PURPOSES : In this study, the amount of core stone breaking in the size of boulders by excavator braker work was analyzed quantitatively through on-site test construction. In addition, the factors affecting workload were studied. METHODS : In the field test, 30 core stones of boulder sizes (1–4 m3) that appeared during earthworks, such as road construction and site construction, were collected from three locations, and the rock breaking work was carried out simultaneously using three excavator breakers(1.0-m3 volume). During the core stone breaking, progress was analyzed through video recordings. RESULTS : After the completion of rock breaking, the amount of breaking work was analyzed by direct loading and weighing using a 15- ton dump truck. As a result of the test construction, there was a significant difference in the amount of work completed per hour. CONCLUSIONS : It was found that the results were greatly affected by not only the performance of the excavator braker equipment, but also the skill of the driver and the size of the core stones.

Low to intermediate radioactive waste disposal concrete structures are subjected to coupled hydromechanical conditions and the identification of structural damage is crucial to ensure safe long-term disposal. Different damage models for concrete and the surrounding rock can affect the damage characteristics of radioactive waste disposal structures. In this study, the effects of different rock damage models are applied to the hydro-mechanical-damage coupled structural analysis of the Wolseong Low and Intermediate Level Radioactive Waste Disposal Center silo. A two-dimensional model of the disposal silo was modeled using the finite element analysis software COMSOL and the Mazars’ damage model was applied to the silo concrete. The Mazars’ model parameters were obtained from uniaxial compression and tensile tests on cylindrical concrete specimens after 28 days of water curing and further 32 days of wet curing at 75°C). The COMSOL embedded Richards equation module was used to simulate hydraulic analysis. Structural loading due to waste disposal was applied at the bottom of the silo structure and the damage evolution characteristics were investigated. The non-linear mechanical rock behavior obtained from laboratory tests (Hoek-Brown criterion, resonant column test, Mazar’s damage model) and field tests (Goodman Jack) were input to assess the effects of different rock damage models. The results highlight the importance of structural damage consideration when assessing the long-term stability and safety of underground radioactive waste disposal structures under coupled hydro-mechanical conditions.

To decrease area of the repository for high-level radioactive waste, enhancing the disposal efficiency is needed for public acceptance. Previous studies regarding the performance assessment of KRS and KRS+ repository did not consider area-based variations of the geothermal gradient and rock thermal properties in Korea. This research estimated deposition hole spacing based on performance assessment of a repository using the distribution of geothermal gradient and rock thermal properties in Korea to increase disposal efficiency. Distributions of geothermal gradient, rock thermal properties were investigated based on 2019 Korea geothermal atlas published by Korea Institute of Geoscience and Mineral Resources (KIGAM). Effect of thermal performance parameters was analyzed using coupled thermal-hydraulic numerical simulations, and effect of rock thermal conductivity and deposition hole spacing on the maximum temperature of buffer was relatively large. In addition, distribution maps of thermal performance of a repository and deposition hole spacing were plotted using thermal performance parameters-maximum temperature of buffer regression equations and GIS data given by KIGAM. In the regions showing the highest maximum temperature of buffer in Korea, required deposition hole spacings were 10.5 m, 10.0 m, 10.1 m, respectively for KJ-II, MX-80, and FEBEX bentonite cases, and thereby additional disposal area of 40%, 33.3%, and 34.7% were required compared to that of the KRS+ repository. On the other hand, high disposal efficiency can be obtained in the regions showing the low maximum temperature of bentonite buffer. The methodology provided in this research can be used as one of the references for the selection of domestic candidate repository sites. Additional mechanical performance analysis should be conducted using distributions of mechanical properties of rock mass in Korea.

The design of the high-level radioactive waste (HLW) repository is made for isolating the HLW from the groundwater system by using artificial and natural barriers. Granite is usually considered to be a great natural barrier for the HLW repository in various countries including Sweden, Canada, and Korea due to its low hydraulic permeability. However, many fractures that can act as conduits for groundwater and radionuclides exist in granite. Furthermore, the decay heat generated by the HLW can induce groundwater acceleration through the fracture. Since the direction, magnitude, and lasting time of the heat-induced groundwater flow can be differed depending on the fracture geometry, the effect of fracture geometry on the groundwater flow around the repository should be carefully analyzed. In this study, groundwater models were conducted with various fracture geometries to quantify the effect of various properties of fractures (or fracture networks) on the heat-induced groundwater flow. In all models, the pressure around the repository only lasted for a short period after it peaked at 0.1 years. In contrast, the temperature lasted for 10,000 years after the disposal inducing the convective groundwater flow. Single fracture models with different orientations were conducted to evaluate the variations in groundwater velocities around the repository depending on the fracture slope. According to the results, the groundwater velocity on the fracture was the fastest when the regional groundwater flow direction and the fracture direction coincided. In double fracture models, various inclined fractures were added to the horizontal fracture. Due to the intersecting, the groundwater flow velocity showed a discontinuous change at the intersecting point. Lastly, the discrete fracture network models were conducted with different fracture densities, length distributions, and orientations. According to the modeling results, the groundwater flow was significantly accelerated when the fracture network density increased, or the average fracture length increased. However, the effect of the fracture orientation was not significant compared to the other two network properties.

With the increase of temporarily-stored spent radioactive fuels, there is an increasing necessity for the safe disposal of high-level radioactive waste (HLW). Among various methods for the disposal of HLW, a deep geological disposal system is adapted as a HLW disposal strategy in many countries. Before the construction of a repository in deep geological condition, a performance assessment, which means the use of numerical models to simulate the long-term behavior of a multi-barrier system in HLW repository, has been widely performed to ensure the isolation of radionuclides from human and related environments for more than a million years. Meanwhile, Korea Atomic Energy Research Institute (KAERI) is developing a process-based total system performance assessment framework for a geological disposal system (APro). To improve the reliability of APro, KAERI is participating in DECOVALEX-2023 Task F, which is the international joint program for the comparison of the models and methods used in deep geological performance assessment. As a final goal of Task F, the reference case for a generic repository in fractured crystalline rock is described. The three-dimensional generic repository is located in a domain of 5 km in length, 2 km in width, and 1 km in depth, and contains an engineering barrier system with 2,500 deposition holes in fractured crystalline rock. In this study, a numerical simulation of the reference case is performed with COMSOL Multiphysics as a part of Task F. The fractured crystalline rock is described with the discrete fracture matrix (DFM) model, which expresses major deterministic fractures explicitly in the domain and minor stochastic fractures implicitly with upscaled quantities. As an output of the numerical simulation, fluid flow at steady-state and radionuclide transport are evaluated for ~106 years. The result shows that fractures dominate the transport of radionuclides due to much higher hydraulic properties than rock matrix. The numerical modeling approaches used in this study are expected to provide a basis for performance assessment of nuclear waste disposal repository located in fractured crystalline rock.

이 연구는 국토지리정보원, 국립해양조사원, 한국국토정보공사 등 관계기관에서 제작된 독도지도에 독도의 부속도서 수가 상이하게 표현되고 있는 문제로부터 시작되었다. 따라서 이 연구는 독도에 지번이 처음으로 부여되었던 시점부터 현재까지 관계기관 및 민간지도제작사에서 제작된 독도지도를 분석함으로써 문제의 원인을 찾아내고, 정책적 제언을 하는 것이 목적이다. 연구결과, 첫째, 독도 주변에 분포하는 바위섬이나 암초들을 부속도서로 통칭하는 것은 무리가 있는 것으로 판단된다. 관계기관에서는 바위섬과 암초를 명확하게 구분하고, 부속도서라는 명칭을 계속해서 쓸 것인지, 또는 선별적으로 쓸 것인지 여부를 논의할 필요가 있다. 둘째, 독도의 산정부에서 떨어진 암석 덩어리까지 부속섬으로 집계되는 경우도 있는데, 이는 현지조사가 제대로 이루어지지 않은 문제라 사료된다. 따라서 관계기관에서는 독도 주변의 바위섬과 암초의 분포를 명확하게 파악한 후 지도화 작업을 해야 할 것이다. 끝으로, 바위섬과 암초에 부여된 지번을 계속 유지할 것인지 여부를 심도있게 논의할 필요가 있다. 규모가 작은 바위섬이나 암초의 경우는 풍화작용이나 파식작용에 의해 언제든지 사라질 수도 있기 때문에 이들 부속섬에 지번을 부여하는 문제는 신중할 필요가 있다.

본 연구의 목적은 암석 판별 탐구에서 중학교 영재학생들의 과학적 관찰과 추론의 특징을 탐색하기 위함이었다. 이를 위하여 영재교육원에 다니는 19명의 중학교 1학년 학생들에게 과학 교과서에서 중요하게 다루는 화성암, 변성암, 퇴적암이 포함된 5가지 암석 샘플을 나누어 주고 각 암석의 형성과정, 종류, 이름 등을 유추해 보도록 하였다. 연구 결과, 학생들이 주로 주목하는 암석의 특징은 색, 조직, 구조로 나타났다. 전형적인 암석의 경우 기억에 의존하여 즉각적으로 암석 판별에 성공하나 관찰에 근거한 유의미한 추론이 이루어지지 못하는 반면, 판별에 어려움을 겪는 암석의 경우 관찰에 근거한 유의미한 추론 과정이 담화를 통해 드러나기도 하였다. 또한 유의미한 관찰 결과로부터 과학적 추론 을 타당하게 구성하였으나 암석 판별에 실패한 경우도 나타났다. 본 연구 결과는 중학생들의 암석 판별 탐구 활동에서 학생들의 현 수준을 파악하고, 학교 현장에서 이루어지는 암석 판별 탐구가 학생들에게 과학적 관찰과 추론의 경험을 제공할 수 있도록 방안을 모색하고, 시사점을 제공하고자 한다.

피암터널은 낙석방지시설 중 하나로 비교적 큰 낙석이 발생할 수 있는 급경사지 도로위에 건설된다. 일반적으로 피암터널은 약 200kJ에서 3,000kJ 까지의 낙석에너지에 저항할 수 있도록 설계된다. 기존 연구에서 이러한 피암터널의 효율성을 증대하기 위하여 콘크리트 충전강관(CFT, Concrete-Filled Tube)를 주구조체로 사용하는 신형식 피암터널을 제시하였다. CFT를 주구조체로 활용함으로서 급속시공이 가능하며 높은 하중저항 능력과 연성 또한 확보할 수 있는 장점이 있다. 하지만, 기존 연구에서는 선현 탄성 해석을 통하여 거동을 분석하여 한계를 가지고 있어 보다 실제적인 낙성하중을 고려한 3차원 유한요소해석을 통하여 제안된 피암터널의 거동을 분석할 필요가 있다. 본 연구에서는 먼저 제안된 피암터널 주구조체에 대한 실제 낙석하중을 포함한 3차원 유한요소해석을 개발하였다. 이후 최대 낙석에너지에 대한 제안된 피암터널 주구조체의 낙석 저항능력에 대하여 연구를 수행하였다.