• Economic and Environmental Geology
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• v.56 no.5
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• pp.533-545
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• 2023

In this study, an investigation was conducted on the features, events, and processes (FEP) that could impact the long-term safety of the natural barriers constituting high-level radioactive waste geological repositories. The FEP list was developed utilizing the IFEP list 3.0 provided by the Nuclear Energy Agency (NEA) as foundational data, supplemented by geological investigations and research findings from leading countries in this field. A total of 49 FEPs related to the performance of the natural barrier were identified. For each FEP, detailed definitions, classifications, impacts on long-term safety, significance in domestic conditions, and feasibility of quantification were provided. Moreover, based on the compiled FEP list, three scenarios that could affect the long-term safety of the disposal facility were developed. Geological factors affecting the performance of the natural barrier in each scenario were selected and their relationships were visualized. The constructed FEP list and the visualization of interrelated factors in various scenarios are anticipated to provide essential information for selecting and organizing factors that must be considered in the development of mathematical models for quantitatively evaluating the long-term safety of deep geological repositories. In addition, these findings could be effectively utilized in establishing criteria related to the key performance of natural barriers for the confirmation of repository sites.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.121-130
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• 2018

The KURT (KAERI Underground Research Tunnel) is a research tunnel which is located in KAERI (Korea Atomic Energy Research Institute) site. At KURT, researches on engineering and natural barrier system, which are the most important components for geological disposal system for high level radioactive waste, have been conducted. In this study, we synthesized the site characteristics obtained by various types of site investigation to introduce the geological model for KURT site, and induced the 3-D hydrogeological model for KURT site from the geological model. From the geological investigation at the surface and boreholes, four geological elements such as subsurface weathered zone, upper fractured rock, lower fractured rock and fracture zones were determined for the geological model. In addition, the geometries of these geological elements were also analyzed for the geological model to be three-dimensional. The results from 3-D geological model were used to construct the hydro-geological model for KURT site, which is one of the input data for groundwater flow modeling and safety assessment.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.229-245
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• 1997

There are Common aspects between the underground oil storage cavern and the radioactive waste disposal facility. Both facilities use appropriately the intrinsic natural berrier characteristics of the rock mass and additionally the engineered barrier system for the long term safety. The geological structures and their hydrogeological characteristics in a faactured rock mass act a major role in the safety and performance of the underground oil storage facility through the design, construction and the operation stages. Because the fracture system distributed in a fractured rock block is complicated owing to their own geometrical and hydrogeological attributes, the hydrogeological perforrmrnce of the facility would depend mainly upon the understandings of their characteristics. This study reviews the uncertainties and key issues which have to be considered to analyse the groundwater flow system in a fractured rock mass and proposes the techniques applicable to characterize the hydrogeological parameter.

• Economic and Environmental Geology
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• v.56 no.2
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• pp.167-183
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• 2023

Gases originated from the final SNF (spent nuclear fuel) disposal site are very mobile in the barrier and they may also affect the migration of radioactive nuclides generated from the SNF. Mechanisms of gas-nuclide migration in the multi-barrier and their influences on the safety of the disposal site should be understood before the construction of the final SNF disposal site. However, researches related to gas-nuclide coupled movement in the multi-barrier medium have been very little both at home and abroad. In this study, properties of gas generation and migration in the SNF disposal environment were reviewed through previous researches and their main mechanisms were summarized on the hydrogeological evolution stage of the SNF disposal site. Gas generation in the SNF disposal site was categorized into five origins such as the continuous nuclear fission of the SNS, the Cu-canister corrosion, the oxidation-reduction reaction, the microbial activity, and the inflow from the natural barriers. Migration scenarios of gas in porous medium of the multi-barrier in the SNF repository site were investigated through reviews for previous studies and several gas migration types including ① the free gas phase flow including visco-capillary two-phase flow, ② the advection and diffusion of dissolved gas in pore water, ③ dilatant two-phase flow, and ④ tensile fracture flow, were presented. Reviewed results in this study can support information to design the further research for the gas-nuclide migration in the repository site and to evaluate the safety of the Korean SNF disposal site in view points of gas migration in the multi-barrier.

• Journal of the Korean earth science society
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• v.44 no.6
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• pp.629-642
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• 2023

Currently, low and intermediate level radioactive waste is being disposed of at the Gyeongju disposal site for permanent isolation. Since 2006, the Korea Radioactive Waste Agency has been conducting site characteristics surveys continuously verifying changes in the site based on the site monitoring and investigation plan. The hydrogeochemical environment of the disposal site is considered for the evaluation of natural barriers. However, the seawater must be considered because of the regional characteristics of Gyeongju, which is near the East Sea. Therefore, this study, collected 30 samples for deriving the groundwater quality data from seven wells and compared with two seawater samples collected from October 2017 to June 2022. Additionally, the study explores the groundwater monitoring method using statistical tools such as clustering and background concentration analysis. The groundwater samples in the study area were classified into two to four clusters depending on their chemical constituents-especially, EC, HCO₃, Na, and Cl-using statistical analysis, molar ratio, and K-means clustering.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.3
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• pp.199-208
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• 2012

To develop site characterization technologies for a radioactive waste disposal research in KAERI, the geological and hydrogeological investigations have been carried out since 1997. In 2006, the KURT (KAERI Underground Research Tunnel) was constructed to study a solute migration, a microbiology and an engineered barrier system as well as deeply to understand geological environments in in-situ condition. This study is performed as one of the site characterization works around KURT. Several investigations such as a lineament analysis, a borehole/tunnel survey, a geophyscial survey and logging in borehole, were used to construct the geological model. As a result, the geological model is constructed, which includes the lithological model and geo-structural model in this study. Moreover, from the results of the in-situ hydraulic tests, the hydrogeological properties of elements in geological model were evaluated.

• The Journal of Engineering Geology
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• v.9 no.1
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• pp.45-57
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• 1999

Groundwater flow in rock mass is controlled by the fractures developed in the area. So, the conductive fractures are very important for groundwater flow in crystalline rock. This study aims to find out the characteristics of the fracture distributed in granitic rock in the northern part of the Yusong area (latitude $36^{\circ}24'18"~36^{\circ}25'08",{\;}longitude{\;}127^{\circ}21'00"~127^{\circ}23'23"$). The electric and EM surveys were carried out in the site to delineate the fracture the fracture zones. Since geophysical survey provides non-unique solution, hydraulic data and dilling log data including BHTV scanning were used as complementary data to achieve the objective of this study. Electric survey(DC) arrays used are schlumberger and dipole-dipole arrays. VLF is used for EM survey. The main charcteristics of the fracture developed in the study aera are that fractures associated with basic dyke cut corss the main fracture zone in NNW and play an important role as hydraulic barrier. In trun, groundwater table in the upstream area is lower than that downstream area.

• The Journal of Engineering Geology
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• v.9 no.2
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• pp.89-100
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• 1999

This study was carried out to assess the physicochemical properties of domestic bentonites and zeolites from Tertiary Formation as the candidate material for a engineered barrier of a radioactive waste repository. Natural bentonite and zeolite samples were collected from nine bentonite mines and six zeolite mines in Yeonil-Gampo area. The commercial products of bentonite and zeolite were obtained from local companies. The collected samples were investigated to study the following physicochemical properties: X-ray diffraction patterns, swelling, cation exchange capacity(CEC), specific surface area, montmorillonite content, pH, organic carbon content, thermal property, microstruciure and chemical composition. Based on the physicochemical properties of bentonite and zeolite, the bentonites from U-41 and G-46 mines and the zeolites from Daedo and Y-1 mines are regarded as the most desirable candidate materials.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.251-260
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• 2016

Groundwater flow due to hydraulic gradients across a geologic barrier surrounding a dam reservoir can cause swamps or wetlands to form on the downstream side of the dam, thereby restricting land use. The difference in head between the reservoir level and the downstream groundwater level creates a hydraulic gradient, allowing water to flow through the geologic barrier. We constructed a drainage system at the Daecheong dam to study the effects on groundwater levels and soil moisture contents. The drainage system consisted of a buried screened pipe spanning a depth of 1-1.5 m below a land surface. Groundwater levels were monitored at several monitoring wells before and after the drainage system was installed. Most well sites recorded a decline in groundwater level on the order of 1 m. The high-elevated site (monitoring well W1) close to the reservoir showed a significant decline in groundwater level of more than 2 m, likely due to rapid discharge by the drainage system. Soil moisture contents were also analyzed and found to have decreased after the installation of the drainage system, even considering standard deviations in the soil moisture contents. We conclude that the drainage system effectively lowered groundwater levels on the downstream side of the dam. Furthermore, we emphasize that water seepage analyses are critical to embankment dam design and construction, especially in areas where downstream land use is of interest.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.1
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• pp.63-75
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• 2012

This paper gives some basic requirements and preferences of various geological environmental conditions for the final deep geological repository of spent nuclear fuel (SNF). This study also indicates how the requirements and preferences are to be considered prior to the selection of sites for a site investigation as well as the final disposal in Korea. The results of the study are based on the knowledge and experience from the IAEA and NEA/OECD as well as the advanced countries in SNF disposal project. This study discusses and suggests preliminary guideline of the disposal requirements including geological, mechanical, thermal, hydrogeological, chemical and transport properties of host rock with long term geological stabilities which influence the functions of a multi-barrier disposal system. To apply and determine whether requirements and preferences for a given parameter are satisfied at different stages during a site selection and suitability assessment of a final disposal site, the quantitative criteria in each area should be formulated with credibility through relevant research and development efforts for the deep geological environment during the site screening and selection processes as well as specific studies such as productions of safety cases and validation studies using a generic underground research laboratory (URL) in Korea.