Overview of seismic probabilistic safety assessment applied to a nuclear installation located in a low seismicity zone

Abstract

Deterministic and probabilistic safety analysis methodologies have been developed and updated based on operational experience, investigation of past incidents or accidents, and analysis of postulated initiating events in nuclear plants in order to maintain the protection of workers, the public and the environment. The evaluation of accident sequences and the total radiological risk resulting from off-site releases are general objectives addressed by these methodologies. There are hazards that continually challenge the safety of a nuclear facility or its nearby area. In particular, seismic events represent a major contributor to the risk of a nuclear accident. Different levels of ground motion induced by earthquakes may be experienced by structures, systems and components (SSCs) of an installation. In this context, a seismic hazard analysis, seismic demand analysis and seismic fragility analysis must be carried out in order to characterize the local seismic hazard and seismic demands on SSCs, allowing an adequate seismic classification of SSCs, even for installations located in sites with low seismicity. In this article, a general description of the Seismic Probabilistic Safety Assessment (Seismic PSA) methodology is presented, emphasizing the supporting studies. This methodology shall be applied to an experimental nuclear installation containing a PWR reactor designed for naval propulsion to be installed in a low seismicity zone in Brazil.