One of the three units at Browns Ferry Nuclear Plant near Huntsville has been shut down for scheduled maintenance as part of a $475 million upgrade at the Limestone County facility.

TVA announced Monday that Unit 1 at Browns Ferry started a refueling and maintenance outage on Sunday. The federally-owned utility is using the outage as an opportunity to bring it up to the level of Extended Power Uprate.

Once the EPU is in place on all three units, Browns Ferry will generate an additional 465 megawatts, which TVA said was enough to power an additional 280,000 homes.

"There is added importance to this and our next outage because we will complete the remaining work needed to operate each unit at Extended Power Uprate conditions to serve the energy needs of the Tennessee Valley," Lang Hughes, Browns Ferry site vice president, said in the announcement.

During this outage, TVA said it will install 332 new nuclear fuel assemblies and perform a final round of EPU modifications to prepare Unit 1 to become the second of the three Browns Ferry units to generate an additional 155 megawatts of electricity - up to 1,311 megawatts of electricity total for Unit 1. In July, Unit 3 began operating at the new EPU power rating and final EPU modifications will be installed on Unit 2 next spring.

Once all three units are operating at EPU power levels, Browns Ferry will generate up to 3,933 megawatts of carbon-free electricity total. TVA said the improvements will help fulfill its mission of service for decades to come by delivering more low-cost and cleaner energy to the people of the Tennessee Valley, which helps keep rates stable and fosters economic development.

"Outages are our best opportunity to do the necessary work that prepares the unit to safely and reliably generate carbon-free electricity for the next two years," Hughes said in the announcement.

Browns Ferry's regular staff will be supplemented by more than 2,000 additional TVA and contract employees during the outage.

More than 14,700 work activities are scheduled, including maintenance and upgrades of plant equipment, inspections and repairs on reactor components and installing modifications to improve safety margins. TVA's seven operational nuclear reactors supply about 40 percent of all electricity used by nearly 10 million people in the Tennessee Valley.