• Tunnel and Underground Space
• /
• v.34 no.4
• /
• pp.312-329
• /
• 2024

In various underground research projects such as energy storage and development and radioactive waste disposal targeting deep underground, the characteristics of permeable rock fractures that serve as major pathway of groundwater flow in deep rock aquifer are considered as an important evaluation factor in the design, construction, and operation of research facilities. In Korea, there is little research and database on the location and hydraulic characteristics of permeable rock fractures and the pattern of groundwater flow patterns that may occur between fractures in deep rock boreholes. In this paper, the hydraulic characteristics of permeable rock fractures in deep rock aquifer were evaluated through the analysis of geothermal gradient and pumping test data. First, the deep geothermal distribution was identified through temperature logging, and the geothermal gradient was obtained through linear regression analysis using temperature data by depth. In addition, the hydraulic characteristics of the fractured rock were analyzed using outflow temperature obtained from pumping tests. Ultimately, the potential location and hydraulic characteristics of permeable rock fractures, as well as groundwater flow within the boreholes, were evaluated by integrating and analyzing the geophysical logging and hydraulic testing data. The process and results of the evaluation of deep permeable rock fractures proposed in this study are expected to serve as foundational data for the successful implementation of underground research projects targeting deep rock aquifers.

• Tunnel and Underground Space
• /
• v.14 no.3
• /
• pp.175-187
• /
• 2004

고준위방사성폐기물 처분의 경우 심부 암반에 만들어진 처분장에 영구 처분하는 것이 최선의 방안으로 여겨지고 있다. 하지만 지하 심부의 암반에 대한 물리적, 화학적, 역학적, 열적, 수리적 물성과 이들과 핵종 이동의 관계, 처분환경에서의 공학적 방벽 및 암반의 거동이 처분장 안정성 및 안전성에 미치는 영향 등을 파악해야하는 어려움이 따른다. 특히 고준위폐기물 처분의 경우 장기간의 안전성을 고려해야하기 때문에 자연방벽과 공학적 방벽의 시간에 따른 거동변화도 고려하여야 할 필요가 있다. (중략)

• Tunnel and Underground Space
• /
• v.34 no.5
• /
• pp.503-526
• /
• 2024

In the research project for the disposal of high-level radioactive waste, where the deep rock environment is considered as the main target for the disposal facilities, the hydrogeological characteristics of rock aquifers are utilized as the most important evaluation factor for the suitability of the disposal site, design/construction of facilities and stability analysis during operation. Such hydrogeological data are obtained by conducting in-situ hydraulic tests using deep boreholes located at the target sites. In this process, the reliability and accuracy of the investigation results are closely linked to various factors including the selection of the optimal testing methods, the performance of testing equipment, the standardization of testing procedures, and data interpretation methods. In this paper, to improve the reliability of the evaluation of hydrogeological characteristics in deep rock aquifers, we conducted a comparative analysis of the hydraulic conductivity characteristics derived from the injection and recovery phases of the most representative hydraulic test, the constant pressure injection test. A high-performance hydraulic testing equipment and standardized testing procedures were applied to deep boreholes in the fractured rock aquifers located in granite/volcanic rock areas in Korea, to obtain the downhole pressure-flow rate, and the hydraulic conductivity was derived by using various transient flow analysis solutions. The results of the study showed a high consistency between the hydraulic conductivity values obtained during the injection and recovery phases within the same test section, even under different permeability conditions (low-permeability/high-permeability). This research case, which precisely conducted a comparative analysis of two different phases (injection/recovery) within a single specific hydraulic testing process using actual field data from deep rock aquifers in Korea, is expected to help overcome the inherent limitations of in-situ field tests, where the validation and verification of measurement results are challenging, and ultimately contribute to enhancing the reliability of deriving in-situ hydrogeological characteristics information.

• Tunnel and Underground Space
• /
• v.32 no.6
• /
• pp.435-450
• /
• 2022

In step-by-step site selection for geological disposal of high-level radioactive waste, parameters necessary for site selection will be acquired through deep drilling surveys from the basic survey stage. Unlike site investigations of rock mass structures such as tunnels and underground oil storage facilities, those related to the geological disposal of high-level radioactive waste are not only conducted in relatively deep depths, but also require a high level of quality control. In this report, based on the 750 m depth drilling experience conducted to acquire the parameters necessary for deep geological disposal, the methodology for deep drilling and the geology, geophysics, geochemistry, hydrogeology and rock mechanics obtained before, during, and after deep drilling are discussed. The procedures for multidisciplinary geoscientific investigations were briefly described. Regarding in-situ stress, one of the key evaluation parameter in the field of rock engineering, foreign and domestic cases related to the geological disposal of high-level radioactive waste were presented, and variations with depth were presented, and matters to be considered or agonized in acquiring evaluation parameters were mentioned.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2000.11a
• /
• pp.252-257
• /
• 2000

연구 결과를 간단히 요약하면 다음과 같다. 1) 온천 목적으로 개발된 국내 심부 암반 지하수(조사 대상 시료수 419개)는 화강암 및 화강편마암 지역에서 가장 높은 불소 함량을 보이며, 최소 75% 이상의 시료에서 먹는 물 수질 기준을 초과하였다. 2) 화강암 및 화강편마암 지역의 심부 지하수 내 불소 함량은 특히 Na-HCO$_3$ 유형의 지하수에서 높게 나타났는데, 이 유형의 지하수 수질은 사장석, 흑운모를 위시한 규산염 광물의 비조화 용해 반응에 의해 조절된다 이들 지하수는 비교적 깊은 관정심도를 나타내었다. 3) 백악기 화강암과 물과의 용출 반응 실험 결과, 전암 분말과의 반응에서는 최대 7 mg/l의 불소가, 흑운모의 용출 실험에서는 최대 35 mg/1의 불소가 용출되었다. 형석의 포화지수는 비교적 반응 초기에 침전 조건에 근접한 반면, 흑운모의 포화지수는 지속적으로 용해 조건에 놓여 있음을 확인하였다. 따라서, 국내 화강암 지역 심부 지하수 내의 불소는 대부분 흑운모의 비조화 용해 반응에 의해 용출되며, 용출 이후에는 형석의 용해/침전 평형 반응에 의해 그 농도가 조절되는 것으로 확인된다. 4) 앞으로, 보다 자세한 평형 열역학적 해석과 다른 이온종과의 상호 관계 규명 및 광물학적 검토를 통하여 불소의 기원과 거동에 관한 보다 정확한 해석을 시도할 계획이다.

• Tunnel and Underground Space
• /
• v.34 no.5
• /
• pp.477-502
• /
• 2024

To effectively dispose of high-level radioactive waste, it is crucial to understand the geological characteristics of the deep rock at the disposal site where the disposal facility will be located. Deep drilling is essential in this process and can obtain multidisciplinary deep rock characteristics by conducting tests using recovered cores and various tests using boreholes. However, in Korea, there are currently no established guidelines or procedures for deep drilling aimed at sit investigation and characterization for high-level radioactive waste disposal. This report proposes a deep drilling procedure based on five years from 2020 of multipurpose deep drilling experience conducted for various rock types by the Korea Institute of Geoscience and Mineral Resources. The proposed procedure includes various processes such as health, safety, and environments, pre-drilling work, drilling work, circulating drilling water management, site characterization evaluation parameter acquisition tests and measurements, and sampling. These procedures will need to be continuously revised and amended in the future to meet the needs of drilling and HLW disposal industries and related fields, as well as to strengthen quality assurance under the Nuclear Safety Act.

• Tunnel and Underground Space
• /
• v.33 no.5
• /
• pp.348-372
• /
• 2023

In relation to the high-level radioactive waste disposal project in deep fractured rock aquifer environments, it is essential to evaluate hydrogeological characteristics for evaluating the suitability of the site and operational stability. Such subsurface hydrogeological data is obtained through in-situ tests using boreholes excavated at the target site. The accuracy and reliability of the investigation results are directly related to the selection of appropriate test methods, the performance of the investigation system, standardization of the investigation procedure. In this report, we introduce the detailed procedures for the representative test method, the constant pressure injection test (CPIT), which is used to determine the key hydrogeological parameters of the subsurface fractured rock aquifer, namely hydraulic conductivity and storativity. This report further refines the standard test method suggested by the KSRM in 2022 and includes practical field application case conducted in volcanic rock aquifers where this investigation procedure has been applied.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.14 no.2
• /
• pp.179-188
• /
• 2016

Spent fuels from nuclear power plants, as well as high-level radioactive waste from the recycling of spent fuels, should be safely isolated from human environment for an extremely long time. Recently, meaningful studies on the development of deep borehole radioactive waste disposal system in 3-5 km depth have been carried out in USA and some countries in Europe, due to great advance in deep borehole drilling technology. In this paper, domestic deep geoenvironmental characteristics are preliminarily investigated to analyze the applicability of deep borehole disposal technology in Korea. To do this, state-of-the art technologies in USA and some countries in Europe are reviewed, and geological and geothermal data from the deep boreholes for geothermal usage are analyzed. Based on the results on the crystalline rock depth, the geothermal gradient and the spent fuel types generated in Korea, a preliminary deep borehole concept including disposal canister and sealing system, is suggested.

• Tunnel and Underground Space
• /
• v.15 no.6 s.59
• /
• pp.411-424
• /
• 2005

Weathering is defined as a process by which surface rock, once formed in the deep ground, is broken down and altered to keep the equilibrium with the ambient environment. In this study granitic rock samples of different weathering grades were collected in the field and the microscopic observation, X-ray diffraction analysis, electron microscopic observation, chemical analysis, and rock property tests were carried out. Formation of secondary minerals, especially clay minerals, by weathering was identified and the mechanism for the change of engineering properties such as rock strength degradation was analyzed. Tunnel model test, Failure behaviour, Shallow tunnel, Unsupproted tunnel length.

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