Updated Dec. 5
An earthquake measuring 2.1 on the Richter scale struck 1 kilometer south-southwest of North Plymouth Tuesday evening, according to a bulletin from the U.S. Geological Survey.
The exact coordinates were 41.957 degrees north, 70.692 degrees west. The earthquake occurred at a depth of 8.9 kilometers, the bulletin states.
The earthquake was not felt at Pilgrim Nuclear Power Station, according to Holtec spokesman Patrick O’Brien, who said the plant and spent fuel pool weren’t affected.
But all around Pilgrim, social media was abuzz with reports of a loud bang and rumbling — some people attributing it to snowplows until the earthquake was confirmed by the U.S. Geological Survey and the Massachusetts Emergency Management Agency.
Several reports were in the Bartlett Road area and the Pine Hills development, both within three to five miles of the plant. Rumblings were also felt in Plymouth Center, according to the social media posts.
One person described it as a “thundering” sound, another saying it “rattled glasses on a rack.”
Longtime Pilgrim critic and litigant Mary Lampert of Duxbury told The Times that “the quake raises issues.”
Lampert emailed that the geologic event underscored that there was “no basis” for the emergency response exemption granted to Holtec for Pilgrim. Lampert asked if Holtec shared seismic readings it took at the plant with state agencies. “State public safety officials communicated with Pilgrim Nuclear Power Station after last night’s earthquake and confirmed that there were no issues at the station,” Massachusetts Emergency Management Agency spokesman Christopher Besse emailed. Asked if Holtec shared in-house seismic readings with his agency, Besse wrote, “[t]hey did not.” Lampert also questioned whether the crane used to hoist radioactive fuel assemblies from the spent fuel pool into storage casks was designed to handle earthquake activity.
“I would like to see the calculated seismic response of Pilgrim’s [Single Failure Proof] Crane swinging a loaded 40-ton cask,” she emailed. “Would the cask serve to stabilize the crane during repeated seismic waves; or would it be rock-a-bye baby in a [Boiling Water Reactor] tree-top?”
“U.S. nuclear power plants are built to withstand a broad spectrum of environmental hazards, including earthquakes,” Nuclear Regulatory Commission spokesman Neil Sheehan emailed The Times. “The NRC requires that safety-significant structures, systems and components be designed to take into account the most severe natural phenomena historically reported for the site and surrounding areas. The NRC then adds margin to predicted ground motions to provide for additional robustness and to account for any limitations on historical data. In other words, U.S. plants are designed to be safe based on historical environmental data, including the area’s predicted maximum credible earthquake.”
Sheehan went on to write the plant can detect seismic activity on its own.
“The NRC requires nuclear power plants to maintain operating seismic monitors on site. When an earthquake occurs, data recorded by the plant’s seismic instrumentation is used by the operators to make a rapid determination of the degree of severity of the event, including the need to shut down the plant when Operating Basis Earthquake (OBE) levels are exceeded. The data, coupled with plant walkdowns, or visual assessments, is used to make the initial determinations of whether the plant must be shut down, if it has not already been shut down by the plant operators or the perturbations resulting from the seismic event. Here is a link to an NRC Regulatory Guide on nuclear plant seismic instrumentation, including data recorders: https://www.nrc.gov/docs/ML0037/ML003739947.pdf .”
“In the case of Pilgrim, the plant no longer has an operating reactor,” Seehan continued. “As such, the primary focus of safety is on the spent fuel pool and dry cask storage facility. Both are designed with a high degree of robustness and capable of withstanding the levels of earthquake activity discussed above. The earthquake activity reported in Massachusetts on Tuesday would not have approached a level of concern for either the spent fuel pool or the dry casks at the plant. The NRC could dispatch an inspector to the site to independently verify the safety of the pool and dry casks if we had any safety concerns regarding either. Again, that is not the case with respect to this seismic activity.”
Updated to include comments from the Massachusetts Emergency Management Agency.