• Tunnel and Underground Space
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• v.30 no.2
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• pp.136-148
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• 2020

Nuclear power plants have been operated in Korea since 1978, thus the high-level radioactive waste (HLW) produced from the plants has been accumulated accordingly. Hence, it is urgent to secure a final repository for HLW disposal, however, siting process should be preceded, which usually takes long time, as it requires broad and precise investigation. The investigation is generally carried out in stages, which consists of multidisciplinary approaches. In this study, the case studies mainly pertaining to rock mechanics were conducted. Rock mechanical aspects required in each stage and their applications were investigated and corresponding R&D researches were presented as well. At the same time, current research status in Korea was presented, followed by a brief future research plan with regard to the site investigation. The future research aims to produce fundamental information for siting process, and the compiled cases in this study will be utilized as references in the research.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4083-4095
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• 2023

Currently, various research institutes in Korea are conducting research to develop a safety case for deep geological repository for high-level radioactive waste (HLW). In the past, low and intermediate-level waste (LILW) was approved by a regulatory body by performing a post-closure safety assessment, but HLW has different disposal characteristics and safety objectives are different. Therefore, in the case of HLW, safety assessment should be performed based on these changed conditions, and specific procedures are also under development. In this paper, the regulatory status of prior research institutes, feature, event and process (FEP) and scenario development cases were investigated for well-organized FEP and scenario development methodologies. In addition, through the results of these surveys, the requirements and procedures necessary for the FEP and scenario development stage during the safety assessment of repository for HLW were presented. These review results are expected to be used to identify the overall status of previous studies in conducting post-closure risk assessment for HLW repository, starting with identifying regulatory requirements, the most basic element.

• Nuclear Engineering and Technology
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• v.39 no.6
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• pp.683-690
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• 2007

Because of increasing concerns regarding global warming and the longevity of oil and gas reserves, the importance of nuclear energy as a major source of sustainable energy is gaining recognition worldwide. To make nuclear energy truly sustainable, it is necessary to ensure not only the sustainability of the fuel supply but also the sustained availability of waste repositories, especially those for high-level radioactive waste (HLW). From this perspective, the effort to maximize the waste loading density in a given repository is important for easing repository capacity problems. In most cases, the loading of a repository is controlled by the decay heat of the emplaced waste. In this paper, a comparison of the decay heat characteristics of HLW is made among the various fuel cycle options. It is suggested that, for a future fast breeder reactor (FBR) cycle, the removal and burning of minor actinides (MA) would significantly reduce the heat load in waste and would allow for a reduction of repository size by half.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.1
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• pp.55-63
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• 2008

A swelling clay should remain physically and chemically stable for a long time to perform its functions as a buffer material of a high-level waste (HLW) repository. The longevity issues in the swelling clay were reviewed to evaluate their importance in the performance of a repository. The review results suggest that an elevated temperature due to decay heat, groundwater chemistry, high pH environment by concrete, organic matter and microbes, radiation, and mechanical disturbance might significantly affect the long-term performance of a swelling clay as a buffer material. This paper will be used as basic informations to design the swelling clay buffer for a HLW repository.

• Journal of Radiation Protection and Research
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• v.26 no.2
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• pp.119-132
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• 2001

This paper provides the basic technical and safety criteria to guide establishing the reference HLW geological repository system that has been developing based on the recommendations from the international organizations such as IAEA and ICRP as well as the comparison of the regulations of several leading countries in HLW disposal. The proposed criteria and guidelines were categorized by the basic principles and general criteria for the radiological safety and the functional criteria of the repository system components. They would be useful for the development of the national regulations and criteria for HLW disposal in the future. They, of course, will be revised based on the deep geological investigation in Korean Peninsular which will be implemented in the future.

• Nuclear Engineering and Technology
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• v.38 no.6
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• pp.489-504
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• 2006

A review has been made for the previous studies on safety of a geologic repository for high-level radioactive wastes (HLW) related to autocatalytic criticality phenomena with positive reactivity feedback. Neutronic studies on geometric and materials configuration consisting of rock, water and thermally fissile materials and the radionuclide migration and accumulation studies were performed previously for the Yucca Mountain Repository and a hypothetical water-saturated repository for vitrified HLW. In either case, it was concluded that it would be highly unlikely for an autocatalytic criticality event to happen at a geologic repository. Remaining scenarios can be avoided by careful selection of a repository site, engineered-barrier design and conditioning of solidified HLW. Thus, criticality safety should be properly addressed in regulations and site selection criteria. The models developed for radiological safety assessment to obtain conservatively overestimated exposure dose rates to the public may not be used directly for the criticality safety assessment, where accumulated fissile materials mass needs to be conservatively overestimated. The models for criticality safety also require more careful treatment of geometry and heterogeneity in transport paths because a minimum critical mass is sensitive to geometry of fissile materials accumulation.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.329-337
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• 2005

Synroc which comprises hollandite-rich ($Ba_{1-x}Cs_{2x}\;(Al_yTi_{2-y})\;Ti_{6}O_{16},\;75wt\%$), perovskite ($Ca_{1-x}Sr_xTiO_3,\;15wt\%$) and rutile ($TiO_2,\;10wt\%$) is devised for the immobilization of Sr/Cs (1:3, wt$\%$) separated from HLW liquid. Especially, hollandite-rich Synroc with different contents of Al element is fabricated, and its mineral phase assemblage and microstructure are determined by using XRD and SEM/EDS. The durability test is carried out by using MCC-1 method, leachate is analyzed by using ICP/MS and ICP/ AES. The results indicate that hollandite-rich Synroc variants is a suitable host for Immobilization of Sr/Cs separated from HLW liquid.

• Nuclear Engineering and Technology
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• v.34 no.4
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• pp.406-414
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• 2002

In TSPA of long-term post closure radiological safety on permanent disposal of HLW in Korea, appropriate management of input and output data through QA is necessary. The robust QA system is developed using the T2R3 principles applicable for five major steps in R&D＇s. The proposed system is implemented in the web-based system so that all participants in TSPA are able to access the system. In addition, the internet based input database for TSPA is developed. Currently data from literature surveys, domestic laboratory and field experiments as well as expert elicitation are applied for TSPA.

• Economic and Environmental Geology
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• v.55 no.1
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• pp.1-17
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• 2022

The mechanical and thermal properties of the rock masses can affect the performance associated with both the isolating and retarding capacities of radioactive materials within the deep geological disposal system for High-Level Radioactive Waste (HLW). In this study, the essential parameters for the site descriptive model (SDM) related to the rock mechanics and thermal properties of the HLW disposal facilities site were reviewed, and the technical background was explored through the cases of the preceding site descriptive models developed by SKB (Swedish Nuclear and Fuel Management Company), Sweden and Posiva, Finland. SKB and Posiva studied parameters essential for the investigation and evaluation of mechanical and thermal properties, and derived a rock mechanics site descriptive model for safety evaluation and construction of the HLW disposal facilities. The rock mechanics SDM includes the results obtained from investigation and evaluation of the strength and deformability of intact rocks, fractures, and fractured rock masses, as well as the geometry of large-scaled deformation zones, the small-scaled fracture network system, thermal properties of rocks, and the in situ stress distribution of the disposal site. In addition, the site descriptive model should provide the sensitivity analysis results for the input parameters, and present the results obtained from evaluation of uncertainty.

• Tunnel and Underground Space
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• v.4 no.3
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• pp.256-260
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• 1994

HLW canister array was designed by FLLSSM program, considering the thermal concentration. Rock properties were chosen as those of granite, the most possible bedrock for the repository in Korea. It was shown that repository area and excavation volumes can be determined by the pitch or distance between canisters. Pitch can be reduced to 0.6 m assuming the tolerance temperature as 200$^{\circ}C$. Thermal concentration was reduced as storage time for cooling the canister passed. After 10 years of storage the thermal problems seemed to be negligible.