In the ten years since the March 2011 Fukushima disaster in Japan, the U.S. nuclear energy industry has added safety and protective measures to prevent a similar incident at a U.S. facility. As a nuclear industry leader, TVA’s three nuclear plants were among the first to fully implement an entirely new layer of protection against the most extreme natural events.
Within days of the earthquake and tsunami that overwhelmed the Fukushima plant, U.S. President Barack Obama ordered all U.S. nuclear facilities to conduct a comprehensive review of safety equipment and procedures. The Nuclear Regulatory Commission also carefully analyzed the event in Japan and issued a series of new requirements that all U.S. facilities must meet.
Individuals touring one of Watts Bar’s four diesel generators, capable of supplying all of the power needed to run key safety and cooling systems at the plant.
The most important lesson of the accident in Japan is to ensure all nuclear plants worldwide can handle catastrophic natural events, regardless of the cause, even if such an occurrence would go beyond the plant design. Specifically, nuclear plants must be prepared to sustain loss of external power and maintain the ability to cool the reactor, spent fuel pool and containment.
At TVA, the Watts Bar Unit 2 completion project provided the unique opportunity to fully examine the potential impacts of extreme flooding and other extreme natural conditions on a facility that was still under construction. The additional resources already onsite were able to incorporate the Fukushima lessons learned directly into the new unit, which successfully became the first nuclear generation unit to come online in the 21st century.
Led by the Nuclear Energy Institute, TVA and the U.S. nuclear industry developed a diverse and flexible approach called the FLEX program that adds to the already robust safety systems at each plant. On top of the multiple redundant systems, such as backup power and water supplies, U.S. nuclear power plants added another layer of assurance with the FLEX program.
Numerous portable pumps, generators and other equipment are stored in the hardened FLEX and can be instantly deployed if needed for extreme events.
Building on existing installed backup safety systems, this strategy addresses the major problem encountered at Fukushima—the loss of power to maintain effective reactor cooling—by stationing another layer of backup equipment at facility sites. In addition, the industry opened national rapid response centers in Phoenix, Ariz., and Memphis, Tenn., with additional equipment stored that could be flown quickly to any domestic plant site, if necessary.
TVA’s Watts Bar nuclear plant was the first plant to meet the additional requirements following the Fukushima incident, including installing and positioning FLEX program equipment in a new dedicated building, hardened to withstand extreme natural events. This includes portable equipment, such as generators and pumps, that could keep the reactor and used fuel pool cool if the usual systems are not available.
Overall, TVA invested $180 million in modifications to the Browns Ferry, Sequoyah and Watts Bar plants in response to Fukushima, including performing additional seismic and hydrology studies.
A decade after the Fukushima incident, TVA and the entire U.S. nuclear industry is still learning from this and other extreme weather events that go beyond original plant design conditions. Teams around the country continue to conduct analysis and drills, and share the experience across the industry, to ensure nothing like Fukushima occurs in the United States or elsewhere.
Exterior of the Watts Bar FLEX Building
Individuals touring one of Watts Bar’s four diesel generators, capable of supplying all of the power needed to run key safety and cooling systems at the plant
Numerous portable pumps, generators and other equipment are stored in the hardened FLEX and can be instantly deployed if needed for extreme events