NRC Approves Industry Guidance for Seismic Hazard Re-Evaluations

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

The U.S. Nuclear Regulatory Commission has endorsed industry guidance for developing updated seismic hazard evaluations for nuclear energy facility sites. The guidance gives licensees the tools to prepare responses to the NRC’s detailed request for information, which was issued in March.

“The NRC staff has reviewed the NEI guidance document and concludes that responses … prepared using this guidance will be responsive to that request,” said David Skeen, director of the NRC’s Japan Lessons-Learned Project Directorate.

As part of its response to the 2011 reactor accident in Japan, the NRC in March asked all power reactor licensees and construction permit holders under 10 CFR Part 50 to re-evaluate the seismic hazard at their sites.

The process has two steps. First, licensees will re-evaluate the seismic hazards for their sites, using the industry-developed guidance. The updated calculations will be developed by combining seismic source models, seismic ground motion models, and details related to local site geology, Skeen said.

Facilities in the central and eastern United States will use a new seismic source model released in January 2012 to replace models in use since the late 1980s. The new model was the result of a four-year effort that involved the Electric Power Research Institute, the Department of Energy and the NRC.

Skeen said the NRC expects nuclear energy facilities in the central and eastern United States to meet the 18-month deadline in the NRC’s information request letter. Reactors in the west are in a different seismic region that was outside the scope of the study. Operators of those facilities will have to develop site-specific seismic source characterization models, EPRI said.

The second step of the process involves sites where the revised seismic hazard calculation exceeds the facility’s design basis. Companies that operate those facilities may need to perform additional studies to further characterize the seismic risk for their sites. The NRC estimates that about one-third of the sites will have to perform the risk analyses, while the industry believes that more than half the sites may have to do so.