NASHVILLE — The Nuclear Regulatory Commission has told the Tennessee Valley Authority that sand baskets installed at four TVA dams to protect downstream nuclear facilities from flooding are acceptable temporarily but not as a long-term solution.
The NRC letter obtained by The Tennessean said the baskets might not withstand the impact of large debris in a potential flood overflow that a TVA spokesman described Thursday as “the flood event that we have never ever seen before.”
“There is potential for this debris to damage the baskets or push the individual baskets apart, causing a breach,” the NRC’s Wednesday letter says. “There would be no time to repair the baskets because the flood would already be in progress.
“Therefore, sand baskets that are not designed and constructed to withstand impacts from large debris are not acceptable as a long-term solution.”
NRC spokesman Roger Hannah said the sand-filled, wire mesh baskets placed around Cherokee, Fort Loudoun, Tellico and Watts Bar dams and earthen embankments, are related to flood studies and TVA’s planned Bellefonte reactor in Northeast Alabama.
TVA spokesman Travis Brickey said possible long-term alternatives include extending the tops of dams with concrete.
“We are doing an environmental study on what the permanent” alternative will be, Brickey said.
TVA had told the NRC in 2010 that a project to resolve flooding concerns would extend into 2016, with dam modifications handled by the U.S. Army Corps of Engineers.
The NRC said the baskets will have to do for now but requested that TVA provide a status update at least once a year on its work.
“It’s acceptable as a temporary fix,” NRC Atlanta-region spokesman Joey Ledford said.
Ledford said it’s TVA’s Sequoyah Nuclear Plant near Chattanooga “that might have the most problems” in the event of such a flood catastrophe.
“We believe the plant is safe,” TVA nuclear spokesman Ray Golden said. “If there is an opportunity to make it safer, we will pursue it.”
At Sequoyah, diesel generators and spent fuel pool cooling pumps could be affected, the NRC letter said. Having backup power and keeping highly radioactive waste cool at plants are critical and were a major factor in the disaster last year after an earthquake and tsunami at the Fukushima nuclear complex in Japan.
TVA provides electricity to about 9 million consumers in parts of Tennessee, Kentucky, Alabama, Georgia, North Carolina, Virginia and Mississippi.