• Title, Summary, Keyword: Geological repository

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An Approach to Improve Romanian Geological Repository Planning

  • Andrei, Veronica;Prisecaru, Ilie
    • Nuclear Engineering and Technology
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    • v.48 no.2
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    • pp.495-504
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    • 2016
  • International standards recommend typical phases to be included within any national program for the development of a geological repository dedicated to disposal of the high level radioactive wastes generated in countries using nuclear power. However, these are not universally applicable and the content of each of these phases may need to be adapted for each national situation and regulatory and institutional framework. Several national geological repository programs have faced failures in schedules and have revised their programs to consider an adapted phased management approach. The authors have observed that in the case of those countries in the early phases of a geological repository program where boundary conditions have not been fully defined, international recommendations for handling delays/failures in the national program might not immediately help. This paper considers a case study of the influences of the national context risks on the current planning schedule of the Romanian national geological repository. It proposes an optimum solution for an integrated response to any significant adverse impact arising from these risks, enabling sustainable program planning.

Analysis of Siting Criteria of Overseas Geological Repository (I): Geology (국외 심지층 처분장 부지선정기준 분석 (I) : 지질)

  • Jung, Haeryong;Kim, Hyun-Joo;Kim, Min Jung;Cheong, Jae-Yeol;Jeong, Yi-Yeong;Lee, Eun Yong
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.10 no.4
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    • pp.305-311
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    • 2012
  • Geology, hydrogeology, and geochemistry are the main technical siting factors of a geological repository for spent nuclear fuels. This paper focused on how rock's different geological conditions, such as topography, soils, rock types, structural geology, and geological events, influence the functions of the geological repository. In the context, the site selection criteria of various countries were analyzed with respect to the geological conditions. Each country established the criteria based on its important geological backgrounds. For example, it was necessary for Sweden to take into account the effect of ice age on the land uplift and sea level change, whereas Japan defined seismic activity and volcanism as the main siting factors of the geological repository. Therefore, the results of the paper seems to be helpful in preparing the siting criteria of geological repository in Korea.

Comparison of proliferation resistance among natural uranium, thorium-uranium, and thorium-plutonium fuels used in CANada Deuterium Uranium in deep geological repository by combining multiattribute utility analysis with transport model

  • Nagasaki, Shinya;Wang, Xiaopan;Buijs, Adriaan
    • Nuclear Engineering and Technology
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    • v.50 no.5
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    • pp.794-800
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    • 2018
  • The proliferation resistance (PR) of Th/U and Th/Pu fuels used in CANada Deuterium Uranium for the deep geological repository was assessed by combining the multiattribute utility analysis proposed by Chirayath et al., 2015 with the transport model of radionuclides in the repository and comparing with that of the used natural U fuel case. It was found that there was no significant advantage for Th/U and Th/Pu fuels from the viewpoint of the PR in the repository. It was also found that the PR values for used nuclear fuels in the repository of Th/U, Th/Pu, and natural U was comparable with those for enrichment and reprocessing facilities in the pressurized water reactor (PWR) nuclear fuel cycle. On the other hand, the PR values considering the transport of radionuclides in the repository were found to be slightly smaller than those without their transport after the used nuclear fuels started dissolving after 1,000 years.

Thermal Analysis of High Level Radioactive Waste Repository Using a Large Model

  • Park, Jeong-Hwa;Kuh, Jung-Eui;Sangki Kwon;Kang, Chul-Hyung
    • Nuclear Engineering and Technology
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    • v.32 no.3
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    • pp.244-253
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    • 2000
  • A Simple Large Model (SLM), which can be used to make thermal calculation for a deep geological repository with finite number of HLW canisters, was developed. In order to develop the SLM, a Simple Basic Model (SBM), which will be a unit of the SLM, was optimized first. The SBM was optimized to achieve the same maximum buffer temperature as that of the Detailed Basic Model (DBM) representing the real geometric aspects of the repository. In contrast to the models with the assumption of infinite number of canisters which cannot consider boundary effect, the SLM can model the real repository with finite number of canisters and thus consider the boundary effect. Thermal results from the SLM can be used to evaluate the reliability of the models, which do not consider boundary effect. This model can also be used to simulate the thermal layout design and to analyze the thermal safety of a deep geological repository as well as an underground laboratory.

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Emplacement Process of the HLW in the Deep Geological Repository (지하처분장에서의 고준위폐기물 처분공정 개념)

  • 이종열;김성기;조동건;최희주;최종원
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1013-1016
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    • 2004
  • High level radioactive wastes, such as spent fuels generated from nuclear power plant, will be disposed in a deep geological repository. To maintain the integrity of the disposal canister and to carry out the process effectively, the emplacement process for the canister system in borehole of disposal tunnel should be well defined. In this study, the concept of the disposal canister emplacement process for deep geological disposal was established. To do this, the spent fuel arisings and disposal rate were reviewed. Also, not only design requirements, such canister and disposal depth but also preliminary repository layout concept were reviewed. Based on the requirements and the other bases, the canister emplacement process in the borehole of the disposal tunnel was established. The established concept of the disposal canister emplacement process will be improved continuously with the future studies. And this concept can be effectively used in implementing the reference repository system of our own case.

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A Study on the Prediction of HLW Temperature from Natural Ventilation Quantity using CFD (전산유체학을 이용한 고준위 방사성 폐기물 처분장의 자연환기량에 의한 온도예측)

  • Roh, Jang-Hoon;Yu, Yeong-Seok;Jang, Seung-Hyun;Park, Seon-Oh;Kim, Jin
    • Tunnel and Underground Space
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    • v.22 no.6
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    • pp.429-437
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    • 2012
  • This study predicted temperature in the disposal tunnels using computational fluid dynamics based on natural ventilation quantity that comes from high altitude and temperature differences that are the characteristics of high level waste repository. The result of the previous study that evaluated quantitatively natural ventilation quantity using a hydrostatic method and CFD shows that significant natural ventilation quantity is generated. From the result, this study performed the prediction of temperature in disposal tunnels by natural ventilation quantity by the caloric values of the wastes, at both deep geological repository and surface repository. The result of analysis shows that deep geological repository is effective for thermal control in the disposal tunnels due to heat transfer to rock and the generation of sufficient natural ventilation quantity, while surface repository was detrimental to thermal control, because surface repository was strongly affected by external temperature, and could not generate sufficient natural ventilation quantity. Moreover, this study found that in the case of deep geological repository with a depth of 200 m, the heatof about $10^{\circ}C$ was transferred to the depth of 500 m. Thus, it is considered that if the high level waste repository scheduled to be built in the country is designed placing an emphasis on thermal control, deep geological repository rather than surface repository is more appropriate.

Validation of Performance of Engineered Barriers in a Geological Repository: Review of In-Situ Experimental Approach (심지층처분장 공학적방벽 성능 실증: 현장실험적 접근법 검토)

  • Cho, Won-Jin;Kim, Geon Young
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.16 no.2
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    • pp.137-164
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    • 2018
  • The guarantee of the performance of the engineered barriers in a geological repository is very important for the long-term safety of disposal as well as the efficient design of the repository. Therefore, the performance of the engineered barriers under repository condition should be demonstrated by in-situ experiments conducted in an underground research laboratory. This article provides a review of the major in-situ experiments that have been carried out over the past several decades at underground research laboratories around the world to validate the performance of engineered barriers of a repository, as well as their results. In-situ experiments to study the coupled thermal-hydraulic-mechanical behavior of the engineered barrier system used to simulate the post-closure performance of the repository are analyzed as a priority. In addition, in-situ experiments to investigate the performance of the buffer material under a real repository environment have been reviewed. State-of-the art in-situ validations of the buffer-concrete interaction, and the installation of the buffer, backfill and plug, as well as characterization of the near-field rock and the corrosion of the canister materials are, also performed.

Change of Fractured Rock Permeability due to Thermo-Mechanical Loading of a Deep Geological Repository for Nuclear Waste - a Study on a Candidate Site in Forsmark, Sweden

  • Min, Ki-Bok;Stephansson, Ove
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.187-187
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    • 2009
  • Opening of fractures induced by shear dilation or normal deformation can be a significant source of fracture permeability change in fractured rock, which is important for the performance assessment of geological repositories for spent nuclear fuel. As the repository generates heat and later cools the fluid-carrying ability of the rocks becomes a dynamic variable during the lifespan of the repository. Heating causes expansion of the rock close to the repository and, at the same time, contraction close to the surface. During the cooling phase of the repository, the opposite takes place. Heating and cooling together with the, virgin stress can induce shear dilation of fractures and deformation zones and change the flow field around the repository. The objectives of this work are to examine the contribution of thermal stress to the shear slip of fracture in mid- and far-field around a KBS-3 type of repository and to investigate the effect of evolution of stress on the rock mass permeability. In the first part of this study, zones of fracture shear slip were examined by conducting a three-dimensional, thermo-mechanical analysis of a spent fuel repository model in the size of 2 km $\times$ 2 km $\times$ 800 m. Stress evolutions of importance for fracture shear slip are: (1) comparatively high horizontal compressive thermal stress at the repository level, (2) generation of vertical tensile thermal stress right above the repository, (3) horizontal tensile stress near the surface, which can induce tensile failure, and generation of shear stresses at the comers of the repository. In the second part of the study, fracture data from Forsmark, Sweden is used to establish fracture network models (DFN). Stress paths obtained from the thermo-mechanical analysis were used as boundary conditions in DFN-DEM (Discrete Element Method) analysis of six DFN models at the repository level. Increases of permeability up to a factor of four were observed during thermal loading history and shear dilation of fractures was not recovered after cooling of the repository. An understanding of the stress path and potential areas of slip induced shear dilation and related permeability changes during the lifetime of a repository for spent nuclear fuel is of utmost importance for analysing long-term safety. The result of this study will assist in identifying critical areas around a repository where fracture shear slip is likely to develop. The presentation also includes a brief introduction to the ongoing site investigation on two candidate sites for geological repository in Sweden.

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Analysis of the Disposal Tunnel and Disposal Pit Spacing for the Spent Fuel Repository Layout (사용후핵연료 지하 처분장 배치를 위한 처분공 및 처분터널 간격 분석)

  • Lee, Jong-Youl;Lee, Yang;Choi, Heui-Joo;Choi, Jong-Won
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.4 no.4
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    • pp.393-400
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    • 2006
  • In design of a deep geological repository for the high level wastes, it is very important that the temperature of the bentonite block should not be over $100^{\circ}C$ to maintain the integrity of the bentonite buffer block from the decay heat. In this study, for the layout of the repository to meet the requirement, the analysis of the disposal tunnel and disposal pit spacing was carried out. To do this, based on the reference repository concept, several cases of cooling times and disposal tunnel and disposal pit spacing were compared. The thermal stabilities of the disposal systems were analyzed in terms of the cooling time and spacing. The results showed that it was more desirable to determine the layout of the repository in terms of disposal pit spacing than the disposal tunnel spacing. The results of these analyses can be used in the deep geological repository design. The detailed analyses with the exact site characteristics data will reduce the uncertainty of the results.

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Reference Spent Fuel and Its Characteristics for a Deep Geological Repository Concept Development

  • Choi, Jong-Won;Ko, Won-Il;Kang, Chul-Hyung
    • Nuclear Engineering and Technology
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    • v.31 no.6
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    • pp.23-38
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    • 1999
  • This study addresses the reference spent fuel and its characteristics for developing a geological repository concept. As a disposal capacity of the reference repository system to be developed, spent fuel inventories were projected based on the basis of the Nuclear Energy Plan of the Long-term National Power Program. The reference spent fuel encompassing a variability in characteristics of all existing and future spent fuels of interest was defined. Key parameters in the reference fuel screening processes were the nuclear and mechanical design parameters and the burnup histories for existing spent fuels as of 1996 and for future spent fuels with the more extended burnup the initial enrichment and its expected turnup. The selected reference fuel was characterized in terms of initial enrichment, bumup, dimension, gross weight and age. Also the isotopic composition and the radiological properties are quantitatively identified. This information provided in this study could be used as input for repository system development and performance assessment and applied in fuel material balance evaluation for the various types of back-end fuel cycle studies.

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