Jae-Wook Jung

As climate change increases typhoon intensity and frequency, typhoon-induced high winds increasingly threaten nuclear power plant (NPP) safety by disrupting off-site power systems. Previous probabilistic safety assessments (PSAs) evaluated this risk using transmission tower fragility models derived from high-wind fragility equations developed for NPP structures, systems, and components. However, these models do not adequately reflect the structural characteristics of Korean transmission towers. In this study, a PSA of the off-site power system at the Kori NPP site under typhoon-induced high winds was performed using a universal voltage-class-based fragility model developed for Korean transmission towers. To isolate the effect of the fragility model on risk estimates, the typhoon hazard, network, and damage correlation conditions were set identically to those adopted in previous research. The Korean universal fragility model produced a higher median wind speed but a lower high-confidence-of-low-probability-of-failure capacity, resulting in an increase in the estimated annual risk. Because the lower HCLPF extends the probability of damage to lower wind speeds, which occur more frequently, the annual risk increases despite the greater median capacity. The risk-contribution analysis showed that the overall risk was governed by the overlap between the 0–50% range of the fragility curve and the hazard below its 100-year return period, rather than by the median failure wind speed. The analysis further demonstrated that the choice of logarithmic standard deviation shifts the governing wind-speed range. Therefore, realistic assessments require fragility models developed specifically for Korean transmission towers. These findings provide a quantitative basis for estimating the frequency of loss of off-site power events at NPPs, thereby contributing to resilient and sustainable infrastructure management.

ISRS) 및 층응답스펙트럼(Floor Response Spectrum: FRS)은 원자력발전소(원전

The behavior of short‐period reinforced concrete (RC) shear wall structures is often complicated and hard to predict accurately, even when the structure behaves in the elastic region, due to significant uncertainties in the material and the environment. Modeling assumptions used in finite element (FE) analyses often influence the accuracy of the dynamic response predictions. This paper discusses the numerical modeling of shaking table tests of a 3‐story RC shear wall specimen, which was carried out by Korea Atomic Energy Research Institute in July 2020. The experimental program is briefly introduced in this paper. Through nonlinear time history analyses using ABAQUS, the effect of modeling assumptions on the accuracy of the FE methods in predicting the linear and moderately nonlinear behavior of the RC structure is presented. Two commonly used modeling/model updating assumptions are considered: concrete Young's modulus and foundation flexibility. Influences of such modeling assumptions in predicting beyond design dynamic behavior (i.e., nonlinear responses and damage development) of the testing structure are also studied. The results showed that the accuracy of the dynamic response prediction of the structure could be improved significantly after calibrating the models against the white noise test results. Nevertheless, models established with different modeling assumptions can only capture the behavior of the structure at certain seismic intensity levels. Different models give results with a considerable variation in the structure's peak acceleration, floor response spectrum, acceleration amplification profile, damage pattern, and damage severity.

Seismically isolated nuclear power plants (NPPs) can provide substantial benefits towards reducing the failure probability of NPPs, especially for beyond design basis earthquake shaking. One risk posed by seismic isolation is the potential for pounding to a stop or moat wall, with currently little guidance provided by design standards on how to address this concern. In this paper, a structural model of an isolated NPP based on the Advanced Power Reactor 1400 MW is enveloped with moat walls and advanced bearing models. The bearing models account for large strain behavior through failure based on full-scale experiments with lead rubber bearings (LRBs). Using these analytical models and a measured ultimate property diagram from LRB failure tests, the range of clearance to the stop considering the performance criteria for the NPP is investigated. Although the analysis results are dependent on the particular models, ground motions, and criteria employed, this research provides an overview of the seismic response and performance criteria of an isolated NPP considering the clearance to the stop.

When acquiring accurate ultrasonic images, we must precisely estimate the mechanical properties of the soft tissue. This study investigates and estimates the viscoelastic properties of the tissue by analyzing shear waves generated through an acoustic radiation force. The shear waves are sourced from a localized pushing force acting for a certain duration, and the generated waves travel horizontally. The wave velocities depend on the mechanical properties of the tissue such as the shear modulus and viscoelastic properties; therefore, we can inversely calculate the properties of the tissue through parametric studies.