Abstract
The purpose of this study is to investigate the soil-structure interaction (SSI) effect on the overall risk of a PWR containment building structure with respect to two failure modes: strength and displacement. The precise quantification of the risk within the seismic probabilistic risk assessment framework depends considerably on an accurate treatment of the seismic response analysis. The SSI effect is one of the critical factors to consider when accurately predicting structural responses in the event of an earthquake. Previous studies have been conducted by focusing more on the positive side of the SSI effects and the effects mainly on the seismic fragility result. Therefore, this paper presents the results of a study of the SSI effect on the overall risk. Also, the study relies on an emphasis on revealing a beneficial and a detrimental effect of the SSI by utilizing an example of the containment structure in three soil conditions and two main failure modes. As a result, the consideration of SSI shows a complete conflicting effect on the seismic fragility and risk results depending on two failure modes considered in this study. This has a positive effect regarding the strength failure mode, but this brings a negative effect regarding the displacement failure mode. The risk fluctuation width is particularly noticeable in the site having a considerable change in seismic hazard information such as Los Angeles on the western site of the US. Such results can be expected to be utilized in a future study for investigating the pros and cons of the SSI effect associated with various failure modes in diverse conditions.
Highlights
Strong earthquakes are not uncommon near the current sites of nuclear power plants
Such a situation once again sheds new light on the importance of seismic margin assessment (SMA) [4, 5] and seismic probabilistic risk assessment (SPRA) [6,7,8,9] practices after the individual plant examination of external events (IPEEE) for severe accidents [10]. e SMA is intended to estimate how much margin exists at a plant above a design basis earthquake event based on the seismic fragility information of major systems, structures, and components. e SPRA is a more complete framework than the SMA because it integrates the seismic fragility data and seismic hazard information
Taking into account the soil-structure interaction (SSI) effect has been considered as a beneficial factor in the seismic response [13]. e beneficial effect emerges with reductions in the internal force and drift in the structure as the soft soil in the entire soil-structure system causes an increased structural period owing to its flexibility and plays a significant role in amplifying the energy dissipation effect in the response
Summary
Strong earthquakes are not uncommon near the current sites of nuclear power plants. Is phenomenon has a negative impact on closely connected structures, for example, a nuclear power plant, by causing adjacent structures consisting of the nuclear power plant to crash into one another In this context, the USNRC has increased the soil-condition acceptance criterion which can neglect the SSI effect. In order to quantify the SSI effect from a total risk perspective, the seismic responses of a pressurized water reactor (PWR) containment building structure in three soil conditions, that is, fixed, hard, and soft, are analyzed, and these are utilized for the basic information in the SPRA. The beneficial and detrimental effects of the SSI on the risk outcomes are quantified, and the results are discussed
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