The main mission of the Working Group on External Events (WGEV) is to improve the understanding and treatment of external hazards that would support the continued safety performance of nuclear installations, and improve the effectiveness of regulatory practices in NEA member countries.
The Working Group reports to the Committee on the Safety of Nuclear Installations (CSNI) and assists that Committee with its work. The Working Group also collaborates with, and responds to requests from, the Committee for Nuclear Regulatory Activities (CNRA) and other Working Groups of the CSNI. The WGEV programme of work is approved by CSNI.
The focus for the Working Group’s activities is external hazards that are of sufficient common interest to allow sharing of approaches for analysis and oversight. Determination of the response of structures and components to seismic hazards is performed by the Subgroup on Seismic Engineering of the Working Group on Integrity and Ageing of Components and Structures (WGIAGE), and combinations of seismic hazards with other hazards (e.g. flooding) are part of the WGEV scope. The Working Group on Risk Assessment (WGRISK) also performs work related to the assessment of the plant response and consequences of events including external hazards. Initially, these activities will concentrate on natural hazards. Man-made hazards will be addressed only if there is a particular link to a natural hazard, e.g. when a man-made hazard is used as a bounding or covering event for a natural hazard (for instance: protection against high winds is thought to be ensured by design against explosion pressure waves). Later on, the scope of work may be extended to include man-made hazards if a need for specific activities in this direction is identified. For external hazards, experience, lessons learnt and regulatory approaches are shared, and research activities and initiatives are identified to address knowledge gaps that lead to major uncertainties.
The Working Group is led by a chair, supported by a bureau of up to six of the leading members of the Working Group. Specifically, the WGEV:
The main mission of the Working Group on Integrity and Ageing of Components and Structures (WGIAGE) is to advance the current understanding of the relevant aspects related with ensuring the integrity of components, systems and structures (SSC), and to propose general principles on the optimal ways of dealing with respective challenges facing operating and new nuclear power plants as well as other nuclear facilities, and to make use of an integrated approach to design safety and plant life management.
The Working Group supports improved uses of Probabilistic Safety Assessment (PSA) in risk-informed regulation and safety management through the analysis of results and the development of perspectives regarding potentially important risk contributors and associated risk-reduction strategies. The Working Group addresses PSA methods, tools, and data needed to provide this information.