TVA begins replacement of steam generators at Watts Bar nuclear plant

Staff photo by Tim Barber / Both cooling towers are in operation at Watts Bar Nuclear Plant in this file photo before the Unit 2 reactor was shut down this week for refueling and the installation of four new steam generators.
Staff photo by Tim Barber / Both cooling towers are in operation at Watts Bar Nuclear Plant in this file photo before the Unit 2 reactor was shut down this week for refueling and the installation of four new steam generators.

America's newest commercial nuclear reactor will be getting four replacement steam generators this spring during the biggest nuclear refueling and maintenance outage by the Tennessee Valley Authority in nearly a decade since similar steam generators were replaced at the Sequoyah Nuclear Plant.

TVA shut down the Unit 2 reactor at its Watts Bar Nuclear Plant this week to refuel the 1,150-megawatt reactor and to install the four 850,000-pound steam generators, which act as heat exchangers to convert water into steam from heat produced in a nuclear reactor core.

Although TVA has operated its newest reactor at Watts Bar for less than six years, the steam generators being replaced were built in the 1970s using designs that are nearly a half century old. The existing steam generators were found to be built with a metal alloy that has prematurely developed leaks and other problems at other nuclear plants.

The faulty equipment was installed at Watts Bar in the 1980s before TVA suspended work at the site due to cost overruns, employee safety concerns, and a drop in the projected power demand in the valley. TVA determined it would be too costly to replace the original steam generators when construction was resumed at Watts Bar Unit 2, so TVA operated with the original steam generators through a couple of earlier refueling outages before beginning the installation of the new units.

In 2014, TVA ordered the four new Westinghouse steam generators even before the Unit 2 reactor began generating power in 2016 as the last nuclear reactor in the country to be started up by a U.S. utility. TVA paid $160 million for Westinghouse to make the giant 67-foot long, 15-wide steam generators, and TVA has spent millions of dollars more to transport the giant steam generators and store them for the past four years at the Watts Bar site on the Tennessee River near Spring City, Tennessee.

Installing the steam generators also will be another costly investment for TVA during the current refueling outage at the plant. TVA spokesperson Jim Hopson said in a phone interview that utility and contractor employees will have to cut a hole in the top of the containment building to remove the existing steam generators and to replace them with the new units. A giant crane - the second largest mobile crane of its type in the world - will lift the 425-ton replacement steam generators into place.

photo Staff Photo by John Rawlston /A mockup of the control room is seen in the training center at the TVA Watts Bar Nuclear Plant near Spring City, Tenn.

Once the steam generators are replaced and other maintenance work is complete, the nuclear containment building at the Unit 2 reactor will be resealed and air tested to make sure there are no leaks., Hopson said.

Steam generators are used in pressurized water reactors to exchange the heat between the self-contained water circulating in the reactor's primary cooling circuit and a separate supply of water in the secondary circuit that creates steam to spin the turbines and generators to make electricity.

"Investing in this type of extensive plant upgrade doesn't happen often, so our dedicated team has spent years planning every detail to ensure the improvements we are making will help ensure we continue our mission of service to the nearly 10 million people who count on us every day," Watts Bar Site Director Tony Williams said in a statement Thursday as the refueling outage work began. "Watts Bar Unit 2 has consistently produced safe, reliable, low-cost, carbon-free energy for residents and businesses across the region, and the Watts Bar team understands how important it is to maintain that high level of performance."

Prior to being taken offline, the Unit 2 reactor at Watts Bar had produced more than 11.4 billion kilowatt-hours of electricity during its 18-month operation cycle, or enough to supply all of the annual energy needs of 912,000 homes.

With the steam generator replacement, the usual 25- to 35-day outage to install new fuel rods will likely take about twice as long, Hopson said.

In addition to the steam generator replacement project, more than 26,300 work activities are planned. The Watts Bar team will load 88 new nuclear fuel assemblies, perform inspections of reactor components, conduct maintenance of numerous plant equipment and install additional unit enhancements.

The steam generator replacement project at Watts Bar Unit 2 is the last among the four pressurized water reactors that TVA operates. TVA also operates a 3-unit boiling water reactor at Browns Ferry Nuclear Plant in Alabama, but that does not use steam generators.

TVA, the nation's biggest government utility serving nearly 10 million customers, operates the third largest nuclear fleet of any U.S. utility and last year got more than 40% of its power from its seven reactors.

Contact Dave Flessner at dflessner@timesfreepress.com or at 423-757-6340.

photo Staff photo by Tim Barber / Both cooling towers are in operation at Watts Bar Nuclear Plant in this file photo before the Unit 2 reactor was shut down this week for refueling and the installation of four new steam generators.

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