Watts Bar Unit 2 Nuclear Plant Synchronized to Power Grid

The Tennessee Valley Authority (TVA) reached another milestone on June 3 when operators at Watts Bar Unit 2-the nation's newest nuclear power plant and the first added to the fleet in 20 years-synchronized its generator to the power grid, generating electricity from the plant for the first time (Figure 1).

1. Reactor Operator Bill Hahn synchronizes Watts Bar Unit 2 to the TVA power grid on Friday, June 3, 2016. Courtesy: TVA

Watts Bar Unit 2 has had a long and storied history. Ground was broken for the plant in 1973. However, construction was suspended in 1985 due to slower electricity demand growth, rising construction costs due to inflation and new regulatory requirements stemming from the accident at Three Mile Island in 1979, and regulatory concerns throughout the TVA nuclear fleet. At the time, Unit 2 was estimated to be about 80% complete with a total investment of about $1.7 billion.

In the years that followed, various pieces of equipment, such as pumps, motors, and valves, were salvaged for use in Watts Bar Unit 1 or in Watts Bar's sister plant, Sequoyah. A detailed scoping, estimating, and planning study completed in 2007 found Watts Bar Unit 2 to be effectively 60% complete and it was estimated that the unit could be finished in about 60 months at a cost of about $2.5 billion.

Construction resumed on Unit 2 in 2008, but the cost and time estimates have proven to be optimistic. On May 23, 2016, the reactor achieved initial criticality, which is when the reactor's neutron population remains steady from one generation to the next and the nuclear fission chain reaction is self-sustaining for the first time. With the unit now synced to the grid, reactor operators have begun an initial test run to collect performance data (Figure 2).

2. Reactor Operator Eric Silvers monitors the Unit 2 control room screen displaying 49 MW of electric output. Courtesy: TVA

"This is another major step in fully integrating Watts Bar Unit 2 as the seventh operating unit in TVA's nuclear fleet," said TVA Chief Nuclear Officer Joe Grimes. "It is rewarding to see TVA taking the lead on delivering the first new nuclear unit of the 21st century and providing safe, affordable and reliable electricity to those we serve."

The next step is full-plant testing of systems and controls at increasing reactor power levels up to 100% power (1,150 MW). Those tests will be repeated multiple times to ensure the plant operates safely as designed. The TVA expects Watts Bar Unit 2 will be placed in commercial operation this summer at a total estimated project cost of $4.7 billion.

-Aaron Larson, associate editor (@AaronL_Power, @POWERmagazine)

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