You wouldn't know it from the bland pronouncements of the Nuclear
Regulatory Commission (NRC), but the U.S. nuclear industry just had its
closest brush with disaster since the 1979 Three Mile Island accident. The
Davis-Besse nuclear power plant, located about 30 miles east of Toledo,
Ohio, was operating with a rust hole in the top of its reactor pressure
vessel -- a hole wide and deep enough to put your fist into. All that was
left to contain the reactor's highly pressurized supply of cooling water
around the reactor core was a three-eighths inch liner of stainless steel,
and the liner had started to bulge ominously. If the liner had burst, it
would have drained cooling water vital for safety and also threatened the
reactor's emergency shutdown system.
The plant operator's neglect is bad enough. If this had occurred in
Russia, we would be saying it could never happen here. Equally disturbing
is the NRC's barely audible response.
The preliminary report of FirstEnergy, the nuclear plant owner, details
what happened. During a routine refueling shutdown in February, the
company inspected several dozen nozzles to check for cracks, as required
by the NRC. The nozzles, located on the head of the reactor vessel, permit
control rods to enter the vessel to shut down the reactor, quickly if
necessary. A workman discovered the rust hole by luck -- when he happened
to bang into one of the control rod tubes coming out of the top of the
reactor and it moved. If the reactor had gone back into operation, as it
very nearly did, the consequences could have been enormous in terms of
public safety as well as the future of the nuclear industry.
It turned out that corrosion had reduced 70 pounds of steel, half a
foot thick, to rust. The corrosion was caused by boric acid on the outside
of the head. How did the acid get there? The water inside the reactor
vessel contains dissolved boric acid, which is used to assist reactor
control. Because boric acid corrodes carbon steel, the reactor vessel's
interior is lined with stainless steel. The boric acid is not supposed to
get to the vessel's exterior, which remains vulnerable to corrosion. But
at Davis-Besse the reactor's water leaked through cracks -- it still isn't
clear which ones -- and created a boric acid crust on the outside of the
reactor head.
This accumulation and damage doesn't happen overnight. The company
report explains the hole hadn't been found earlier because, "Boric acid
that accumulated on the top of the [Reactor Pressure Vessel] head over a
period of years inhibited the station's ability to confirm visually that
neither nozzle leakage nor vessel corrosion was occurring." In plain
English that means that the company watched the boric acid crust cover an
increasing area of the head for years and did nothing about it. That's not
all. Some of the reactor vessel rust became airborne and clogged the
reactor building's air filters. The filters had previously been changed
monthly, but from 1999 on they had to be changed every other day. The
company's report says the possibility of corrosion "was not recognized as
a safety significant issue by the staff and management of the plant."
Obviously the NRC, which had inspectors on site, did not recognize it
either.
How important is this? The reactor vessel head resembles a rounded lid
that is bolted to the vessel. It's about 15 feet in diameter. The reactor
vessel and the vessel head are designed and manufactured with exquisite
care from special steel a half-foot thick (with the thin liner of
stainless steel). The vessel and head of every reactor have to be
monitored throughout their life to make sure that radiation has not caused
the metal to become brittle. This is vital because the NRC licensed the
plant on the assumption that a break in the reactor vessel is not
credible. As a result, the reactor's safety analysis does not deal with
breaks in the vessel wall. The reactor's emergency actions operators are
trained to cope with breaks in pipes, not the vessel. Some safety systems
might work for such a break; then again they might not. The problem was
not studied. There would likely be unforeseen complications.
An obvious complication would involve malfunctioning of the control rod
system that is supposed to stop the chain reaction in an emergency. There
is no backup to the control rods for immediate shutdown. The plant's
safety analysis considers the possibility that a limited number of rods,
out of several dozen, could fail to drop. The control rod adjacent to the
rust hole would have been one of these. But what about the damage that
might be caused to other control rod drives above the head if a hole in
the vessel unleashed a jet of steam and water coming out of the
pressurized vessel? A telling sign that the industry understands the
seriousness of the Davis-Besse problem is the silence from the Nuclear
Energy Institute, the industry's lobbying arm, which is usually quick to
spin a nuclear story. All in all, what happened at Davis-Besse was a
narrow escape.
But that isn't the way the NRC has described it in public. The agency's
spokesperson told the media that the rust hole didn't pose a safety
threat. If the last bit of metal had failed and "allowed steam to escape,"
the NRC official said, safety systems would have immediately cooled the
reactor. Anyway, he said, there would have been no danger to the public.
"It's only when you get into the what-ifs that you would have had any
leakage from the reactor cooling system." The man was talking through his
hat. In reality, the NRC doesn't know what would have happened because the
possibility has been considered too unlikely to plan for.
The failure to face up to reality reflects an unhealthy situation. Such
spokesmen say what their bosses want them to say, and for several years,
the NRC has been knocking itself out to please the industry. The situation
worsened in 1998 when the NRC's Senate oversight committee, Environment
and Public Works, with strong prompting from the industry association,
threatened the NRC with a sharp budget cut. The NRC chairman got the
message and revamped the agency's regulatory approach along the lines
suggested by the industry. The current commission has by and large
continued the same approach, but with a less experienced senior staff. The
previous chairman had forced the resignation of the agency's most
experienced and competent top officials, who had showed an unwelcome
independence of mind.
Just before Davis-Besse's problem surfaced, the NRC gave the plant its
quarterly rating under the new rating system. Davis-Besse got the top
grade in all 18 categories. From my experience in two terms as an NRC
commissioner, during which I visited most of the plants, including this
one, I find it inconceivable that everything was fine at Davis-Besse
except for one corrosion hole in the reactor vessel. If the plant managers
let this problem go, they must have let others go, too. People working in
nuclear plants are pretty smart and generally want to do a good job. But
they stop asking questions about things that aren't right when they know
what answer management is going to give them. At that point, danger lurks.
The NRC has investigated and has now asked other plants to check to
make sure they are not suffering from the Davis-Besse problem, but on an
unhurried schedule. To a greater extent than ever before we are relying
for nuclear safety on the self-regulation of the nuclear operators. Most
of them have done a good job, steadily improving their performance. But
there are limits to the idea put forward by the industry that
post-deregulation financial pressures make for better safety because the
operators want to protect their investment. As we know, short-term bottom
line orientation also leads some to overreaching, defer necessary
modifications or neglect maintenance. Congress and NRC management need to
acknowledge that private and public incentives differ.
The late Morris Udall, who as chairman of the House Interior Committee
was the principal congressional overseer of the NRC in its eary years,
used to say that a forceful and respected NRC was an essential condition
of nuclear power. It is still true.
Victor Gilinsky, a Washington-based consultant on energy, was an NRC
commissioner from 1975 to 1984.
Outlook
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