Volcanic events are, at best, a parenthesis in current regulations or guidance for determining site suitability and for licensing decisions for most nuclear installations. This condition is understandable, as volcanic eruptions are rare natural events that have not created a significantly adverse condition at an operating nuclear installation. Nevertheless, unlike most geologic hazards, generally acceptable methodologies have not been established to assess volcanic hazards at a surface site or to determine if future volcanic events could be withstood by an appropriately designed nuclear installation. To address some of these challenges, the International Atomic Energy Agency (IAEA) has commissioned a multinational panel of consultants to revise preliminary guidance for assessing volcanic hazards at surface sites for nuclear installations. This chapter represents a summary of the consultants’ recommendations, which are being considered for adoption within an IAEA Safety Guide for volcanic hazards assessment.

The goal of this chapter is to formulate a systematic approach for evaluating volcanic hazards at any candidate surface site. The approach must be flexible enough to assess a broad range of complex, often interrelated volcanic phenomena, yet still provide a transparent methodology to support decision making. Two fundamental outcomes need to be supported by the volcanic hazards assessment. If the assessment determines that volcanic hazards are credible external events at a site, the results of the assessment will need to provide sufficient technical detail to support development of design bases or operational criteria to mitigate the effects of potential future events on safety (e.g. IAEA, 2003a).