AP/Tennessee Valley Authority file photo|
The Tennessee Valley Authority restarted its Unit 1 reactor at Browns Ferry Nuclear Plant on Tuesday.
Unit 1 up
Browns Ferry reactor splitting
atoms again after 22-year shutdown
By Eric Fleischauer
Eric@decaturdaily.com · 340-2435
For the first time since 1985, uranium atoms are splitting at Browns Ferry Nuclear Plant Unit 1. The restart began Tuesday at 12:28 a.m.
"This is the newest old plant in the nation," said Browns Ferry spokesman Craig Beasley.
Unit 1 may begin generating electricity as early as this week on a temporary basis as testing continues. The Tennessee Valley Authority does not expect a permanent connection to the power grid for at least two weeks.
The Nuclear Regulatory Commission authorized the restart May 15 after an inspection that consumed 30,000 staff hours. Refurbishing the nuclear plant took five years, 15 million man-hours and $1.8 billion.
The restart marks the first increase in U.S. nuclear generating capacity since 1996, when TVA activated Watts Bar Nuclear Plant.
When on line, TVA said, Unit 1 will provide 1,155 megawatts of power. That's enough to power 650,000 typical homes. The plant's three units combined will be able to generate enough electricity for 1.8 million homes.
Over the next several days, TVA will gradually increase the unit to full power. Beasley said it should increase to 35 percent Wednesday or Thursday. Workers will conduct numerous tests after each increase in power.
"We've come too far now to rush through these tests," Beasley said. "All of that testing goes into ensuring that the reactor and its systems are going to run the way it's designed, which is safely."
The plant is on the Tennessee River, about nine miles from downtown Decatur and eight miles from downtown Athens.
The Unit 1 restart will add more than 100 employees on an ongoing basis, bringing the total number of Browns Ferry employees to 1,250. Its annual payroll is $73 million.
"Restart" occurred when TVA, partially withdrawing control rods from the core, achieved a self-sustaining chain reaction within the reactor.
The restart required numerous changes in the plant.
"It's got new instrumentation and controls," Beasley said. "A lot of the fundamentals are still there. You don't change out a reactor or anything like that, but in terms of the piping and the instrumentation and the controls and the cables, that's brand new stuff."
The Unit 1 improvements included 200 miles of electrical cable, 35 miles of conduit, eight miles of pipe and 189 tons of structural steel. TVA also replaced the reactor feedwater pumps and modified the fire-protection system.
Beasley said TVA decided to restart Unit 1 because of increasing energy consumption in North Alabama. He said those increases continue at about 2 percent annually.
When the plan for a restart began in 2002, TVA projected it would pay for itself in seven or eight years.
"Right now the predictions are that this unit can pay back its restart costs in four or five years," Beasley said. "The volatile cost of other fuels has made the payback much quicker."
Unit 1 produces energy through the fission, or splitting, of uranium atoms, TVA spokesman Terry Johnson explained. A neutron splits the large uranium atom into two smaller atoms, converting some of the atom's mass into energy and releasing more neutrons.
The neutrons released during fission strike other uranium atoms, causing a chain reaction.
Control rods in the reactor core absorb neutrons. While they are fully inserted, no neutrons are available to split the uranium atoms in the fuel. As the control rods are withdrawn, neutrons begin striking the uranium atoms, causing energy-producing fission.
"When you have a sustainable chain reaction, you have the same number of neutrons continuously in the reactor," Johnson said. "The reactor is 'critical' when you have the self-sustaining reaction," which is what TVA achieved Monday morning.
Unit 1 has had a troubled history. It came online in December 1973, but was shut down for a year after a fire caused major damage in 1975. The fire occurred when a worker was using a candle to check airflow through a temporary seal. The flame ignited the sealant, damaging cables related to the control of Unit 1.
TVA shut down all three Browns Ferry units in 1985 due to regulatory and management problems. It returned Unit 2 to service in 1991; Unit 3 restarted in 1995.
Browns Ferry was the largest nuclear plant in the world when it began operations.
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