* NRC-quake at its peak was twice plant design specs
* Dominion says shaking only 10-20 pct above parameters
* Regulatory, company engineers go head-to-head on impact
* Inspections thus far show no damage to safety systems
* Dominion hopes for quick restart, but NRC draws reins
(Recasts, updates with information from hearing, changes
dateline, Previously WASHINGTON)
By Roberta Rampton
ROCKVILLE, Md., Sept 8 Last month's record
earthquake in the eastern United States may have shaken a
Virginia nuclear plant twice as hard as it was designed to
withstand, a spokesman for the U.S. nuclear safety regulator
said on Thursday.
But Dominion Resources (D.N) told the Nuclear Regulatory
Commission that the ground under the plant exceeded its "design
basis" only by about 10 to 20 percent, and it plans to prove in
the next month that its reactors are safe to restart.
The discrepancy is one of many items the NRC and company
must deal with, in the first instance in which an operating
U.S. nuclear power plant has experienced a quake beyond its
The NRC must sign off on Dominion's restart plans for the
North Anna plant, about 12 miles from the quake's epicenter --
and determine how it will make that decision.
"You have the unique opportunity of being at the cutting
edge -- and whenever I say that, usually I get a response like,
'It feels like a bleeding edge,'" said Jack Grobe, deputy
director of the NRC's Office of Nuclear Reactor Regulation, to
officials from Dominion.
"It's not entirely clear to us exactly what we need in this
submittal from you. A summary may not do it," Grobe said near
the end of an exhaustive three-hour engineering face-off
between a dozen top officials from each side.
FACTBOX-U.S. nuclear plant quake risk [ID:nN1E77T21G]
Quake-hit US plant expects to restart [ID:nN1E7810PC]
INTERVIEW-NRC's Jaczko on quake [ID:nN1E780230]
Quake does little to shake town's faith [ID:nN1E78301Z]
FACTBOX-Post-Fukushima review of US plants [nN1E76C176]
TAKE A LOOK-U.S. maps out nuclear reforms [ID:nNUKEUSA]
Neither the company nor the NRC have found signs of serious
damage to safety systems at the North Anna nuclear plant,
although inspections by both sides continue.
NRC experts from a variety of nuclear engineering
disciplines peppered Dominion counterparts with questions about
the impact to fuel in the core, the strength of welds in plant
steels, and the resilience of underground pipes.
Dominion officials said it appears the North Anna reactors
shut when the earthquake caused a problem inside the cores at
both units rather than from the loss of power into the plant
from the outside grid as was initially believed.
Operators are still working to understand the "root cause"
of the plant shutdown, officials said.
Dominion touted a report by Robert Kennedy, a seismic
expert consultant from California. The company said he saw no
reason why the plant could not be safety restarted.
At Thursday's hearing, the toughest questions were about
items that are difficult to see with the naked eye, said Eugene
Grecheck, a Dominion vice president.
"You look at the things you know are most susceptible," he
told reporters. "If the paint hasn't chipped or cracked, then
you know there hasn't been any effect on the steel."
Grecheck would not directly comment on the NRC's comments
about the strength of the quake. He stressed that the strongest
vibrations lasted only a few seconds.
Dominion's analysis will be considered as the NRC does its
own analysis of what it will require the company to do to
restart operations, NRC spokesman Scott Burnell said.
The company said one reactor would be "physically" ready to
restart by Sept. 22 and the other could be refueled and ready
by mid-October. But NRC officials said meetings probably will
be needed to explore Dominion's inspection process.
"A fundamental question we have based on the reanalysis is
how are you going to look at your design basis for earthquakes
going forward?" said Joe Giitter, director of the NRC's
licensing division for operating reactors.
SHAKEN, BUT NOT BROKEN
Japan's nuclear disaster at the Fukushima Daiichi plant --
overwhelmed six months ago by an earthquake and tsunami -- put
quake risks at the forefront.
The NRC has said it plans to order all U.S. plants later
this year to update their earthquake risk analyses, a complex
exercise that could take two years for some plants to complete.
The North Anna quake shows the need for the nation's 104
aging reactors to reevaluate earthquake risks using up-to-date
geological information, said Majid Manzari, an engineer at
George Washington University who studies quake impacts.
A former chairman of the NRC said he expects the broad
review ultimately will impact most nuclear plants along the
U.S. East Coast.
"I think what the East Coast earthquake demonstrated is the
design parameters might be changing," said Dale Klein, a
mechanical engineer at the University of Texas.
Nuclear power critics have seized on the North Anna quake.
"We need a seismic shift in the way in which these plants are
protected from earthquakes or other natural disasters." said
Representative Edward Markey, a Democrat from Massachussetts.
(Additional reporting by Eileen O'Grady in Houston and Timothy
Gardner in Washington; Editing by Jim Marshall, Sofina
Mirza-Reid, Bob Burgdorfer and David Gregorio)