By Jean Cole
Terrifying was the televised footage of the tsunami steamrolling across the coast of Japan following a 9.0 earthquake on March 11, 2011.
For those who lived near the Fukushima Daiichi Nuclear Power Plant on Japan’s eastern coast, the days after offered no relief as the plant slouched toward eventual meltdown.
North Alabama residents deal with sometimes-deadly tornadoes on a yearly basis and the occasional, low-magnitude earthquake, but they have never experienced a violent earthquake, a 100-feet tsunami wave or the meltdown of a nuclear plant.
But the disaster at Fukushima, hopefully, will better prepare the Tennessee Valley Authority’s nuclear power plants at Browns Ferry in Athens, and Sequoya and Watts Bar in southeastern Tennessee.
“There were a tremendous number of lessons learned from Fukushima,” said Joey Ledford, Region II spokesman for the Nuclear Regulatory Commission in Atlanta. “Specific upgrades have been ordered for a lot of different plants. All plants had to reassess their ability to withstand a severe natural events, including Browns Ferry.”
The recommendations include requiring plants to have the capability to cope with blackouts of up to 72 hours, backup systems to assure cooling of spent-fuel rods and sufficient margins for beyond-design events involving earthquakes and flooding.
After Fukushima, the NRC learned “Sequoyah and Watts Bar might be subject to flooding due to earthquake but not Browns Ferry because its flood plan proved to be adequate.” Ledford said.
He said the NRC is still waiting for plans to come back with more information on these improvements, such as increasing the height of floodwalls as well as improvements to the facilities.
Ledford also said all nuclear power plants in the United States had to prepare for possible earthquakes before they were built.
Earthquakes rarely work alone. Large ones can bring with them tsunami waves, flooding, landslides, fires, damage to buildings, bridges, dams, highways and other infrastructure, and nuclear accidents.
“Every plant, in the licensing process, has to show a plan for seismic activity as well as flooding,” Ledford said. “It is part of the safety evaluation report and every plant has to do it.”
Officials look at a design’s ability to withstand an historic flood or earthquake. The prospective plant must exceed previously recorded seismic activity in the region, he said. What if the quake exceeds its predecessors?
Although Ledford did not know the precise margin, he said it would be “enough to be safe.”
When a 5.8-magnitude quake struck 11 miles from the North Anna Nuclear Generating Station in Virginia on Aug. 23,2011, the plant automatically shut down as required, he said.
“Because there was enough margin (of safety) in its design phase, it was not damaged,” Ledford said, adding that a spent-nuclear-fuel long-term storage canister shifted during the earthquake. The plant passed inspection and was returned to service.
However, the plant faces additional NRC oversight because a gasket failure, due to improper installation, prevented a diesel generator from performing its function after the quake.