Delicate process of refueling York, Pa.-area nuclear power plant begins
York Daily Record, Pa. --Sep. 26
Sep. 26--High above Peach Bottom Atomic Power Station's spent nuclear fuel pool, a team of plant workers dressed in radiation-resistant white coveralls and yellow rubber gloves ride a motor-driven platform.
The purple-blue glow of the 12-foot-long spent fuel assemblies signals the
shock wave of photons emitting from the rods.
The metal arm slowly pulls the bundles rods through the water toward its
predetermined slot at the bottom of spent fuel pool as workers eye the process
from above.
The plant is in the thick of its Unit 2 refueling and maintenance outage.
Plant workers labor around-the-clock in 12-hour shifts to finish their assigned
jobs as efficiently as possible.
The power station shut down its Unit 2 reactor Sept. 14 for refueling and
maintenance that continues today and into this week.
Held every two years, the outage is an opportunity for the plant to repair
and replace various machinery and to work on the main turbine generator.
For roughly three weeks, Peach Bottom Township plays host to an army of
trained workers and contractors whose goal is to get a nuclear plant refueled
and back online.
Save for the full-body radiation detectors, the main entrance to the plant
looks more like the top floor of a hospital than a nuclear power plant.
Workers dressed in all-cotton, aqua-blue scrubs enter and leave the building
by way of detectors that sound should a person contain a trace of radiation.
Cotton tends not to pick up radon, but synthetic materials such as polyester
can trap detectable amounts of radiation in their fibers.
Pager-shaped dosimeters hang from the neck of each worker and will beep if
surrounding radiation reaches dangerous levels.
The Nuclear Regulatory Commission's occupational exposure limit is five rem a
year, said Diane Screnci, an NRC spokeswoman. A rem is a measure of radiation,
and a single dose of 500 rem would kill a human.
One task during the outage: monitor workers' exposure to radiation since
personnel perform jobs in areas not visited when the plant is online, said
Robert Braun, site vice president of Peach Bottom Atomic Power Station.
"Every single job has a dose estimate," he said. "We take
action to minimize people's exposure."
Upstairs, senior staff members man the outage control center -- a
round-the-clock headquarters that monitors the outage and is second only to the
plant's main control room.
Two large Gateway-brand monitors give plant personnel a bird's-eye view of
refueling operations and the spent fuel pool.
Power station personnel start to plan the outage about two years in advance,
said Ken Langdon, the director of work management for Peach Bottom Atomic Power
Station.
Members of senior management run the outage, review lesson-learned reports
from previous outages and resolve any issues prior to shutdown.
A goal is to run the outage efficiently and to reduce the number of hours and
days a plant is down, Braun said.
The longer a reactor is shut down, the less power flows from the plant to the
PJM Interconnection power grid.
A loss in power from Peach Bottom's plant translates into a loss of revenue
for its parent company, Exelon Nuclear.
Other power plants must pump out a few extra megawatts to help make up for
energy lost to the refueling, said Joe Patterson, spokesman for PJM
Interconnection.
Aside from the financial factors, the plant is at a safer level when it is
online compared to when the reactor is shut down.
All systems, including those that are safety-related, function when the
reactor is at full power, said David A. Lochbaum of the Union of Concerned
Scientists, a Washington, D.C.-based nonprofit environmental group.
Power plants typically shut down a number of their systems and their back-up
counterparts to allow workers into areas that are usually off limits, he said.
For example, a reactor's high-pressure systems that provide cooling are taken
offline since that section of the plant is not under high pressure during
refueling, Screnci said.
Emergency reserve operations remain in place that can activate the
high-pressure system if needed, she said.
A key factor in any refueling outage is to ensure that the current and spent
fuel remain submerged in coolant, Langdon said.
Plant workers and senior staff are responsible for monitoring the water
levels within the reactor cavity, he said.
That cavity is completely filled with water at the time of an outage.
Locked away in the vital area of the plant is the second reactor and its
neighboring spent fuel pool.
The floor of the 53-foot-deep pool is covered in underwater racks -- similar
in appearance to a utensil holder in a dishwasher -- that house the spent fuel
bundles.
A small narrow gate dubbed the cattle chute links the second reactor to its
spent fuel pool.
Racks nearest to the chute hold the new fuel assemblies for easy transfer
into the reactor.
Those bundles have more of metallic veneer than their used, blackened
counterparts.
Heat and constant exposure to chemically treated coolant within the reactor
cause the rods to blacken, said Joseph M. Clawson, a reactor services outage
manager.
Prior to the outage, between 260 to 280 new fuel bundles arrived at the plant
on a flatbed truck and were promptly hoisted into the pool.
Plant workers will replace roughly one-third of the second unit's spent fuel
before the reactor goes back online.
The fuel bundles are not exposed to radiation until they are in the reactor,
and are safe to handle before they are used to power the plant, Braun said.
"You can be behind a truck carrying these assemblies and not know
it," he said. "The truck might have a placard on it, but that's about
it."
While chemically treated water is used to keep the fuel cool, the liquid also
acts as a shield against radiation.
Uncovered nuclear fuel would quickly overheat and begin to melt down,
Lochbaum said.
Workers exposed to uncovered fuel would receive a lethal dose of radiation
within seconds.
Spent fuel submerged in more than 30 feet of water exposes workers to
radiation levels less than what they would get during an X-ray, Lochbaum said.
Engine parts, some the size of a Harley-Davidson motorcycle, litter the
turbine deck of the plant's second reactor.
Like Lilliputians who have secured the fallen Gulliver, workers scale the
tractor-trailer-sized main turbine generator -- on the lookout for parts that
may need to be repaired or replaced.
The turbine generator is powered by 19 valves that routinely open and close
to feed steam into the engine, Langdon said.
During the current outage, Peach Bottom Atomic Power Station will rebuild
seven Unit 2 steam valves as part of the plant's preventive maintenance
programs, he said.
One of the valves has a deficiency and workers must repair a worn seal before
the equipment can resume service, Langdon said.
"It opens and closes a bit too much," he said.
Overseeing all the tasks are two resident NRC inspectors whose job it is to
ensure the plant runs safely, Screnci said.
The commission holds the power to shut down both reactors if it believes the
plant is not being operated safely.
In 1987, the NRC ordered the plant to shut down after it discovered that some
control room staff working the 11 p.m. to 7 a.m. shift had taken periodic naps
or had been not attentive to duties.
At the time, one of the reactors was shut down for refueling. The other unit
stopped operation within three days of the NRC's order. The commission allowed
both reactors to retain full power on Oct. 15, 1989, Screnci said.
"A plant does not typically need NRC approval to restart after a
refueling outage," she said.
When a Peach Bottom Atomic Power Station reactor shuts down, Roula Skouras is
ready with extra food and beverages.
Each September, Skouras, of the Peach Bottom Inn, keeps additional supplies
on tap to deal with the more than 1,000 additional laborers the power station
calls in to work its refueling outage.
Peach Bottom Atomic Power Station's usual number of workers balloons from
around 700 people to roughly 2,000 during a refueling.
The station calls in a mix of plant workers, staff on loan from nearby
nuclear installations and contractors.
The Peach Bottom Inn's 24 rooms are booked four to five months in advance,
said Skouras, the inn's manager.
"This is our sixth outage, and we are prepared," she said.
"It's good for business. Some nights, it's standing-room only."
Skouras said she recalls the first time the Peach Bottom Inn had to deal with
the challenges of a refueling outage.
Hotel staff made early morning trips to area food suppliers to help keep
freezers and storage lockers stocked, she said.
"We learned the hard way that first year," Skouras said, "We
had a lot of late-night deliveries."
The workers must adhere to strict federal and company regulations before they
can work an outage.
Workers must pass a rigorous series of background checks, exams and
fitness-for-duty tests before they enter the plant, said Dana Melia, spokeswoman
for Exelon Nuclear.
"We would not be able to do the outage without those people," Braun
said.
GLOSSARY
--Dosimeter -- A small portable instrument used to measure and record the
total accumulated personnel dose of ionizing radiation.
--Spent nuclear fuel -- Fuel that has been removed from a nuclear reactor
because it can no longer sustain power production for economic or other reasons.
--Turbine -- A rotary engine made with a series of curved vanes on a rotating
shaft, usually turned by water or steam. Turbines are considered the most
economical means to turn large electrical generators.
--Shutdown -- A decrease in the rate of fission and heat production in a
reactor, usually by the insertion of control rods into the core.
--rem -- The acronym for Roentgen Equivalent Man is a standard unit that
measures the effects of ionizing radiation on humans.
--Fuel rod -- A long tube that holds material used to power a nuclear
reactor. Fuel rods are assembled into bundles called fuel elements or fuel
assemblies.
--Control room -- The area in a nuclear power plant from which most of the
plant's power production and emergency safety equipment can be operated by
remote control.
--Outage control center -- The main area used to monitor refueling outage
activities. The plant has staffed the center to handle emergency shutdowns.
Source: Nuclear Regulatory Commission; Exelon Corp.
AT A GLANCE
Peach Bottom Atomic Power Station has two boiling water reactors that
jointly, at full power, produce more than 2,300 megawatts of energy a day.
Exelon Nuclear and PSEG jointly own the plant.
In 2003, the station provided more than 18 million megawatts of emission-free
electricity to the region -- enough energy to power 2 million homes.
Power flows from the plant to the PJM Interconnection grid.
Based in Valley Forge, PJM Interconnection controls a series of power grids
fueled by natural gas, oil, nuclear power and coal.
All of York County's electricity comes from the PJM Interconnection grid.
Between June 25, 1998, and July 1, Peach Bottom Atomic Power Station has
operated 10 million hours without a lost-workday incident.
Its Unit 2 and Unit 3 reactors came online July 5, 1974, and Dec. 23, 1974,
respectively.
Last year, the Nuclear Regulatory Commission granted license extensions for
Unit 2 and Unit 3 to run until 2033 and 2034, respectively.
-----
To see more of the York Daily Record, or to subscribe to the newspaper, go to
http://www.ydr.com .
(c) 2004, York Daily Record, Pa. Distributed by Knight
Ridder/Tribune Business News. For information on republishing this content,
contact us at (800) 661-2511 (U.S.), (213) 237-4914 (worldwide), fax (213)
237-6515, or e-mail reprints@krtinfo.com. EXC,