U.S. nuclear plants are at far greater risk from earthquakes than previously thought, with one-quarter of reactors in likely need of safety modifications, according to an Associated Press analysis of preliminary government data.
The quake threat to the nation’s aging nuclear plants has taken center stage since a 5.8-magnitude earthquake struck the East Coast on Aug. 23, causing rumbling from the Carolinas to Canada.
The epicenter of that quake was just 12 miles from Dominion Virginia Power’s North Anna Nuclear Plant, near Richmond. Two reactors at the plant automatically shut down and cooled during the quake, and “Unusual Events” were reported at 12 other plants nationwide, triggering stepped-up monitoring.
North Anna Concerns Continue
Although all other plants resumed normal operations within 48 hours, monitoring has continued at North Anna, where the plant automatically switched to diesel generators when the quake knocked out the regular power. The quake also shifted about two dozen spent fuel containers, but all remained intact, Dominion Virginia Power told the Associated Press.
Dominion Virginia Power
|Two nuclear reactors at the North Anna Power Station have not been restarted since the East Coast quake of Aug. 23.|
The Nuclear Regulatory Commission has beefed up its inspection team at North Anna since the quake, saying it may have affected the facility more than initially reported.
Dominion has said that the plant—originally licensed in 1978 and granted a 35-year renewal in 2003—could withstand a quake of 5.9 to 6.1 magnitude.
Ground Movement Analyzed
On Wednesday (Sept. 7), the NRC reported that it would hold a meeting Thursday (Sept. 8) to update the situation at North Anna, where the reactors have not been restarted.
At the meeting, Dominion is expected to discuss its latest analysis of ground motion at the plant and to outline the next steps in determining whether the plant meets NRC requirements to restart.
“Ongoing analysis by both the NRC and Dominion indicates the earthquake may have subjected the plant to more ground movement than specified in the plants’ designs,” the NRC said Wednesday.
The meeting will be broadcast live online. A final report on North Anna’s safety is not expected until mid-October.
Seismic Risks Studied
The NRC has been concerned about seismic risks to its facilities for some time, the AP reports. Well before the Japanese quake and nuclear disaster in March, the agency launched its first review in years aimed at updating the seismic risks to the 104-reactor U.S. system.
That preliminary review showed that 27 nuclear reactors in the Eastern and Central U.S. may need safety upgrades, because they are more likely to get hit with an earthquake larger than the one for which they were designed, the AP said.
The NRC has just drafted a request for all operators in the system to recalculate their own seismic risk based on new assessments by geologists. That request will likely not go out until late this year.
The NRC and the industry say reactors are safe as they are, for now, with a risk of core damage occurring in one accident every 500 years.
But emails obtained by the Associated Press “show that NRC experts were worried privately this year that plants needed stronger safeguards to account for the higher risk assessments.”
The news service noted: “Federal scientists update seismic assessments every five to six years to revise building codes for some structures. But no similar system is in place for all but two of the nation’s 104 reactors -- even though improving earthquake science has revealed greater risks than previously realized.”
The only exception is California’s Diablo Canyon plant, AP said, “which has been required to review the risk of an earthquake routinely since 1985.”
Otherwise, “the NRC does not require plants to re-examine their seismic risks to renew operating licenses for 20 years.”
‘Not a Good Story’
The AP said it had reviewed thousands of pages of NRC internal emails after the Japanese earthquake, including some expressing concern about possibly outdated analyses of quake risk to the U.S. system.
One seismologist acknowledged that recent science showed stronger quakes could happen. “Frankly, it is not a good story for us,” she wrote to agency colleagues.
Brian Sheron, who heads the NRC’s Office of Nuclear Regulatory Research, wrote in a March 14 email that updated numbers showed the government “didn’t know everything about the seismicity” in the central and eastern U.S., according to the AP.
“And isn’t there a prediction that the West Coast is likely to get hit with some huge earthquake in the next 30 years or so?” Sheron wrote. “Yet we relicense their plants.”