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Regional News
| Article published Wednesday, May 21, 2003
DAVIS-BESSE
Cause of
corrosion stumps regulators Report cites degree of
uncertainty
By TOM HENRY
BLADE STAFF
WRITER
OAK HARBOR, Ohio - FirstEnergy Corp.’s
explanation for the unprecedented corrosion of Davis-Besse’s reactor
head is "plausible" at best, according to the Nuclear Regulatory
Commission.
Agency officials said they accept the utility’s
theory for what happened, but believe there are "some uncertainties
and inconsistencies" in the sequence of events from a technical
standpoint. The comments are contained in an attachment to an
inspection report that covered a recent seven-week
period.
During a refueling outage, workers discovered boric
acid had burned through 6 inches of steel, leaving two-tenths of an
inch of stainless steel to hold back the reactor’s enormous
pressure.
FirstEnergy had told the NRC that it underestimated
the volume of acid that had collected under the reactor’s insulation
and the ensuing magnitude of the corrosion.
NRC officials
said they are befuddled why similar corrosion has not occurred at
other nuclear plants that had similar control rod nozzles that leak
corrosive boric acid from their reactors.
"In short, the
degree of uncertainty and the number of unknowns regarding the
progression of events that led to the development of the cavity at
Davis-Besse limits the ability to qualify the technical root cause
report beyond "plausible" at this time," the NRC
said.
Davis-Besse has been shut down since Feb. 16, 2002. Its
original reactor head was declared the most corroded in U.S. nuclear
history
That head has since been replaced by one from a
never-used nuclear plant in Midland, Mich., a move supported by the
NRC.
Beginning in 1988, the agency has warned nuclear plants
to be on guard for reactor-coolant leakage and to clean popcorn-like
acid crystals off reactor heads. FirstEnergy had a "persistent layer
of boron" on top of its reactor head since at least 1996. Corrosion
may have spread faster than expected if a sheen of acid had been
allowed to form and mix with oxygen inside the containment building,
the NRC said.
Richard Wilkins, FirstEnergy spokesman, said
the nuclear industry also wants to know what accelerated the
corrosion rate at Davis-Besse.
David Lochbaum, Union of
Concerned Scientists nuclear safety engineer, said the questions
surrounding Davis-Besse should have a lasting impact as the NRC
revamps its inspection requirements.
For earlier
stories on Davis-Besse, go to www.toledoblade.com/davisbesse
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