• 방사성폐기물학회지
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• 제16권2호
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• pp.137-164
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• 2018

심지층처분장 공학적방벽의 성능 보장은 장기처분안전성 측면에서 뿐만 아니라 심지층처분장의 효율적인 설계를 위해서도 매우 중요하다. 따라서 지하실험시설에서 수행되는 현장실험들을 통해 심지층처분장 조건 하에서의 공학적방벽 성능을 입증할 필요가 있다. 이 논문에서는 심지층처분장 공학적방벽의 성능을 실증하기 위해, 지난 수십 년 동안 전 세계에서 수행되어온 주요 현장실험의 현황과 그 결과에 대해 검토하였다. 먼저 심지층처분장의 폐쇄 후 성능을 모사하는 공학적방벽시스템의 열-수리-역학적 복합거동을 규명하기 위한 현장실험들이 분석되었다. 아울러 실제 심지층처분장의 환경에서 완충재의 성능을 조사하기 위한 현장실험들이 검토되었다. 완충재-콘크리트 상호반응, 완충재, 뒷채움재 및 플러그의 설치, 그리고 근계암반 특성과 처분용기 재질의 부식 현상을 규명하기 위한 현장실험들의 기술현황도 분석되었다.

• 한국전기전자재료학회논문지
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• 제22권1호
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• pp.17-21
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• 2009

The electrical characteristics of band-gap engineered tunneling barriers consisting of thin $SiO_2$ and $Si_3N_4$ dielectric layers were investigated for nonvolatile memory device applications. The band structure of band-gap engineered tunneling barriers was studied and the effectiveness of these tunneling barriers was compared with the conventional tunneling $SiO_2$ barrier. The band-gap engineered tunneling barriers composed of thin $SiO_2$ and $Si_3N_4$ layers showed a lower operation voltage, faster speed and longer retention time than the conventional $SiO_2$ tunnel barrier. The thickness of each $SiO_2$ and $Si_3N_4$ layer was optimized to improve the performance of non-volatile memory.

• Nuclear Engineering and Technology
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• 제45권1호
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• pp.41-52
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• 2013

Adequate design of engineered barriers, including canister, buffer and backfill, is important for the safe disposal of high-level radioactive waste. Three-dimensional computer simulations were carried out under different condition to examine the thermal and mechanical behavior of engineered barriers and rock mass. The research looked at five areas of importance, the effect of the swelling pressure, water content of buffer, density of compacted bentonite, emplacement type and the selection of failure criteria. The results highlighted the need to consider tensile stress in the outer shell of a canister due to thermal expansion of the canister and the swelling pressure from the buffer for a more reliable design of an underground repository system. In addition, an adequate failure criterion should be used for the buffer and backfill.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.189-190
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• 2008

The electrical characteristics of band-gap engineered tunneling barriers consisting of thin $SiO_2$ and $Si_3N_4$ dielectric layers were investigated. The band structure of stacked tunneling barriers was studied and the effectiveness of these tunneling barriers was compared with that of the conventional tunneling barrier. The band-gap engineered tunneling barriers show the lower operation voltage, faster speed and longer retention time than the conventional $SiO_2$ tunnel barrier. The thickness of each $SiO_2$ and $Si_3N_4$ layer was optimized to improve the performance of non-volatile memory.

• 한국전기전자재료학회논문지
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• 제22권5호
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• pp.386-389
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• 2009

The electrical characteristics and annealing effects of tunneling dielectrics stacked with $SiO_2$ and $Si_{3}N_{4}$ were investigated. I-V characteristics of band gap engineered tunneling gate stacks consisted of $Si_{3}N_{4}/SiO_2/Si_{3}N_{4}$ (NON), $SiO_2/Si_{3}N_{4}/SiO_2$ (ONO) dielectrics were evaluated and compared with $SiO_2$ single layer using the MOS (metal-oxide-semiconductor) capacitor structure. The leakage currents of engineered tunneling barriers (ONO, NON stacks) are lower than that of the conventional $SiO_2$ single layer at low electrical field. Meanwhile, the engineered tunneling barriers have larger tunneling current at high electrical field. Furthermore, the increased tunneling current through engineered tunneling barriers related to high speed operation can be achieved by annealing processes.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.128-129
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• 2008

The annealing effects of $SiO_2/Si_3N_4$ stacked tunneling dielectrics were investigated. I-V characteristics of band gap engineered tunneling gate stacks consisted of $Si_3N_4/SiO_2/Si_3N_4$(NON), $SiO_2/Si_3N_4/SiO_2$(ONO) dielectrics were evaluated and compared with $SiO_2$ single layer using the MOS(Metal-Oxide-Semiconductor) capacitor structure. The leakage currents of engineered tunneling barriers (ONO, NON stacks) are lower than that of the conventional $SiO_2$ single layer at low electrical field. Meanwhile, the engineered tunneling barriers have larger tunneling current at high electrical field and improved electrical characteristics by annealing processes than $SiO_2$ layer.

• 방사성폐기물학회지
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• 제20권4호
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• pp.469-488
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• 2022

Technology for high-level-waste disposal employing a multibarrier concept using engineered and natural barrier in stable bedrock at 300-1,000 m depth is being commercialized as a safe, long-term isolation method for high-level waste, including spent nuclear fuel. Managing heat generated from waste is important for improving disposal efficiency; thus, research on efficient heat management is required. In this study, thermal management methods to maximize disposal efficiency in terms of the disposal area required were developed. They efficiently use the land in an environment, such as Korea, where the land area is small and the amount of waste is large. The thermal effects of engineered barriers and natural barriers in a high-level waste disposal repository were analyzed. The research status of thermal management for the main bedrocks of the repository, such as crystalline, clay, salt, and other rocks, were reviewed. Based on a characteristics analysis of various heat management approaches, the spent nuclear fuel cooling time, buffer bentonite thermal conductivity, and disposal container size were chosen as efficient heat management methods applicable in Korea. For each method, thermal analyses of the disposal repository were performed. Based on the results, the disposal efficiency was evaluated preliminarily. Necessary future research is suggested.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.530-545
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• 2023

As an alternative to conventional management options for a lot of concrete waste from decommissioning of nuclear power plants, a set of scenarios for controlled recycling of decommissioning concrete waste as engineered barriers of a radioactive waste repository was proposed, and a comprehensive safety assessment model and framework covering both pre-and post-closure phases was newly developed. The new methodology was applied to a reference vault-type repository, and the ratios of derived concentration limits to unconditional clearance levels of eighteen radionuclides for controlled recycling were provided for three sets of dose criteria (0.01, 1, and 20 mSv/y for the pre-closure and 0.01 mSv/y for the post-closure phases). It turns out that decommissioning concrete waste whose concentration is much higher than the unconditional clearance level can be recycled even when the dose criterion 0.01 mSv/y is applied. Moreover, a case study on ABWR bio-shield shows that the fraction of recyclable concrete waste increases significantly by increasing the dose criterion for the radiation worker in the pre-closure phase or the duration of storage prior to recycling. The results of this study are expected to contribute to demonstrating the feasibility of controlled recycling of a lot of decommissioning concrete waste within nuclear sectors.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1047-1059
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• 2019

This work describes the development of a numerical module with a multiphysics structure to simulate the thermo-hydro-chemo-mechanical behavior of compacted bentonites. First, the conceptual model, based on the state-of-the-art formulation for clay-based engineered barriers in deep geological repositories, is described. Second, the advantages of multiphysics-based modules are highlighted. Then, the guidelines to develop a code using such tools are outlined, presenting an example of implementation. Finally, the simulation of three tests that illustrate the behavior of compacted bentonites assesses the scope of the developed code. The satisfactory results obtained, and the relative simplicity of implementation, show the opportunity of the modeling strategy proposed.

• 방사성폐기물학회지
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• 제3권4호
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• pp.329-333
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• 2005

모의지하수중에서 가압경수로형 사용후핵연료로부터 세슘의 침출률에 미치는 공학적 방벽 영향을 규명하기 위하여 지난 약 6년간 벤토나이트 또는 금속시편등의 존재여부에 따라 침출시험을 수행하였다. 침출률은 시간이 경과함에 따라 지수함수적으로 감소하는 경향을 나타내었으며, 적정시간이 경과한 다음부터는 일정한 값에 수렴하는 경향을 나타내었다. 벤토나이트 또는 금속시편이 있을 경우 세슘의 누적누출분률은 선형적으로 증가하였으나, 이들이 없는 경우의 누적분률은 급격히 증가한 다음 서서히 증가하는 경향을 보였다. 이 누적분률에서 갭에 존재하는 세슘의 재고량을 제한 값은 공학적 방벽이 존재하는 경우의 누적분률에 거의 근접하였다. 이러한 결과들은 사용후핵연료 중 세슘의 초기누출분률은 갭 중 세슘의 재고량에 의존하지만, 세슘의 장기침출률은 공학적 방벽에 거의 영향을 받지 않음을 암시해 주고 있다. 그러나 세슘의 초기침출률은 공학적 방벽의 지연효과로 감소될 수 있을 것이다. 그리고 처분장에서 사용후핵연료 중 세슘의 장기침출률은 $2\times10^{-2}\;g/m^2-day$를 넘지않는 범위 내에서 일정한 값을 가질 것이다.