When a series of strong tornadoes swept through the Tennessee Valley in late April, the Browns Ferry nuclear energy facility was ready for nature’s challenge. Dozens of tornadoes, including four EF5 storms—the strongest on the scale used by the National Weather Service—battered the Southeast and the Tennessee Valley Authority’s transmission system, severing power lines to Browns Ferry.
The tornadoes destroyed 353 of TVA’s transmission poles and towers and took out 108 power lines, including the seven transmission lines that serve as the Athens, Ala., site’s primary source of power.
When all but one power line to the plant went out of service, operators guided the safe shutdown of the facility’s three reactors. Seven emergency diesel generators provided power to safety systems that kept the reactor fuel cores cooled.
As bad as the storms were, Browns Ferry was designed to withstand far worse. In fact, every U.S. nuclear energy facility is built to withstand floods, earthquakes and tornados worse than any on record for its area. In the event of a catastrophic event, safety systems are designed to keep reactors in safe shutdown mode, with the fuel cores cooled.
Browns Ferry’s response planning and procedures allowed the plant to be fully prepared when the tornadoes passed through the area.
On a typical day, producing electric power safely and efficiently for about 2.6 million homes and businesses takes precedence for Keith Polson, Browns Ferry’s site vice president. During the tornado outbreak, however, he first turned his focus to ensuring the safety of his employees.
“When there was a threat of a tornado close to the plant, we entered our severe weather procedure,” said Keith Polson, Browns Ferry’s site vice president. “Our first concern is the people at the site, making sure they’re safe. We made sure people got inside the plant, where it’s most secure.”
An equally high priority ensuring the reactors and spent fuel storage pools remained safely cooled to protect the health and safety of the public. Another priority was maintaining operation of the plant’s seven diesel generators, which provided backup power to the facility and cooled the three reactors for five days after the storm.
Polson emphasized that the facility’s culture of safety, which includes frequent safety training drills, prepared the Browns Ferry staff for the event.
“We were fully prepared for what happened, losing [power to] all three reactors. It’s all the training that the operators do. Every six weeks they have one week of training,” he said.
Browns Ferry set up an operational response center to coordinate its response to the storms, supported by TVA’s corporate offices in Chattanooga, Tenn. The center was staffed by experts in engineering, operations, emergency response and other relevant disciplines, and knowledge was shared across all fields to ensure the best results.
Within 15 minutes of losing power to all three units, TVA notified state officials, in accordance with the company’s procedures and the requirements of the independent Nuclear Regulatory Commission, the federal agency charged with oversight of the nuclear power industry. The NRC’s chief resident inspector at Browns Ferry reported to the facility’s control room within minutes of the power loss and served as a liaison to the commission’s regional office in Atlanta throughout the storm.
Browns Ferry’s staff regularly reviews the facility’s equipment and emergency response procedures, drawing from experience at the site and lessons learned by the nuclear energy industry as a whole, to identify ways to make the plant even safer.
Polson said the facility’s management also will incorporate lessons from the Fukushima Daiichi accident in Japan into its planning.
“I think that both our experience and the Fukushima experience caused us to take a look at highly unusual scenarios… to further enhance our training and our safety equipment,” he said. “These plants are robustly designed to withstand earthquakes, floods and tornadoes beyond what the historic records indicate for the Tennessee Valley.”