• Title, Summary, Keyword: High-level waste HLW

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THE IMPACT OF FUEL CYCLE OPTIONS ON THE SPACE REQUIREMENTS OF A HLW REPOSITORY

  • Kawata, Tomio
    • 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.

Longevity Issues in Swelling Clay as a Buffer Material for a HLW Repository (고준위폐기물처분장 완충재물질로서 팽윤성 점토의 장기건전성과 주요 고려사항)

  • Lee, Jae-Owan;Cho, Won-Jin
    • 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.

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Chinese buffer material for high-level radiawaste disposal --Basic features of GMZ-l

  • WEN Zhijian
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.236-244
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    • 2005
  • Radioactive wastes arising from a wide range of human activities are in many different physical and chemical forms, contaminated with varying radioactivity. Their common feature is the potential hazard associated with their radioactivity and the need to manage them in such a way as to protect the human environment. The geological disposal is regarded as the most reasonable and effective way to safely disposal high-level radioactive wastes in the world. The conceptual model of geological disposal in China is based on a multi-barrier system that combines an isolating geological environment with an engineered barrier system. The buffer is one of the main engineered barriers for HLW repository. The buffer material is expected to maintain its low water permeability, self-sealing property, radio nuclides adsorption and retardation property, thermal conductivity, chemical buffering property, overpack supporting property, stress buffering property over a long period of time. Benotite is selected as the main content of buffer material that can satisfy above. GMZ deposit is selected as the candidate supplier for Chinese buffer material of High Level Radioactive waste repository. This paper presents geological features of GMZ deposit and basic property of GMZ Na bentonite. GMZ bentonite deposit is a super large scale deposits with high content of Montmorillonite (about $75\%$) and GMZ-l, which is Na-bentonite produced from GMZ deposit is selected as reference material for Chinese buffer material study.

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Implementation of the strain hardening model into buffer material in high level waste repository

  • Chen, Lu;Qiao, Lan;Cui, Ming;Li, Qingwen
    • Geosciences Journal
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    • v.21 no.2
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    • pp.277-289
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    • 2017
  • Engineered Barrier System (EBS) primarily provides a protective cover for the High Level Waste (HLW) canisters. In addition, it functions as an efficient hydraulic and chemical barrier system. For in situ disposal applications, the ideal buffer material is bentonite and it is fabricated into blocks to build EBS. Currently, traditional methods introduce significant errors in constitutive modeling of those modeled blocks. In this paper, the particular failure laws and stress-strain laws of bentonite blocks were furnished from a lot of uniaxial and triaxial tests. Also, it showed that the stress-strain relations given by the traditional constitutive relations did not correspond to the failure forms of bentonite specimens in the experiments. On this basis, the relations between internal friction angle, cohesion and plastic strain were analyzed so that a new strain hardening model was established under the framework of Mohr-Coulomb criterion. In the end, a series of 3D computation of HLW disposal were carried out using the software FLAC3D, where the proposed strain hardening model led to satisfactory prediction of the buffer materials.

In Situ Experiments for the Development of High-level Radioactive Waste Disposal Techniques at Underground Research Laboratories in Foreign Countries (고준위방사성폐기물 처분 기술개발을 위한 세계 각국 지하연구시설에서의 현장시험)

  • Kwon, Sangki;Kim, Hyung-Mok
    • Journal of the Korean Society of Mineral and Energy Resources Engineers
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    • v.54 no.4
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    • pp.328-343
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    • 2017
  • It is an urgent issue to develop methods for the safe management of the high-level radioactive waste(HLW) produced from the operation of nuclear facilities for sustainable utilization of nuclear energy. In the countries utilizing nuclear energy, underground research laboratories(URLs) were constructed and operated for the development of HLW disposal technique. In this study, a literature survey was carried out for summarizing the status of URLs in the foreign countries and in situ experiments carried out at the URLs.

Two-Dimensional Nuclide Transport Around a HLW Repository

  • Lee, Youn-Myoung;Kang, Chul-Hyung;Hwang, Yong-Soo;Chun, Kwan-Sik
    • Nuclear Engineering and Technology
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    • v.31 no.4
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    • pp.432-443
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    • 1999
  • Using a two-dimensional numerical model, nuclide transport in the buffer between the canister and adjacent rock in a high-level radioactive waste repository is dealt with. Calculations are made for a typical case with a three-member decay chain, $^{234}$ U longrightarrow $^{230}$ Th longrightarrow $^{226}$ Ra. The solution method used here is based on a physically exact formulation by a control volume method directly integrating the governing equation over each control volume.

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Thermal-hydro-mechanical Properties of Reference Bentonite Buffer for a Korean HLW Repository (우리나라 고준위폐기물처분장 기준벤토나이트완충재의 열-수리-역학적 특성치)

  • Lee, Jae-Owan;Cho, Won-Jin;Kwon, Sang-Ki
    • Tunnel and Underground Space
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    • v.21 no.4
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    • pp.264-273
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    • 2011
  • Bentonite buffer is one of the major components of an engineered barrier for an HLW (High-Level Waste) repository. The bentonite buffer is significantly exposed to the decay heat from radioactive wastes, the inflow of groundwater from the surrounding rock of the repository, and the high swelling pressure of densely-compacted bentonite that comes in contact with the groundwater. Therefore, it is essential to understand the THM (Thermal-Hydro-Mechanical) behavior of the bentonite buffer and to acquire the input data of its related constitutive models for the performance and safety assessment of an HLW repository. This paper analyzed the THM properties which have been obtained by conducting laboratory tests with a candidate buffer material for a Korean HLW repository. Moreover the formulation recipe of the reference bentonite buffer was defined on the basis of functional criteria, thus suggesting the THM properties which correspond to the formulation recipe of the reference bentonite buffer.

The Hydrogeological Conditions in the Granitic Area for the Research Program of HLW Disposal in Korea

  • Kim, Chunsoo;Daeseok Bae;Kim, Kyungsu;Yongkwon Koh;Kim, Geonyoung
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.51-59
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    • 2004
  • The geological research as a part of HLW disposal program in Korea is carried out to provide necessary data for the establishment of the reference repository system in term of design and safety assessment in the crystalline rock terrains. Six deep boreholes were drilled to obtain hydrogeological and hydrochemical data from Jurassic granites in the Yuseong area, Korea. The core observation, televiewer logging and hydraulic testing were carried out during and after drilling and multi-packer system were installed in the boreholes of 500m depth for hydraulic and hydrochemical monitoring including environmental isotopes. The integration of hydrogeochemical and hydrodynamic data would be built greater confidence for the understanding of groundwater system in fractured rock mass. This geoscientific program could be possible to suggest a general guideline to develop the reference disposal concept of high-level radioactive waste in Korea.

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Engineering-scale Test for Validating the T-H-M Behavior of a HLW Repository: Experimental Set-up

  • Lee, Jae-Owan;Baik, Min-Hoon;Cho, Won-Jin
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.194-198
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    • 2004
  • The thermo-hydro-mechanical (T-H-M) process is one of major issues in the performance assessment of a high level waste (HLW) repository. An engineering-scale test was planned and its experimental set-up has being installed, to validate the T-H-M behavior in the buffer of a reference disposal system. The experimental set-up consists of 4 major components: the confining cylinder with its hydration water tank, the bentonite block, the heating system, and the sensors and instruments. The monitoring and data acquisition system is employed to control the heater to maintain the temperature of $95^{\circ}C$ at the interface of the heater and bentonite blocks and to collect signals from sensors and instruments installed in the bentonite blocks.

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Post Closure Long Term Safely of the Initial Container Failure Scenario for a Potential HLW Repository (고준위 방사성폐기물 처분장 불량 용기 발생 시나리오에 대한 폐쇄후 장기 방사선적 안전성 평가)

  • 황용수;서은진;이연명;강철형
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.2 no.2
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    • pp.105-112
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    • 2004
  • A waste container, one of the key components of a multi-barrier system in a potential high level radioactive waste (HLW) repository in Korea ensures the mechanical stability against the lithostatic pressure of a deep geologic medium and the swelling pressure of the bentonite buffer. Also, it delays potential release of radionuclides for a certain period of time, before it is corroded by intruding impurities. Even though the material of a waste container is carefully chosen and its manufacturing processes are under quality assurance processes, there is a possibility of initial defects in a waste container during manufacturing. Also, during the deposition of a waste container in a repository, there is a chance of an incident affecting the integrity of a waste container. In this study, the appropriate Features, Events, and Processes(FEP's) to describe these incidents and the associated scenario on radionuclide release from a container to the biosphere are developed. Then the total system performance assessment on the Initial waste Container Failure (ICF) scenario was carried out by the MASCOT-K, one of the probabilistic safety assessment tools KAERI has developed. Results show that for the data set used in this paper, the annual individual dose for the ICF scenario meets the Korean regulation on the post closure radiological safety of a repository.

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