A review of COHRISK: Multihazard risk quantification software for nuclear power plants

A combination of more than one natural hazard can occur simultaneously by their inherent correlation or by coincidence. One well-known multihazard incident, the Tohoku earthquake-tsunami in Japan 2011, led to a core damage accident at the Fukushima Daiichi nuclear power plant (NPP) and caused significant damage to its community. But despite this accident raising significant awareness of multihazard safety in the nuclear safety engineering community, multihazard risk quantification methods and tools for NPPs are relatively less investigated when compared to those for single hazards. At the same time, some multihazard tools developed outside the nuclear engineering industry are inadequate for extension to NPPs because of the complex NPP systems and the response correlation between the systems, structures, and components. To resolve this problem, the authors have been conducting a series of projects on developing a method for multihazard risk quantification of NPP systems and have launched the related quantification software, Combined Hazard RISK (COHRISK). This paper presents a review of COHRISK including its conceptual background, methodology development, architecture, and future work.