• Tunnel and Underground Space
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• v.33 no.6
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• pp.435-444
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• 2023

In the licensing application for the deep geological disposal system of high-level radioactive waste in Finland, the disposal tunnel backfilling has been changed from the block/pellet (for the construction) to the granular type (for the operation). Accordingly, for establishing the design concept for backfilling, it is necessary to examine applicability to the domestic facility through analyzing problems of the existing method and improvements in the alternative design. In this paper, we first reviewed the principal studies conducted for changing the backfill method in the licensing process of the Finnish facility, and identified the expected problems in applying the block/pellet backfill method. In addition, we derived the evaluation factors to be considered in terms of technical and operational aspects for the backfilling solution, and then conducted a comparative analysis for two types of backfill methods. This analysis confirmed the overall superiority of the design change. It is expected that these results could be utilized as the technical basis for deriving the optimum design plan in development process of the Korean-specific deep disposal facility. However, applicability should be reviewed in advance based on the latest technical data for the detailed evaluation factors that must be considered for selecting the backfilling method.

• Tunnel and Underground Space
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• v.33 no.6
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• pp.445-471
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• 2023

Long-term safety over millennia is the top priority consideration in the construction of disposal sites. However, ensuring the mechanical stability of deep geological repositories for spent fuel, a.k.a. radwaste, disposal during construction and operation is also crucial for safe operation of the repository. Imposing restrictions or limitations on tunnel support and lining materials such as shotcrete, concrete, grouting, which might compromise the sealing performance of backfill and buffer materials which are essential elements for the long-term safety of disposal sites, presents a highly challenging task for rock engineers and tunnelling experts. In this study, as part of an extensive exploration to aid in the proper selection of disposal sites, the anticipation of constructing a deep geological repository at a depth of 500 meters in an unknown state has been carried out. Through a review of 2D and 3D numerical analyses, the study aimed to explore the range of properties that ensure stability. Preliminary findings identified the potential range of rock properties that secure the stability of central and disposal tunnels, while the stability of the vertical tunnel network was confirmed through 3D analysis, outlining fundamental rock conditions necessary for the construction of disposal sites.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.1
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• pp.149-164
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• 2023

As part of the safety case development for generic disposal sites in Korea, it is necessary to develop generic assessment models using various geosphere-biosphere interfaces (GBIs) and potentially exposed groups (PEGs) that reflect the natural environmental characteristics and the lifestyles of people in Korea. In this study, a unique modeling strategy was developed to systematically construct and select Korean generic biosphere assessment models. The strategy includes three process steps (combination, screening, and experts' scoring) for the biosphere system conditions. First, various conditions, such as climate, topography, GBIs, and PEGs, were combined in the biosphere system. Second, the combined calculation cases were configured into interrelation matrices to screen out some calculation cases that were highly unlikely or less significant in terms of the exposure dose. Finally, the selected calculation cases were prioritized based on expert judgment by scoring the knowledge, probability, and importance. The results of this study can be implemented in the development of biosphere assessment models for Korean generic sites. It is believed that this systematic methodology for selecting the candidate calculation cases can contribute to increasing the confidence of future site-specific biosphere assessment models.

• Geophysics and Geophysical Exploration
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• v.27 no.1
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• pp.69-83
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• 2024

Considering importance and specificity, site investigations for deep geological disposal of Spent Nuclear Fuel require stringent quality control, unlike general geotechnical investigations for tunnels and bridges. In this study, we present a case of selecting geophysical survey method for individual site investigation stage and preparing geophysical survey guideline. The proposed geophysical survey guidelines include procedures, considerations, and quality control for exploration planning, data acquisition, data processing, and interpretation. They comprehensively summarize the contents of airborne electromagnetic survey and seismic reflection survey.

• Tunnel and Underground Space
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• v.30 no.2
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• pp.109-135
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• 2020

Globally, the deepening depth in the underground is a situation of the high interest for a purpose of the development of various facilities. The development of deep underground space should be based on the structural stability of rocks. Spalling is known to have an impact on the structural stability degradation in deep underground space. As an attempt to predict spalling, many researchers have proposed predicted conditions in accordance with stress states which occur around the tunnel, rock conditions, and types of rock. In addition, the analysis on spalling method has been verified by using computer modeling such as FLAC, EXAMINE, Insight 2D, UDEC and FRACOD, along with in-situ measurement results. In Canada URL (Underground Research Tunnel), CWFS model (Cohesion Weakening Frictional Strengthening) was used to precisely predict for the state of spalling, comparing spalling modeling. CWFS model has been identified as a reliable method for predicting such phenomena. This study aims to analyze several cases of spalling, and then make a comparison between the conditions for spalling occurrence and the predicted results of model CWFS. With this, it investigates the applicability of prediction of spalling, targeting pillar under deep depth condition.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.565-580
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• 2023

In this study, we reviewed and summarized comprehensive roles and importance of natural analogue studies for demonstrating the safety and improving the reliability of the safety for the deep geological disposal of high-level radioactive waste. We also investigated domestic and foreign status of natural analogue studies in order to study and substantiate complex and various radionuclide behaviors in subsurface disposal environments. In addition, we investigated and uranium behaviors in groundwater and rock in uranium deposits including domestic uranium deposits in Ogcheon Metamorphic Belt and biogeochemical interactions in geological environments. Although there are many limitations and uncertainties in directly using the information and data for uranium behaviors obtained from uranium deposits in the disposal safety assessment, the information and data can be utilized in the disposal safety assessment and safety case construction both in qualitative and partly quantitative ways.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.278-278
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• 2002

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.312.2-312
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• 1999

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.115-116
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• 2018

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.11a
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• pp.235-236
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• 2018