The risk that an earthquake would cause a severe accident at a U.S. nuclear plant is greater than previously thought, 24 times as high in one case, according to an Associated Press analysis of preliminary government data. The nation's nuclear regulator believes a quarter of America's reactors may need modifications to make them safer.
The threat came into sharp focus last week, when shaking from the largest earthquake to hit Virginia in 117 years appeared to exceed what the North Anna nuclear power plant northwest of Richmond was built to sustain.
The two North Anna reactors are among 27 in the eastern and central United States that a preliminary Nuclear Regulatory Commission review has said may need upgrades because those plants are more likely to get hit with an earthquake larger than the one their design was based on.
Just how many nuclear power plants are more vulnerable won't be determined until all operators recalculate their seismic risk based on new assessments by geologists, something the agency plans to request later this year. The NRC on Thursday issued a draft of that request for public comment.
The NRC and the industry say reactors are safe as they are, for now. But e-mails in an 11,000-page records request by AP show that NRC experts were worried privately this year that plants needed stronger safeguards.