It has long been recognised that external hazards can present a potential common cause source of initiating events that could challenge nuclear power plant safety. Modelling of these hazards is a common practice found in many countries. Consequently, the effective screening of external hazards provides an efficient modelling practice for risk assessment. However, current practice indicates a wide variety of criteria being used to screen external hazards for further consideration in NPP risk assessments. The objective of this activity is to provide the results of a survey of current approaches to external hazard screening and to describe potential science-based screening of external hazards. This report identifies both best practices and gaps that exist in the specification of such screening processes based on the current state of the practice.
The report contains a summary of external hazard screening practices from several countries including Canada, Germany, Finland, Russia, Switzerland and the United States, as well as international organisations such as the International Atomic Energy Agency, the Western Europe Nuclear Regulators Association, the Advanced Safety Assessment Methodologies: extended PSA (ASAMPSA) project and the Nuclear Energy Agency.