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Regional News
| Article published Tuesday, February 25, 2003
NRC holds to inspection of all Besse-type reactor
heads
By MICHAEL WOODS
BLADE SCIENCE
EDITOR
ROCKVILLE, Md. - A top U.S. Nuclear Regulatory
Commission official expressed concern yesterday that the rust
problem that nearly ate through the reactor head at Davis-Besse
still may be a threat at other nuclear power plants.
Brian
Sheron, an associate director of the agency, raised the topic at the
end of a meeting called to inform nuclear power plant operators
about a strict new inspection regimen ordered in Davis-Besse’s
wake.
During the session, the NRC rejected an industry effort
to redefine "100 percent" in a key clause in the order, issued Feb.
11 to owners of nuclear power stations with reactors similar to
Davis-Besse’s.
It requires a visual inspection of 100 percent
of the bare metal on the reactor pressure vessel head.
That
is the top of the thick steel container that holds tons of
radioactive material under high pressure.
FirstEnergy, which
owns the Davis-Besse Nuclear Power Station, found a football-sized
hole in the steel container in March, the result of a leak of
corrosive acid that went uncorrected for years. NRC described the
episode as the most serious safety lapse in recent
history.
The Nuclear Energy Institute, an industry group in
Washington, quickly objected to the 100-percent inspection
requirement. Alexander Marion, the group’s director of engineering,
argued that workers at many nuclear plants are unable to see 100
percent of the reactor vessel head surface because of
obstructions.
Complete inspections would be unnecessarily
costly, with owners required to remove and replace insulation and
other components during plant shutdowns, Mr. Marion
suggested.
Mr. Marion asked NRC to define "100 percent" in
the new order according to an obscure clause in the agency’s
existing regulations.
It would let owners get by with
inspecting "essentially 100 percent" of the reactor vessel head,
which the regulations define as at least 91 percent.
"With
the order, 100 percent does mean 100 percent," NRC’s Alan Hiser told
Mr. Marion. "There’s nothing intended there to allow lesser
inspections."
"Unreasonable and burdensome," Mr. Marion later
grumbled, referring to certain requirements in the order.
NRC
staff, however, said nuclear power plant owners could apply for
"relief" from provisions that were unusually difficult to comply
with.
Mr. Sheron said waiver requests would be considered on
an individual basis. Some, he said, would require approval from the
top official in NRC reactor regulation division.
The new
order also requires plant operators to do additional inspections for
leaks in plumbing connections located above the reactor pressure
vessel. Water flowing through the pipes contains boric acid, the
corrosive material that ate into the Davis-Besse pressure
vessel.
Mr. Sheron said boric acid leaks at other nuclear
power plants continue to bewilder and concern NRC
officials.
Most plants, he said, have some "unidentified
leakage" of the solution of water and boric acid used to cool the
nuclear reactor. It’s categorized as "unidentified leakage" because
nobody is certain exactly which pipe fittings or other components
are leaking.
Ideally, the leakage amounts to less than one
gallon per minute. But some plants lose 10 gallons a minute,
amounting to huge quantities of boric acid each year, he
explained.
"The question we scratch our heads about is where
that boric acid is going," Mr. Sheron said.
At Davis-Besse,
it accumulated in a difficult-to-see spot on the reactor pressure
vessel, quietly damaging the vessel.
Mr. Sheron said the NRC
is in the early stages of considering measures that would require
utilities to identify the leaks and account for each pound of lost
boric acid for added safety assurance.
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