As climate change and population growth raise the likelihood of natural disasters, it becomes crucial to comprehend and mitigate these risks in vital infrastructure systems, especially nuclear power plants (NPPs). This research addresses the necessity for evaluating multiple hazards by concentrating on slope failures triggered by earthquakes near NPPs over a timeframe extending up to a return period of 100,000 years. Utilizing a Geographical Information System (GIS) and Monte Carlo Simulation (MCS), the research conducts a comprehensive fragility assessment to predict failure probability under varying ground-shaking conditions. According to the Newmark displacement method, factors such as Peak Ground Acceleration (PGA), slope angle, soil properties, and saturation ratio play significant roles in determining slope safety outcomes. The investigation aims to enhance understanding seismic event repercussions on NPP-adjacent landscapes, providing insights into long-term dynamics and associated risks. Results indicate an increase in slope vulnerability with longer return periods, with distinct instances of slope failures at specific return periods. This analysis not only highlights immediate seismic impacts but also underscores the escalating risk of slope displacement across the extended return period scales, crucial for evaluating long-term stability and associated hazards near nuclear infrastructure.

Due to the recent increase in domestic seismic activity and the proliferation of PC structure buildings, there is a pressing need for a fundamental study to develop and revise the design criteria for Half-PC slabs. In this study, we propose criteria for determining the rigid diaphragm based on the aspect ratio of Half-PC slabs and investigate the structural effects based on the presence of chord element installation. This study concluded that Half-PC slabs with an aspect ratio of 3.0 or lower can be designed as rigid diaphragms. When chord elements are installed, it is possible to design Half-PC slabs with an aspect ratio of 4.0 or lower as rigid diaphragms. In addition, the increase in the aspect ratio of the Half-PC slab leads to a decrease in the in-plane stiffness of the structure, confirming that the reduction effect of the maximum displacement in force direction (max ) due to the increase in wall stiffness is predominantly influenced by flexibility.

In the case of the Pohang earthquake, which had a magnitude of 5.4 in 2017, geotechnical damages such as liquefaction and ground settlement occurred. The need for countermeasures has emerged, and experimental research in the Pohang area has continued. This study collected undisturbed samples from damaged fine-grained soil areas where ground settlement occurred in Pohang. Cyclic tri-axial tests for identifying the dynamic characteristics of soils were performed on the undisturbed samples, and the results were analyzed to determine the cause of ground settlement. As a result of the study, it was determined that in the case of fine-grained soils, ground settlement occurred because the seismic load as an external force was relatively more significant than the shear resistance of the very soft fine-grained soils, rather than due to an increase in excess pore water pressure.

In light of recent significant seismic events in Korea and worldwide, there is an urgent need to reevaluate the adequacy of seismic assessments conducted during facility construction. This study reexamines the ongoing viability of the Safety Shutdown Earthquake (SSE) criteria assessment for the Combustible Radioactive Waste Treatment Facility (CRWTF) site at the Korea Atomic Energy Research Institute (KAERI), originally established in 1994. To validate the SSE assessment, we delineated 13 seismic structure zones within the Korean Peninsula and employed two distinct methodologies. Initially, we updated earthquake occurrence data from 1994 to the present year (2023) to assess changes in the site’s horizontal maximum earthquake acceleration (g). Subsequently, we conducted a comparative analysis using the same dataset, contrasting the outcomes derived from the existing distance attenuation equation with those from the most recent attenuation equations to evaluate the reliability of the applied attenuation model. The Safety Shutdown Earthquake (SSE) criterion of 0.2 g remains unexceeded, even when considering recent earthquake events since the original evaluation in 1994. Furthermore, when applying various assessment equations developed subsequently, the maximum value obtained from the previously utilized ‘Donvan and Bornstein’ attenuation equation is 0.1496 g, closely resembling the outcome derived from the recently employed ‘Lee’ reduction equation of 0.1451 g. The SSE criteria for CRWTF remain valid in the current context, even in light of recent seismic occurrences such as the 2016 Gyeongju earthquake. Additionally, the attenuation equation employed in the evaluation consistently yields conservative results when compared to methodologies used in recent assessments. Consequently, the existing SSE criteria remain valid at present. This study is expected to serve as a valuable reference for confirming the SSE criterion assessment of similarly constructed facilities within KAERI.

When an earthquake occurs, the severity of damage is determined by natural factors such as the magnitude of the earthquake, the epicenter distance, soil properties, and type of the structures in the affected area, as well as the socio-economic factors such as the population, disaster prevention measures, and economic power of the community. This study evaluated the direct economic loss due to building damage and the community’s recovery ability. Building damage was estimated using fragility functions due to the design earthquake by the seismic design code. The usage of the building was determined from the information in the building registrar. Direct economic loss was evaluated using the standard unit price and estimated building damage. The standard unit price was obtained from the Korean Real Estate Board. The community’s recovery capacity was calculated using nine indicators selected from regional statistical data. After appropriate normalization and factor analysis, the recovery ability score was calculated through relative evaluation with neighboring cities.

In this study, in order to establish a strategy for developing an fire following earthquake risk assessment method that can utilize domestic public databases(building datas, etc.), the method of calculating the ignition and fire-spread among the fire following earthquake risk assessment methodologies proposed by past researchers is investigated After investigating and analyzing the methodology used in the HAZUS-MH earthquake model in the United States and the fire following earthquake risk assessment methodology in Japan, based on this, a database such as a domestic building data utilized to an fire following earthquake risk assessment method suitable for domestic circumstances (planned) was suggested.

This study proposes a methodology for assessing seismic liquefaction hazard by implementing high-resolution three-dimensional (3D) ground models with high-density/high-precision site investigation data acquired in an area of interest, which would be linked to geotechnical numerical analysis tools. It is possible to estimate the vulnerability of earthquake-induced geotechnical phenomena (ground motion amplification, liquefaction, landslide, etc.) and their triggering complex disasters across an area for urban development with several stages of high-density datasets. In this study, the spatial-ground models for city development were built with a 3D high-precision grid of 5 m x 5 m x 1 m by applying geostatistic methods. Finally, after comparing each prediction error, the geotechnical model from the Gaussian sequential simulation is selected to assess earthquake-induced geotechnical hazards. In particular, with seven independent input earthquake motions, liquefaction analysis with finite element analyses and hazard mappings with LPI and LSN are performed reliably based on the spatial geotechnical models in the study area. Furthermore, various phenomena and parameters, including settlement in the city planning area, are assessed in terms of geotechnical vulnerability also based on the high-resolution spatial-ground modeling. This case study on the high-precision 3D ground model-based zonations in the area of interest verifies the usefulness in assessing spatially earthquake-induced hazards and geotechnical vulnerability and their decision-making support.

As a result of active geological investigation of faults in Korea, many Quaternary faults have been identified and some of them were judged to have potential to generate earthquakes. Those faults need to be considered as additional seismic sources in the seismic hazard analysis. When a fault is introduced as a new source, the earthquakes generated by the fault should be removed from the area sources that include any part of the fault, to avoid double counting. In practice, however, double counting cannot completely be avoided as the complete separation of the fault-generated earthquakes from the area sources is impossible due to uncertainties related to the earthquake location, subsurface structures of faults, etc. When a new fault source is introduced, the only constraint is the invariance of earthquake frequency. The maximum earthquake and the Richter-b value should also be subject to change, but there are no competent approaches to estimate the change due to incomplete separation of earthquakes. To gain insight into the effect of a new fault source, an example calculation of the seismic hazard were carried out. The example calculation shows that addition of a new fault source centers seismic hazard around the fault source.

It is essential to determine a proper earthquake time history as a seismic load in a seismic design for a critical structure. In the code, a seismic load should satisfy a design response spectrum and include the characteristic of a target fault. The characteristic of a fault can be represented by a definition of a type of possible earthquake time history shape that occurred in a target fault. In this paper, the pseudo-basis function is proposed to be used to construct a specific type of earthquake, including the characteristic of a target fault. The pseudo-basis function is derived from analyzing the earthquake time history of specific fault harmonic wavelet transform. To show the feasibility of this method, the proposed method was applied to the faults causing the Gyeong-Ju ML5.8 and Pohang ML5.3 earthquakes.

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

Based on the random-vibration-theory methodology, dynamic responses of nuclear facilities subjected to obliquely incidental and incoherent earthquake ground motions are calculated. The spectral power density functions of the 6-degree-of-freedom motions of a rigid foundation due to the incoherent ground motions are obtained with the local wave scattering and wave passage effects taken into consideration. The spectral power density function for the pseudo-acceleration of equipment installed on a structural floor is derived. The spectral acceleration of the equipment or the in-structure response spectrum is then estimated using the peak factors of random vibration. The approach is applied to nuclear power plant structures installed on half-spaces, and the reduction of high-frequency earthquake responses due to obliquely incident incoherent earthquake ground motions is examined. The influences of local wave scattering and wave passage effects are investigated for three half-spaces with different shear-wave velocities. When the shear-wave velocity is sufficiently large like hard rock, the local wave scattering significantly affects the reduction of the earthquake responses. In the cases of rock or soft rock, the earthquake responses of structures are further affected by the incident angles of seismic waves or the wave passage effects.

With the increase of temporarily-stored radioactive waste in Korea, the disposal of radioactive waste in a deep geological repository, which is located in crystalline rock at a depth of hundreds of meters below the ground level, has received great attention nowadays. To ensure the permanent isolation of radionuclides from the human and surrounding ecosystems, the safety assessment for the high-level radioactive waste disposal facilities is essential. For the reliable safety assessment of fractured rock, it is especially important to input proper hydraulic properties of fractures such as aperture and hydraulic conductivity, which can directly affect the fluid flow and radionuclide transport. Meanwhile, it has become important to consider sudden fault behavior caused by an earthquake with the recent occurrence of high-intensity earthquakes in the Korean Peninsula. The sudden fault behavior can induce the changes of the hydraulic properties of fractures. Since the changes of the hydraulic properties directly affects to the radionuclide transport in the fractured rock, it is important to estimate the effect of earthquake-induced stress change on hydraulic properties of fractures in the perspective of long-term safety assessment. In this study, the effect of an earthquake on the hydraulic properties of fractures was explored by a numerical approach. The static Coulomb stress change after the earthquake was calculated using software ‘Coulomb 3’ developed by United States Geological Survey (USGS) with the assumption for several mechanical properties such as Young’s modulus, Poisson’s ratio and effective coefficient of friction. The final stress after earthquake occurrence was calculated as the sum of the initial stress and the stress change. Thereafter, the normalized transmissivity of fracture after the earthquake was calculated using the final stress from the stress-transmissivity relationship. Using the methodology for calculating fracture transmissivity change induced by the earthquake developed in this study, the effect of several factors, such as the earthquake magnitude and the distance between fracture and epicenter, was additionally explored. The newly developed methodology will be applied to the processbased total system performance assessment framework (APro) being developed by KAERI, and this study is expected to be helpful for the safety assessment considering long-term evolution phenomena including earthquakes.

In assessing the seismic safety of nuclear power plants, it is essential to analyze the structures using the observed ground motion. In particular, spatial variation in which the characteristics of the ground motion record differ may occur if the location is different within the site and even if the same earthquake is experienced. This study analyzed the spatial variation characteristics of the ground motion observed at the structure and site using the earthquake records measured at the Hamaoka nuclear power plant. Even if they were located on the same floor within the same unit, there was a difference in response depending on the location. In addition, amplification was observed in Unit 5 compared to other units, which was due to the rock layer having a slower shear wave velocity than the surrounding bedrock. Significant differences were also found in the records of the structure’s foundation and the free-field surface. Based on these results, the necessity of considering spatial variation in the observed records was suggested.

국내 지진 발생의 빈도는 점차 증가하는 추세에 있으며, 포항지진(5.4 규모)은 진앙지와 주민 거주지가 가까워 피해 가 심각했는데 건물의 외장재가 떨어져 차량 등에 2차 피해가 발생하여 건물 외장재 안전에 대한 우려가 커지고 있는 실정이 다. 따라서 본 연구에서는 비구조 요소 중 커튼월의 동적 내진성능평가 규격에 대한 세계 각 국의 규준을 고찰하고 이 중에서 가장 널리 통용되는 AAMA501. 6-18에 따라 그 동적 내진성능을 평가하고자 한다. 또한, 본 연구에서 수행한 3축 동적 지진파 대응 가능 커튼월 시스템 실험을 통해 지진에 대한 2차 피해 방지를 위한 내진 커튼월 설계시공지침 개발에 기초적 자료로 제 공하고자 한다.

연구에서는 한국 시민들의 지진 재해 준비도를 알아보기 위해 지진에 대한 지식, 인지, 대처의 3개 구인으로 구성된 설문 문항을 개발하고 비례 층화 표본 추출 방법으로 수집된 1,256명 시민의 응답을 라쉬분석, 추리통계, 군집 분석 기법을 이용하여 분석하였다. 연구 결과는 다음과 같다: 첫째, 시민들의 지진 재해 준비도 분석 결과, 전체적으로 시민들의 지진 재해 준비도는 ‘보통’ 수준이었으며, 지식과 인지에 비해 대처가 상대적으로 낮은 것으로 나타났다. 둘째, 지진 재해 준비도와 관련된 변인 분석 결과, 지진 재해 준비도에 영향을 주는 변인으로는 성별, 교육 수준, 실제 거리, 안전 인식이 있었다. 셋째, 지진 재해 준비도의 3개 구인 간 상관관계를 분석한 결과, 지식, 인지, 대처 세 가지 구인은 높은 상관을 나타내 구조적으로 서로 밀접한 관계를 보였다. 또한, 성별과 교육 수준이 달라도 이러한 구조적 상관은 비슷하게 나타났다. 군집 분석 결과, 5개 유형의 집단으로 구분되었으며 지진 재해 준비도 3개 구인의 수준이 중간 정 도로 서로 비슷한 집단 유형이 대부분을 차지하였다. 이 연구 결과를 토대로 시민들의 지진 재해 준비도 함양을 위한 교육의 지향점을 제안하였다.

최근 들어 한반도에 중규모의 지진이 연속해서 발생함에 따라 중앙정부와 지방자치단체에서는 지진방재 대책을 새로이 마련하고 있다. 지진재해 분석에서 가장 핵심적인 정보는 지질과 지반정보로 여러 관계기관에서 관련자료를 수 집하고 DB를 구축하고 있다. 하지만, 실제 이러한 정보들을 지자체의 지진방재 대책 수립에 이용하고자 할 때는 여러 문제점이 발생하고 있다. 지질정보의 경우, 소축척 지질도는 개략적으로 표현이 되어 세부적인 특징을 보여주기가 어렵 고, 대축척 지질도는 도폭 간의 경계에서 암상이 불일치하거나 구조선의 연장이 불분명하다. 지반정보의 경우, 디지털화 가 이루어지지 않고 사장된 정보들이 다수 존재한다. 이러한 문제를 해결하기 위해 지진방재 대책의 기초단위인 지방자 치단체 단계에서의 지질·지반정보관리 정책방안을 제시하였다. 첫째, 이미 생산되었거나 생산될 지질정보와 지반정보를 보다 효율적이고 전문적으로 이용하기 위하여 산학연 기술연계 방안이 필요하다. 둘째, 많은 지질과 지반정보가 축적될 수 있도록 자치법규 제정 및 개정이 요구된다. 셋째, 지질·지반정보의 질적 향상을 위하여 전문가시스템 도입방안이 마 련되어야 한다. 넷째, 효율적인 정보의 관리를 위하여 전담부서 신설과 예산지원 확대가 필요하다.

지진은 지각내 단층운동과 함께 수십억 년 전부터 발생하여 왔다. 1960년대부터는 미국에서는 지진과 지하수위 의 연관성 연구를 본격적으로 시작하였으나, 국내에서는 2010년 경부터 지진과 지하수위 및 수리지화학적 연관성에 대 한 연구를 시작하였다. 본 연구에서는 국내학자들이 과거부터 2021년까지 연도별로 지진과 지하수의 관련성을 연구한 논문을 Web of Science에서 검색하고, 분야별(지하수위, 수리지화학, 지하수위와 수리지화학 병행, 그 외 분야) 연구 특 성을 검토하였다. 국내학술지에 게재된 지진과 지하수 관련성 연구 논문을 보면, 연도별 논문 편수는 2011년에 동일본 대지진, 2016년에 경주지진, 2017년에 포항지진과 발생과 관련되며, 이에 따라 2011년, 2018년, 2019년, 2020년에 국내 및 국제학술지 게재 논문수가 증가하였다. 대부분의 지하수위와 지진의 관련성 연구는 지진과 동시기의 지하수위 변화 에 관한 연구이며, 지진 전조와 관련한 연구는 거의 없다. 지하수위 관측자료와 함께 여러가지 수리지화학적 정보와 미 생물은 지진에 의한 기반암내 지하수의 유동과 화학적인 반응을 보다 상세하게 이해하는데 도움을 줄 수 있다. 지진 감시 및 예측을 위해서는 지진감시를 위한 지하수관측공 네트워크를 전국적으로 구축할 필요가 있다.