• Title, Summary, Keyword: deposition hole spacing

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Mechanical Stability Analysis of a High-Level Waste Repository for Determining Optimum Cavern and Deposition Hole Spacing (고준위폐기물 처분장의 최적 공동간격 및 처분공간격을 결정하기 위한 역학적 안정성 해석)

  • 박병윤;권상기
    • Tunnel and Underground Space
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    • v.10 no.2
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    • pp.237-248
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    • 2000
  • Based on the preliminary results from the therm analysis, which is currently carrying, three-dimensional computer simulations using a finite element code, ABAQUS Ver. 5.8, were designed to determine the mechanically stable cavern and deposition hole spacing. Linear elastic modeling for the cases with different cavern and deposition hole spacing were carried out under three different in situ stress conditions. From the simulations, the response of the rock to the stress redistribution after the excavation of the openings could be investigated. Also the optimum cavern and deposition hole spacing could be estimated based on the factor of safety. When the in situ stress determined from the actual stress measurements in Korea were used, the case with cavern spacing of 40m and deposition hole spacing of 3m was in very stable condition, because the factor of safety was calculated as 3.42., When the in situ stress conditions for Sweden and Canada were used, the previous case, they seem to be in stable condition, since the factors of safety are still higher than 1.0. From these results, it was concluded that the rock will not fail even after the stress redistribution.

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Optimization of the Layout of a Radioactive Waste Repository Based on Thermal Analysis (열해석에 기초한 방사성폐기물 처분장 배치 최적화)

  • Kwon Sangki;Choi Jong-Won;Cho Won-Jin
    • Tunnel and Underground Space
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    • v.14 no.6
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    • pp.429-439
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    • 2004
  • The deep underground High Level Waste (HLW) repository to dispose of 36,000tons of spent fuel from the reactors in Korea needs about $4km^2$ repository area. In this study, the deep undergrond repository layout was optimized to minimize the excavation rock volume as well as underground repository area. In the optimization, the results from thermal analysis were used to define the influence of tunnel and deposition hole spacings on repository layout. The repository area and excavation rock volume could be reduced with longer disposal tunnel length. When it is necessary to reduce the repository area with satisfying thermal criteria, it is better to reduce tunnel spacing and increase deposition hole spacing. In contrast, the excavation rock volume can be reduced by increasing the tunnel spacing and decreasing the hole spacing.

Structural Analysis for the Conceptual Design of a High Level Radioactive Waste Repository in a Deep Deposit (심지층 고준위 방사성 폐기물 처분장의 개념설계를 위한 구조적 안정성 해석)

  • 권상기;장근무;강철형
    • Tunnel and Underground Space
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    • v.9 no.2
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    • pp.102-113
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    • 1999
  • Two-dimensional and three-dimensional DEM programs, UDEC and 3DEC, were used to investigate the mechanical stability of the conceptual design of deposition drift and deposition holes constructed in a crystalline rock mass. From the simulations, the influence of discontinuities, the number of deposition holes, and deposition hole interval on the stability of deposition drift and deposition holes could be determined. From the two-dimensional and three-dimensional analysis. it was concluded that three-dimensional analysis should be carried 7ut fur deriving reliable conclusions. Even though the deposition hole interval changed from 8 m to 3 m, which did not damage the mechanical stability of the deposition drift.

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Comparative analysis of the magnetic and the transport properties of electron- and hole-doped manganite films

  • Kim, K.W.;Prokhorov, V.G.;Flis, V.S.;Park, J.S.;Eom, T.W.;Lee, Y.P.;Svetchnikov, V.L.
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.226-226
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    • 2010
  • Microstructure, magnetic and transport properties of as-deposited electron-doped $La_{1-x}Ce_xMnO_3$ and hole-doped $La_{1-x}Ce_xMnO_3$ films prepared by pulse laser deposition, with x = 0.1 and 0.3, have been investigated. The microstructural analysis reveals that the $La_{1-x}Ce_xMnO_3$ films have a column-like microstructure and a strip-domain phase with a periodic spacing of about 3c, which were not found for the $La_{1-x}Ce_xMnO_3$ ones. At the same time, the experimental results manifest that there is no fundamental difference in the magnetic and the transport properties between electron- and hole-doped manganite films, except the appearance of ferromagnetic response in the low-doped $La_{0.9}Ce_{0.1}MnO_3$ film at temperatures above the Curie point. The observed magnetic behavior, typical for the Griffiths-like phase, for this film is explained by the percolation mechanism of the ferromagnetic transition and by the presence of strip-domain phase which stimulates the magnetic phase separation.

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Three-Dimensional Modelling and Sensitivity Analysis for the Stability Assessment of Deep Underground Repository

  • Kwon, S.;Park, J.H.;Park, J.W.;Kang, C.H.
    • Nuclear Engineering and Technology
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    • v.33 no.6
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    • pp.605-618
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    • 2001
  • For the mechanical stability assessment of a deep underground high-level waste repository. computer simulations using FLAC3D were carried out and important parameters including stress ratio, depth, tunnel size, joint spacing, and joint properties were chosen from sensitivity analysis. The main effect as well as the interaction effect between the important parameters could be investigated effectively using fractional factorial design . In order to analyze the stability of the disposal tunnel and deposition hole in a discontinuous rock mass, different modelings were performed under different conditions using 3DEC and the influence of joint distribution and properties, rock properties and stress ratio could be determined. From the three dimensional modelings, it was concluded that the conceptual repository design was mechanically stable even in a discontinuous rock mass.

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Thermal-mechanical sensitivity analysis for the near-field of HLW repository (고준위 폐기물 처분장 near-field에 대한 열-역학적 민감도 분석)

  • 권상기;최종원;강철형
    • Tunnel and Underground Space
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    • v.13 no.2
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    • pp.138-152
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    • 2003
  • Three-dimensional computer modeling using FLAC3D had been carried out fur evaluating the thermal-mechanical stability of a high-level radioactive waste repository excavated in several hundred deep location. For effective modeling, a FISH program was made and the geological conditions and rock properties achieved from the drilling sites in Kosung and Yusung areas were used. Sensitivity analysis fer the stresses and temperatures from the modeling designed utilizing fractional factorial design was carried out. From the sensitivity analysis, the important design parameters and their interactions could be determined. From this study, it was found that deposition hole spacing is the most important parameter on the thermal and mechanical stability. The second and third most important parameters were disposal tunnel and buffer thickness.

An Analysis of the Deep Geological Disposal Concepts Considering Spent Fuel Rods Consolidation (사용후핵연료봉 밀집을 고려한 심지층처분 개념 분석)

  • Lee, Jongyoul;Kim, Hyeona;Lee, Minsoo;Kim, Geonyoung;Choi, Heuijoo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.12 no.4
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    • pp.287-297
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    • 2014
  • For several decades, many countries operating nuclear power plants have been studying the various disposal alternatives to dispose of the spent nuclear fuel or high-level radioactive waste safely. In this paper, as a direct disposal of spent nuclear fuels for deep geological disposal concept, the rod consolidation from spent fuel assembly for the disposal efficiency was considered and analyzed. To do this, a concept of spent fuel rod consolidation was described and the related concepts of disposal canister and disposal system were reviewed. With these concepts, several thermal analyses were carried out to determine whether the most important requirement of the temperature limit for a buffer material was satisfiedin designing an engineered barrier of a deep geological disposal system. Based on the results of thermal analyses, the deposition hole distance, disposal tunnel spacing and heat release area of a disposal canister were reviewed. And the unit disposal areas for each case were calculated and the disposal efficiencies were evaluated. This evaluation showed that the rod consolidation of spent nuclear fuel had no advantages in terms of disposal efficiency. In addition, the cooling time of spent nuclear fuels from nuclear power plant were reviewed. It showed that the disposal efficiency for the consolidated spent fuel rods could be improved in the case that cooling time was 70 years or more. But, the integrity of fuels and other conditions due to the longer term storage before disposal should be analyzed.