The Nuclear Regulatory Commission (NRC), after reviewing updated earthquake hazard information from all U.S. nuclear power plants, has concluded the plants can, where appropriate, complete in-depth analyses of their updated earthquake risk earlier than originally planned.
In other cases, the NRC has concluded reactors no longer need to submit an in-depth analysis.
NRC made the announcement in an Oct. 28 news release. The emphasis on seismic risk to nuclear plant sites is part of NRC’s increased attention to low-probability, high-impact accidents following the 2011 Fukushima Dai-ichi nuclear disaster in Japan.
Several months after the massive (Magnitude 9) earthquake and tsunami that crippled the Tokyo Electric Power Fukushima reactors, a far smaller event happened in the United States.
A rare earthquake on the East Coast of the United States, with a Magnitude of 5.8, occurred in Virginia during August 2011. The epicenter was located within miles of the Dominion (NYSE:D) North Anna nuclear station in Louisa County. While the plant evidently suffered only cosmetic damage, it was shut down for several weeks for inspection. It was eventually determined that North Anna exceeded “design limit for ground acceleration,” according to NRC.
In the aftermath of Fukushima, all U.S. nuclear plants were asked to re-analyze their earthquake hazards. NRC has reviewed the submittals, beginning with Central and Eastern U.S. plants in 2014, and then the Western U.S. plants earlier this year.
The agency also considered insights from earlier probabilistic risk assessments related to seismic hazards. In addition, the agency reviewed the plants’ evaluations on whether any interim measures are called for while they complete an in-depth risk analysis.
The NRC said Oct. 27 that it continues to conclude U.S. reactors are safe to continue operating while they do more analysis where appropriate.
“Our substantial reviews have shown that fewer reactors than we first thought actually need the in-depth analysis,” said Bill Dean, director of the NRC’s Office of Nuclear Reactor Regulation. “This outcome means both the NRC and industry can better focus their seismic expertise to work on the plants most in need of additional analysis. We now expect the first in-depth risk analysis to be completed three months ahead of the original schedule, and the last ones potentially a year ahead of their original deadline.”
The NRC has concluded the plants have appropriately reviewed their existing seismic protection. It is also worth noting that many U.S. reactors already comply with the NRC’s March 2012 Orders for additional safety equipment and enhanced spent fuel pool monitoring.