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Regional News
| Article published Friday, August 1, 2003
COOLING-SYSTEM FLAW ADDRESSED, UTILITY
SAYS
NRC flags Davis-Besse for another
safety glitch
By TOM
HENRY
BLADE STAFF WRITER
The faulty design of Davis-Besse’s emergency
core cooling system - a problem with the containment sump that was
overlooked since the nuclear plant opened in 1977 - was tentatively
classified yesterday as a problem that had "substantial safety
significance," government regulators said.
The Nuclear
Regulatory Commission issued a preliminary "yellow" finding largely
on the belief that the system in place would have worked if the
plant had had a small loss-of-coolant accident - not a more
potentially devastating one caused by a medium or large break in the
coolant system, Jan Strasma, a NRC spokesman, said.
The
utility has 10 days to respond.
FirstEnergy does not plan to
contest the NRC’s yellow finding. "We’re pleased to have that issue
behind us," Richard Wilkins, a company spokesman, said.
The
Three Mile Island accident near Harrisburg, Pa., in 1979 - the most
notorious in U.S. nuclear history - is widely viewed as a small
loss-of-coolant accident, according to David Lochbaum, a nuclear
safety engineer for the Union of Concerned Scientists and a
nationally known industry watchdog.
A yellow finding is one
notch below the most serious issued by the NRC, its "red" finding
for problems deemed to be of the highest safety magnitude. The NRC
issued a red finding against FirstEnergy on Feb. 25 for letting
Davis-Besse’s reactor head become so thinned by rust that it nearly
burst and allowed radioactive steam into the plant’s containment
building.
"The reason why a small break would have less
impact is simply because the force of the steam and water would be
less. It would be greater for the larger [loss-of-coolant]
accidents, where there would be more potential to dislodge debris,"
Mr. Strasma said.
NRC and nuclear insiders have differing
theories about whether a rupture in Davis-Besse’s reactor head would
have led to a small, medium, or large loss of coolant water. The
head was found March 6, 2002, in a perilously-thin condition: A lack
of maintenance had allowed all but two-tenths of an inch of the
six-inch-thick reactor head to be rusted away in one spot, where the
liner had started to buckle and crack.
The longstanding
problem with Davis-Besse’s containment sump and its associated pair
of high-pressure injection pumps was diagnosed by FirstEnergy last
fall, in part because the company has done a more thorough analysis
of plant systems during the extended outage. The plant has been idle
since Feb. 16, 2002.
The sump, which would be used to collect
water off the containment floor in the event of a line break, was
deemed faulty because of its propensity to get clogged by floating
debris.
That has the potential of making the safety system
inoperable. Once purified water in a holding tank is used up, pumps
would have to switch over to sump water. The NRC’s concern was that
the sump would not filter out all debris and that bits of material
would pass through, breaking down the high-pressure injection pumps.
If that were to happen, operators might not be able to keep
re-circulating water over the hot reactor and prevent a meltdown,
officials have said.
"For small loss-of-coolant accidents,
the safety systems rely on the tank. You never really have to swap
over and use the sump water," Mr. Lochbaum said. "The system that
needed to work [in the event of a medium or large line break] was
impaired."
The utility has responded to the sump problem by
redesigning it and installing a strainer that should filter out
debris. It has removed unqualified coatings in the containment area.
Unqualified coatings were cited by the NRC as inadequate because of
their potential to become debris in the event of an
accident.
The yellow finding will not likely result in a fine
because it does not appear to be a willful violation. It is a
technical violation related to the plant’s design, Mr. Strasma
said.
The NRC also cited an event in May that resulted in
three inches of water flooding Davis-Besse’s turbine building
because workers did not perform their jobs adequately.
The
flooding started after workers tried to refill the plant’s
circulating water system on May 15. One employee failed to follow an
assigned procedure, allowing water to pass through valves that were
supposed to be closed. Control-room operators were alerted by three
alarms, but failed to respond, Mr. Strasma said.
The mess did
not result in a safety threat. But the NRC is concerned because the
agency has told FirstEnergy for months that it expects the company
to be more diligent and instill a greater questioning attitude among
its employees, he said.
FirstEnergy has enhanced training for
the employees in question, on both the procedure and the need for
identifying problems, Mr. Wilkins said.
For earlier
stories on Davis-Besse, go to
www.toledoblade.com/davisbesse.
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