UPDATE 3-Quake-hit US plant sees restart without retrofits

Fri Sep 2, 2011 10:47pm GMT
 

* Virginia plant near epicenter shut down after quake
    * No required modifications expected to prevent restart
    * But eventual changes expected in broader review-expert
    * Cosmetic damage found in containment structure at plant

    By Ayesha Rascoe and Roberta Rampton
    MINERAL, Va., Sept 2 (Reuters) - After a week of detailed
inspections, Dominion Resources Inc has not yet found any
severe damage that would prevent its quake-hit North Anna plant
from restarting, a senior official said on Friday.
    Dominion does not expect to have to do any major retrofits
before resuming operations at its plant, only miles from the
epicenter of last week's record earthquake in the Eastern
United States, said Dan Stoddard, the company's senior vice
president for nuclear operations.
    The force of the brief earthquake may have gone beyond the
design specifications for the two reactors -- the first time
that has happened for an operating U.S. nuclear power plant.
    Despite the lack of damage, the Virginia quake comes at a
sensitive juncture for the U.S. nuclear sector.
    A nuclear disaster in Japan that followed an earthquake and
tsunami in March prompted a major regulatory review in the
United States. Operators such as Dominion, Exelon ,
Entergy and PG&E have been assessing costs of
fixes to aging plants.
    This week, the Nuclear Regulatory Commission announced it
wants the country's 104 reactors to model earthquake risks
using updated data, the latest step in a decades-long process
that hasn't uncovered any "imminent" dangers but could
eventually result in expensive "backfits" for plants.
    "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, and a former
chairman at the NRC.
    "This is probably going to be plant-by-plant, and they'll
probably say, 'These are the requirements you now have to
meet,'" Klein said in an interview.VIRGINIA PLANT EXPECTS RESTART
    Reporters stepped over cracked floor tiles in the North
Anna plant's administrative building during a tour of the plant
on Friday, an example of the minor damage seen from the quake
that Dominion official Stoddard said speaks to the extra
engineering "safety margins" built into the plant.
    The most severe damage was to seals at the base of
high-voltage "porcelain bushings" that connect the plant's
transformer to the power grid, and Dominion has already begun
replacing the damaged equipment.
    Preliminary reviews indicated that while the ground may
have shaken more than the plant was designed to handle at
points during the earthquake, the strongest ground motions only
lasted a few seconds.
    "One acceleration for very short time over design
(specifications) does nothing to plant and that's consistent
with what we've seen," Stoddard said.
    "That tells me that earthquake was non-damaging ... and
that we have significant margin over and above the design of
the plant," he added.
    While the company stressed that the quake had done little
harm to the plant, officials declined to provide any specific
measurements of ground acceleration at the plant during the
historic tremor, saying the company's analysis is not yet
complete.
    Workers at the plant did find at small crack in an interior
wall within a containment structure at the plant. Officials
described it as "cosmetic" damage, however.
    The company will complete its analysis of the quake's
impact next week, but does not yet have a timeline for when it
will resume producing power -- something that will require
sign-off from the regulator.
    The Nuclear Regulatory Commission is also inspecting the
plant and its review is expected to take a few weeks.
    NRC Chairman Gregory Jaczko told Reuters on Thursday that
the regulator has not yet seen any sign of equipment damaged in
the quake, but he said it was too soon to say what changes the
regulator might require.
    There's nothing so far to suggest that the regulator would
move to permanently shut down the plant, said Nathan Ives, an
industry consultant with Ernst & Young.
    "I'd expect North Anna to be fully inspected and rigorously
inspected, but then to be back online, operating at capacity,"
said Ives, who formerly worked with the Institute of Nuclear
Power Operation, the industry's self-regulatory body.

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