The ANS Standards Committee has just published ANSI/ANS-2.8-2019, “Probabilistic Evaluation of External Flood Hazards for Nuclear Facilities.” The new standard supersedes ANS-2.8-1992, which was withdrawn in 2002.
What it covers: Approved December 17, 2019, the standard establishes a process for identifying and evaluating design-basis flood hazards at nuclear facilities using a probabilistic approach. This represents a major revision of the previous standard, which presented design-basis flood methodologies for evaluating probable maximum flood hazards but established those hazards using deterministic rules rather than probabilistic concepts.
A necessary rewrite: A working group formed in 2012 determined that a major rewrite of the 1992 standard was needed. Additionally, insights gained from flooding at the Blayais reactor in France in 1999, as well as experience with Hurricane Katrina in 2005 and, more recently, the 2011 tsunami in Japan, made it clear to the working group that a more formal probabilistic approach should be used for setting design flood parameters. The rewrite was focused on a probabilistic approach for assessing the magnitude and occurrence of flood hazards that could be used in applications for the evaluation of nuclear facilities, including risk assessments and the establishment of the design-basis flood hazard.