Abstract
Abnormal weather conditions due to climate change are currently increasing on both global and local scales. It is therefore important to ensure the safety of the areas where major national facilities are located by analyzing risk quantitatively and re-evaluating the existing major facilities, such as nuclear power plants, considering the load and capacity of extreme flood conditions. In this study, a risk analysis method is developed that combines flood hazard curves with fragility curves using hydraulic and hydrological models by GIS tools and the @RISK model for the probabilistic flood analysis of nuclear power plant sites. A two-dimensional (2D) analysis is first carried out to estimate flood depths in various watershed scenarios, and a representative hazard curve for both external and internal flooding is made by applying a verified probability distribution type for the flood watersheds. For the analysis of flooding within buildings, an internal grid is constructed using GIS with related design drawings, and based on the flood depth results of the 2D analysis, a hazard curve for the representative internal inundation using a verified probability distribution type is presented. In the present study, walkdowns with nuclear experts are conducted around the nuclear power plant area to evaluate the fragile structures and facilities under possible flooding. After reviewing the 2D inundation analysis results based on the selected major equipment and facilities, the zones requiring risk assessment are re-assigned. A fragility curve applying probability distribution for the site’s major equipment and facilities is also presented. Failure risk analysis of the major facilities is then conducted by combining the proposed hazard and fragility curves. Results in the form of quantitative values are obtained, and the indicators for risks as well as the reliability and optimal measures to support decision-making are also presented. Through this study, it is confirmed that risk assessment based on the proposed probabilistic flood analysis technique is possible for flood events occurring at nuclear power plant sites.
Highlights
In recent years, the intensity of precipitation and the frequency of typhoons have increased due to an abnormal climate [1]
A fragility assessment is carried out on the major facilities at the nuclear power plant (NPP) site, after which a flood hazard curve and a facility fragility curve are combined to present the probability of flooding failure of the major facilities considering uncertainty
A probabilistic flood hazard curve is estimated by applying probability distribution to the values that result when an event occurs
Summary
The intensity of precipitation and the frequency of typhoons have increased due to an abnormal climate [1]. The purpose of the current study is to apply the probabilistic concept to the assessment of external and internal flood risk of a nuclear power plant (NPP) site for extreme rainfall events. To this end, a fragility assessment is carried out on the major facilities at the NPP site, after which a flood hazard curve and a facility fragility curve are combined to present the probability of flooding failure of the major facilities considering uncertainty. On the basis of this approach, it is believed that further research on ways to minimize flood risk in the future will be possible
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