 이들 FEP 그룹들 간의 상호 반응을 이해하고 이로부터 처분장으로부터 최종 생태계에 이르는 방사성 핵종들이 이동을 기술하는 시나리오를 도출하는 연구가 필요하다. 한국원자력연구원에서는 외국의 사례를 심층 분석하고 국내 전문가 의견 등을 종합하여 국내 처분 환경에 적합한 FEP들을 380 여개 포함하는 KAERI FEP List를 개발하였다. RES와 PID방법을 사용하여 처분장 방사선적 종합 안전성 평가에서 고려해야 될 5 가지 시나리오들을 도출하였다. 또한 고준위폐기물 처분안전성평가를 종합 데이터베이스 관리시스템인 KAERI CYPRUS를 개발하고 이들 결과물을 CYPRUS 내에 구축하였다.

고준위 방사성폐기물 처분에 대한 종합 성능 평가를 위해 처분장 성능 및 안전성에 미치는 영향들을 단 위 현상, 사건, 공정 (FEP)으로 분류하고 이들을 발생 가능성, 결과 영향, 규제, 특정 부지의 적합성 등을 고려하여 중요도를 평가한 후 유사한 FEP들을 그룹화하여 이들 FEP 그룹들 간의 상호 반응을 이해하고 이로부터 처분장으로부터 최종 생태계에 이르는 방사성 핵종들이 이동을 기술하는 시나리오를 도출하는 연구가 필요하다. 한국원자력연구원에서는 외국의 사례를 심층 분석하고 국내 전문가 의견 등을 종합하 여 국내 처분 환경에 적합한 FEP들을 380 여개 포함하는 KAERI FEP List를 개발하였다. RES와 PID방법 을 사용하여 처분장 방사선적 종합 안전성 평가에서 고려해야 될 5 가지 시나리오들을 도출하였다. 또한고준위폐기물 처분안전성평가를 종합 데이터베이스 관리시스템인 KAERI CYPRUS를 개발하고 이들 결 과물을 CYPRUS 내에 구축하였다.