NRC Issues Draft Guidance for Seismic Risk Re-Evaluations

NRC Issues Draft Guidance for Seismic Risk Re-Evaluations

by vbarq

NRC staff has issued for public comment draft interim staff guidance for U.S. nuclear energy facility operators reassessing the ability of their plants to withstand earthquakes.
The guidance describes the NRC’s “acceptable method” for licensees to conduct enhanced “seismic margin assessments,” or SMAs, that would meet the requirements of a March 12 request for information the agency issued as part of its response to the Fukushima accident.

While the approach it outlines is not mandatory, the NRC said it would evaluate alternate approaches when submitted by licensees.
The NRC is requiring all operating U.S. nuclear plants to re-analyze potential earthquake risk using a two-phase process. In the hazard reassessment phase, facility operators will update characterizations of the types of seismic activity to be expected at each site, using seismic source models, seismic ground motion models and geologic data. The analyses will update potential ground motions across a range, or spectrum, of vibration frequencies, and the plants will compare the new spectra to their existing design basis.http://safetyfirst.nei.org/safety-and-security/nrc-issues-draft-guidance-for-seismic-risk-re-evaluations/