FWD: Tornado Hits Nuclear Power Plant

["Jaramillo, Eric D" <edjaram@sandia.gov>]

Nuclear Plant Survives Tornado Hit

.c The Associated Press

 By MIKE MOKRZYCKI

OAK HARBOR, Ohio (AP) - The atomic power plant's control room grew dim.
Instrument lights flashed red as the storm raging outside knocked out two   
of
three power lines. Then came the urgent warning from security: Cameras   
showed
three distinct funnel clouds taking dead aim.

Moments later the last power link was cut, and the control room briefly   
went
dark. The plant computer failed. A ``red phone'' hot line to Washington   
went
dead.

On June 24, the Davis-Besse Nuclear Station on Lake Erie took the worst   
direct
hit by a tornado ever weathered by a U.S. atomic plant. The 900-megawatt
reactor shut down automatically and no radiation leaked, largely because   
of
the staff's quick, competent responses and backup equipment.

But for 41 tense hours, an array of equipment problems complicated   
efforts to
keep the reactor's radioactive fuel core cool and to communicate inside   
and
outside the plant. Among the problems:

The tornado severed fiber optic lines and knocked out the plant's main   
phone
system. The federal hot line, linked directly to the plant, also failed.   
A
microwave-based phone system provided limited service but slowed plant
officials' efforts to notify local and state emergency managers that they   
had
declared an alert - the second of four increasingly serious emergency
classifications.

Because of a faulty switch, a key safety display went black for two hours
immediately after the tornado. Heat knocked it out again the next   
afternoon.

Two locomotive-sized emergency diesel generators provided power to avert   
a
total plant blackout, but temperatures in the room housing one generator   
rose
2 degrees over the operating limit when a vent got stuck the afternoon   
after
the storm.

``For a few minutes your heart goes up into your throat,'' said Bob   
Donnellon,
the plant's emergency director when the generator alarm sounded. ``But   
you
have a gut feeling that it's OK. Your guys confirm it. Your comfort level
comes back a bit.''

Hours later, as the plant was switching back to offsite power, the second
generator shut down a few seconds early because of a faulty relay.

Plant managers also worried about rising temperatures in a 23-foot-deep   
pool
that cools spent reactor fuel. The temperature reached 140 degrees -   
roughly
the point where evaporation would increase - but enough offsite   
electricity
returned to power the cooling pumps.

In the end, public safety was never threatened, according to the Nuclear
Regulatory Commission. The NRC, which activated its emergency command   
post
outside Washington and alerted the White House and other U.S. and
international agencies, is preparing a report on the equipment problems.   
The
agency's senior inspector at Davis-Besse, Steve Campbell, said he was   
aware of
no operator error throughout the episode.

An industry watchdog group complimented the plant staff.

``They were faced with a lot of challenges they shouldn't have had to   
face,
and they met those challenges very well,'' said David Lochbaum of the   
Union of
Concerned Scientists. ``They're trying to gain all the lessons learned   
from
this event to make things even better in the future.''

One lesson will be to alert plant workers about threatening weather. The
National Weather Service issued a severe thunderstorm warning at 7:48   
p.m. A
tornado warning cleared at 8:44 p.m. With winds of 80-90 mph on the   
leading
edge of the storm knocking out power all over Ottawa County, a regional
dispatcher for Toledo Edison neglected to pass along both warnings to the
Davis-Besse control room.

Inside the fortified command center, workers could not hear the roaring   
winds
or see the sickly yellowish sky. Their first warning was a phone call   
from an
off-duty colleague who lives nearby, at 8:36 p.m., NRC spokesman Jan   
Strasma
said.

Less than 10 minutes later, a guard monitoring outside cameras from the
plant's security room saw three funnel clouds converging into one over   
the
plant and called the control room, said Jim McGee, the plant supervisor   
that
night.

Davis-Besse security analyst Jim Theisen went outside to check conditions   
and
saw water and debris being sucked out of the base of the plant's cooling
tower. ``There was large chunks of stuff coming out,'' he said.

The tornado destroyed the plant's wind gauge; weather service forecaster   
Larry
Gabric estimated the twister's winds at almost 160 mph.

Most seriously, the tornado ripped power cables from their connectors in   
the
electrical switchyard - in essence the fuse box for the entire plant.

In the control room, McGee watched the indicator for the last power link   
go
from green to red. The room briefly went dark except for instruments and
emergency lighting.

``For those few seconds everyone's just standing still,'' McGee said.   
``And
then the diesels come up, and everyone goes on with their tasks.''

Even so, as the backup electricity relighted the control room, the safety
display stayed black. This was a system the NRC ordered installed in U.S.
nuclear plants after the partial meltdown in 1979 at Pennsylvania's Three   
Mile
Island reactor, where control-room confusion contributed to the nation's   
worst
nuclear accident.

The 21-year-old Davis-Besse plant has a similarly designed reactor to   
Three
Mile Island's. It had serious operational problems in the 1980s but is   
now
considered one of the better-run of 107 operating nuclear plants in the
country.

Plant officials declared the emergency over at 1:58 p.m. on June 26 after
restoring a second power line.

Davis-Besse managers said the emergency proved the value of their   
frequent
accident drills.

``We may complain about the emergency response guys and how much they   
make us
drill, but we don't now,'' Donnellon said.

AP-NY-07-18-98 1300EDT