U.S. nuclear plants face the first post-Fukushima test of their ability to withstand multiple natural disasters as Hurricane Irene bears down on an area shaken by a 5.8-magnitude earthquake.
The temblor yesterday knocked out power to Dominion Resources Inc.’s North Anna nuclear plant in Virginia and prompted 12 stations from North Carolina to Michigan to declare “unusual events,” the lowest-level emergency designated by the U.S. Nuclear Regulatory Commission.
Off-site power was later restored to North Anna, eliminating the need for back-up generators for cooling, the company said late yesterday. The plant’s twin reactors halted automatically during the quake, whose epicenter was less than 15 miles (24 kilometers) from the plant, about 85 miles southwest of Washington, according to the U.S. Geological Survey.
One of the plant’s four diesel generators, which powered the reactors’ cooling systems during the blackout, stopped working as a result of a coolant leak, Roger Hannah, a spokesman for the Nuclear Regulatory Commission, said in an interview. Dominion Resources called a fifth standby generator into service to replace the broken unit, Ryan Frazier, a spokesman for the Richmond, Virginia-based company, said in an e-mail.
Hurricane Irene Expected
As East Coast nuclear operators recover from the earthquake, they’re reviewing emergency plans in advance of Hurricane Irene’s expected arrival later this week. The storm’s current track set by the National Hurricane Center estimates Irene will go ashore in North Carolina on Aug. 27 before moving up the East Coast, possibly threatening New York and New England.
The double threat from the earthquake and hurricane is providing a test of the U.S. nuclear industry’s disaster preparation at a time when regulators and industry operators are studying the lessons of the disaster at Japan’s Fukushima Dai- Ichi plant.
The Fukushima reactors lost power after a magnitude 9 earthquake struck in March. The tsunami that followed the quake swamped the plant’s diesel generators, leading to a meltdown and the worst nuclear accident since Chernobyl.
“Based on all information we have thus far, the systems at every U.S. nuclear energy facility where the earthquake’s effects were felt responded as designed,” Tony Pietrangelo, senior vice president and chief nuclear officer at the Nuclear Energy Institute, a Washington-based industry group, said in a statement yesterday.
Workers at North Anna were trying to determine whether the generator was damaged during the earthquake or as the result of a mechanical failure, Hannah said.
North Anna, which generates 1,806 megawatts of power, enough to supply 450,000 homes, is designed to withstand a 6.2 magnitude earthquake, William Hall, another Dominion spokesman, said in an interview. Following yesterday’s temblor, the station declared an “alert,” the second-lowest of four emergency classifications set by the nuclear oversight agency.
Hall said a damage inspection was still under way at 6 p.m. New York time yesterday. He said he didn’t know when the plant would restart.
“We will be conservative,” he said.
12 ‘Unusual Events’
The earthquake was felt from Richmond to Toronto and as far west as Columbus, Ohio, and prompted power companies across the region to inspect pumps, motors and valves for damage. Twelve nuclear plants, including two as far west as Michigan, declared “unusual events,” the lowest of the four emergency designations set by the Nuclear Regulatory Commission, said Joey Ledford, a spokesman for the agency.
The quake shows why the industry shouldn’t wait to implement safety measures to guard against such events, said Bob Alvarez, a senior scholar at the Institute for Policy Studies, a group that pushes for tighter regulation on nuclear power.
“We don’t need to wait for earthquakes to fix safety weaknesses that have been lingering for several years,” Alvarez, 64, said.
After four Exelon Corp. nuclear plants in Pennsylvania and New Jersey declared unusual events, operators were performing “walk-downs” to scout for damage from the seismic activity, Chicago-based Exelon said in a statement.
PJM Interconnection LLC, which manages the electric grid for all or parts of 13 states and the District of Columbia, said about 2,700 megawatts of power generation was lost in Virginia and another 500 megawatts were lost in Pennsylvania and Ohio.
“There were outages, but they are local outages,” said Ray Dotter, spokesman for PJM, based in Valley Forge, Pennsylvania, in a telephone interview. “It wasn’t because the grid was unstable.”
U.S. nuclear plants are required to have batteries capable of powering a plant for four hours and diesel generators protected by a hardened structure. The power is necessary to keep nuclear fuel cool at the site, preventing a meltdown and a release of radiation.
The Nuclear Regulatory Commission inspected North Anna earlier this year to evaluate whether it’s prepared to withstand disasters and blackouts as part of a survey conducted in Fukushima’s aftermath at all 104 nuclear plants in the U.S.
In a May 13 letter to David Heacock, president and chief nuclear officer of Dominion subsidiary Virginia Electric & Power Co., the nuclear agency said its inspector hadn’t identified “any significant issues” with the station blackout diesel generator room and related equipment.
However, the agency noted that a study by North Anna of the plant’s fire and flood protection structures had identified vulnerable areas that were “not seismically designed.”
“The licensee will evaluate the issues above in order to determine if additional mitigation strategies are required,” the letter stated.
North Anna’s two reactors were licensed for commercial operation in 1978 and 1980. At that time, some of the systems weren’t required to be designed to seismic standards, Hall said.
“We will do everything that needs to be done,” he said.
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