• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2821-2835
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• 2020

The phenomenon identification and ranking table (PIRT) is an important basis in the nuclear power plant (NPP) thermal-hydraulic analysis. This study focuses on the importance ranking of the input parameters when lacking the PIRT, and the target scenario is the small break loss of coolant accident (SBLOCA) in a pressurized water reactor (PWR) CPR1000. A total of 54 input parameters which might have influence on the figure of merit (FOM) were identified, and the sensitivity measure of each input on the FOM was calculated through an optimized moment-independent global sensitivity analysis method. The importance ranking orders of the parameters were transformed into the Savage scores, and the parameters were categorized based on the Savage scores. A parameter importance ranking table for the SBLOCA scenario of the CPR1000 reactor was obtained, and the influences of some important parameters at different break sizes and different accident stages were analyzed.

• 방사성폐기물학회지
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• 제21권1호
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• pp.23-41
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• 2023

Coupled thermo-hydraulic-mechanical (THM) processes are essential for the long-term performance of deep geological disposal of high-level radioactive waste. In this study, a numerical sensitivity analysis was performed to analyze the effect of rock properties on THM responses after the execution of the heater test at the Kamaishi mine in Japan. The TOUGH-FLAC simulator was applied for the numerical simulation assuming a continuum model for coupled THM analysis. The rock properties included in the sensitivity study were the Young's modulus, permeability, thermal conductivity, and thermal expansion coefficients of crystalline rock, rock salt, and clay. The responses, i.e., temperature, water content, displacement, and stress, were measured at monitoring points in the buffer and near-field rock mass during the simulations. The thermal conductivity had an overarching impact on THM responses. The influence of Young's modulus was evident in the mechanical behavior, whereas that of permeability was noticed through the change in the temperature and water content. The difference in the THM responses of the three rock type models implies the importance of the appropriate characterization of rock mass properties with regard to the performance assessment of the deep geological disposal of high-level radioactive waste.

• Advances in aircraft and spacecraft science
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• 제10권1호
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• pp.83-106
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• 2023

In this work, the static behavior of FGM macro and nano-plates under thermomechanical loading. Equilibrium equations are determined by using virtual work principle and local and non-local theory. The novelty of the current model is using a new displacement field with four variables and a warping function considering the effect of shear. Through this analysis, the considered sandwich FGM macro and nanoplates are a homogeneous core and P-FGM faces, homogeneous faces and an E-FGM core and finally P-FGM faces and an E-FGM core. The analytical solution is obtained by using Navier method. The model is verified with previous published works by other models and very close results are obtained within maximum 1% deviation. The numerical results are performed to present the influence of the various parameters such as, geometric ratios, material index as well as the scale parameters are investigated. The present model can be applicable for sandwich FG plates used in nuclear, aero-space, marine, civil and mechanical applications.

• 한국지반공학회논문집
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• 제24권2호
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• pp.37-44
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• 2008

절취사면의 붕괴는 지질 및 지형적인 요건과 수리적인 요건 등 매우 다양한 요인들이 복합적으로 작용하여 발생한다. 그러나 현행 절취사면의 사전 및 사후 유지관리 단계에서 복잡한 지질조건에 따른 안정성 저해에 미치는 영향을 평가함에 있어 매우 미흡한 실정이다. 본 연구에서는 국내 유지관리 주체별 현황 및 암종별 붕괴 특성 및 유지관리 사례분석 등을 실시하고 이를 통하여 암종별 특성이 고려된 국내 절취사면의 유지관리 방안을 제시하고자 한다.

• Ocean Systems Engineering
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• 제12권3호
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• pp.335-358
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• 2022

Hydrodynamic field alteration around a cylindrical pier using a curved vane is numerically investigated. The curved vane with various angles ranged from 10 to 220 degree is placed at the upstream of the cylindrical pier. Laminar flow is adopted in order to perform the steady-state analysis. It is found that the flow separation leads to the formation of four bubbles depending on the value of the curved vane angle. Two bubbles are located in the region between the rear of the curved vane and the leading surface of the cylindrical pier, while the remaining two bubbles are located at the wake zone behind the cylindrical pier. Numerical analysis is performed to reveal the hydrodynamic field and influence of curved vane on the formation and evolution of the bubbles. It is found that the center and size of the bubble depend mainly on the value of the curved vane angle. It is observed that the flow velocity vector shows clearly the alteration in the flow velocity direction especially at the leading surface and rear surface of the curved vane owing to the occurrence of flow separation and flow dissipation along the circumference of the vane.

• Geomechanics and Engineering
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• 제31권2호
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• pp.223-235
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• 2022

Bearing capacity of shallow foundations is often determined for either dry or saturated soils. In some occasions, foundations may be subjected to external loading which is inclined and/or eccentric. In this study, the ultimate bearing capacity of shallow foundations resting on partially saturated coarse-grained cohesionless and fine-grained cohesive soils subjected to a wide range of combined vertical (V) - horizontal (H) - moment (M) loadings is rigorously evaluated using the well-established limit equilibrium method. The unified effective stress approach as well as the suction stress concept is effectively adopted so as to simulate the behaviour of the underlying unsaturated soil medium. In order to obtain the bearing capacity, four equilibrium equations are solved by adopting Coulomb failure mechanism and Bishop effective stress concept and also considering a linear variation of the induced matric suction beneath the foundation. The general failure loci of the shallow foundations resting on unsaturated soils at different hydraulic conditions are presented in V - H - M spaces. The results indicate that the matric suction has a marked influence on the bearing capacity of shallow foundations. In addition, the effect of induced suction on the ultimate bearing capacity of obliquely-loaded foundations is more pronounced than that of the eccentrically-loaded footings.

• 한국지하수토양환경학회지:지하수토양환경
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• 제29권4호
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• pp.21-31
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• 2024

Sumgol in Jeju Island plays a significant role in groundwater recharge due to its permeable hydrogeological characteristics. However, a quantitative assessment of the interrelationship between rainfall characteristics and rainwater inflows into Sumgols has not yet been conducted. Therefore, this study examined the characteristics of rainwater inflow into three Sumgols located in the eastern and western regions of Jeju Island and assessed hydrogeologic factors influencing these inflows. During two rainfall events, the studied locations in Sumgol exhibited different characteristics of rainwater inflows, despite experiencing similar rainfall events. Additionally, the delay time for rainwater to reach the Sumgol locations after the rainfall was influenced more by rainfall intensity than by cumulative amount of rainfall. In Sumgols located in non-volcanic ash soil with low hydraulic conductivity, such as those in agricultural areas, rainwater inflows were observed even with small rainfall and low rainfall intensity. This study suggests that rainfall intensity, soil characteristics, permeability of lava flows, and land use are key factors influencing rainwater inflow into Sumgols, revealing that soil characteristics and the permeability of lava flows have a greater impact on surface runoff than land use.

• Nuclear Engineering and Technology
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• 제56권8호
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• pp.3397-3404
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• 2024

The shield building of the AP1000 nuclear power plant serves as a crucial protective barrier against radioactive substances. However, past research indicates that structures are susceptible to experiencing aftershocks, which may lead to unforeseeable damage and potential radioactive material leakage. To address this issue, a finite element model of the shield building was established with the damage indexes of the tensile and compressive damage selected for further model analysis. According to the fundamental theory of reliability, the traditional incremental dynamic analysis method was used to analyze the seismic fragility of the shield building by inputting mainshock and aftershock sequences with three strength ratios. The results indicate that the seismic fragility of shield building may be underestimated without considering the influence of aftershocks and the damage state presents an upward tendency as the strength ratio increases. However, the cumulative damage caused by aftershocks is unlikely to exceed the initial damage induced by the corresponding mainshock. Overall, the aggravation of the compressive damage is less pronounced than the increase of the tensile damage as the strength ratio increases.

• 한국지하수토양환경학회지:지하수토양환경
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• 제12권4호
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• pp.1-7
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• 2007

본 연구에서는 모래층(sbt-1공), 실트질 모래층(sbt-2공) 및 모래와 실트질 모래의 혼합층(sbt-3공)에서 순간충격시험이 수행되었다. 그리고, 현장시험에 의해 산정된 수리전도도와 비저류계수를 이용하여 회수시험 시 지하수위 강하구역의 공극체적을 산정하였다. 순간충격시험의 해석은 KGS 모델이 가장 적합하였으며, 주입시험과 회수시험 시 평균수리전도도는 sbt-1공 $6.65{\times}10^{-5}$m/sec, sbt-2공 $6.33{\times}10^{-6}$m/sec, sbt-3공 $3.72{\times}10^{-5}$m/sec이며, 평균비저류계수는 sbt-1공 0.0225, sbt-2공 0.0177, sbt-3공 0.0259로 산정되었다. 투수량계수, 저류계수, 시험시간 및 시험공 제원을 이용하여 무차원 시간과 무차원 우물저류계수를 산정하였다. 그리고, Cooper 등(1967)이 제시한 변수 ${\alpha}$와 ${\beta}$를 이용하여 무차원 수두강하량이 선정되었다. 산정된 무차원 시간, 무차원 우물저류계수 및 무차원 수두강하량을 이용하여 순간충격시험 시의 영향반경이 산정되었다. 주입시험과 회수시험 시 평균영향반경은 sbt-1공 1.377 m, sbt-2공 1.253 m, sbt-3공 1.558 m로 산정되었다. 그리고, 회수시험 시 더미 회수에 의한 지하수위 강하구역의 공극체적은 sbt-1공 $145,636cm^3$, sbt-2공 $71,561cm^3$, sbt-3공 $100,418cm^3$로 산정되었으며, 시험공의 부피를 제외한 지하수위 강하구의 공극체적은 sbt-1공 $145,410cm^3$, sbt-2공 $71,353cm^3$, sbt-3공 $100,192cm^3$이었다.

• 한국토양비료학회지
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• 제22권3호
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• pp.163-172
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• 1989

본 연구는 구획경계선(區劃境界線)이 토양물리성(土壤物理性)의 공간변이(空間變異)에 미치는 영향을 알기 위하여 10년전 구획정리(區劃整理)로 논을 전전환(田轉換)한 맥류연구소(麥類硏究所)의 시험포지 화동(華東)미사질식양토(Fine clayey, mixed, mesic family of Aquic Hapludalfs)를 공시토양으로 하여 필지경계선(筆地境界線)을 횡단(橫斷)하여 토양물리성(土壤物理性)을 조사하고 조사성적을 고여(古與) 통계학적(統計學的) 방법(方法)과 지질(地質) 통계학적(統計學的) 방법(方法)으로 공간변이성을 해석하였다. 토양입경분포(土壤粒徑分布)는 10m 간격으로 $15{\times}15$ Grid의 교차 225 지점에서 채취한 토양시료를 이용하였고 포장용수량(圃場容水量), 전용적밀도(全容積密度), 포화수리전도도(飽和水理傳導度)등에 대한 물리성은 조사대상면적의 일부분에 대하여 2.5m 간격으로 $18{\times}33$ Grid의 교차지점중 594지점에서 포장조사법으로 직접 측정하였다. 시험 분석결과를 요약하면 다음과 같다. 1. 토양물리성(土壤物理性)의 변이계수(變異係數)는 4.8%에서 128.8%범위였다. 변이계수(變異係數)는 크기로 보아 포화수리전도도(飽和水理傳導度)는 고변이군(高變異群)으로 분류되었고, 전용적밀도(全容積密度)는 저변이군(低變異群) 그리고 기타 다른 물리성은 중변이군(中變異群)으로 분류할 수 있다. 2. 측정된 값의 평균치로부터 신뢰수준 95%에서 허용오차 10%이내의 정확성을 나타낼 수 있는 시료수는 포장용수량(圃場容水量)이 1개로 가장 적었고 포화수리전도도(飽和水理傳導度)는 687개로 가장 많은 시료수가 요구되었다. 기타 다른 물리성(物理性)은 6-69개의 범위를 나타내었다. 3. 도수분포곡선(度數分布曲線)과 Fractile diagram의 분석 결과 포화수리전도도(飽和水理傳導度)는 대수변환시(對數變換時) 정규분포성(正規分布性)을, 기타 다른 물리성은 실측치(實測値)가 정규분포성을 보였다. 도수분포곡선(度數分布曲線)상에서 평균치(平均値), 중앙치(中央値) 및 최빈치(最頻値)가 차이를 나타내는 특성의 산술평균(算術平均)은 곡선상의 평균에 비해 오차를 유발할 가능성이 컸다. 4. 계열상관(系列相關) 분석(分析)에 의하면 토양물리성(土壤物理性)은 모두 유의성 있는 종속성(從屬性)이 인정되었다. 자기상관(自己相關) 분석(分析) 결과(結果)는 남북방향으로 정상성(定常性)을 가지며 7.5~40m의 영향권(影響圈)을 보였고 토양 깊이간에도 차이가 있었다. 특히 토양의 깊이 50~60cm에서 대부분의 물리성이 비정상성(非定常性)을 보였다. 동서방향으로는 30㎝의 주기성(週期性)을 보이는 것이 특징적이며 구획폭(區劃幅)과 일치하여 구획에 따른 영농관리가 토양의 공간변이성(空間變異性)을 유발하는 원인들중 하나로 생각되었다.