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NRC Issues Draft Guidance for Flooding Hazard Integrated Assessments

The following news article originally appeared in NEI’s Nuclear Energy Overview.

The NRC has issued for public comment draft interim staff guidance for U.S. nuclear energy facility operators to evaluate their sites’ responses to reanalyzed flooding hazards that exceed levels the plants were designed to withstand.

The guidance outlines an acceptable method for reactor licensees to meet one of the requirements outlined in a March 12 request for information the agency issued as part of its response to the Fukushima accident.

The request called for licensees to use the latest available information and analysis methods to analyze site-specific flooding hazards, including stream and river flooding, hurricane storm surges, tsunamis, and dam failures.

If the re-evaluated flooding hazards exceed design-basis levels a plant was originally designed to withstand, the guidance requests the operator to perform an “integrated assessment” of the plant’s specific vulnerabilities and its response capabilities, including physical barriers, temporary protective measures and operational procedures.

The integrated assessment must consider all modes of plant operation that could be affected by a flood, including events that could reasonably be expected to occur concurrent with the flood. The guidance says a flooding event cannot be excluded from the analysis based “solely on how rare the flood might be.” The assessment report also should outline interim measures operators will use to deal with the re-evaluated hazard.

The guidance says the agency will review licensee responses to the request for information and determine whether further regulatory action is required to protect plants from flooding hazards. Licensees that must perform the integrated assessments are required to complete them two years after submittal of their flooding re-evaluations.

The guidance is not mandatory. The NRC said it will evaluate alternate approaches when submitted by licensees.

The draft guidance is available in the NRC’s ADAMS document control system under accession number ML12235A319. The NRC will accept comments until Oct. 29. NEI is collecting significant generic comments to submit to the agency on behalf of industry.

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