Tennesee Valley Authority Pressed for Details on Nuclear Plant Flood Safety

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Nuclear power plant regulators want more specific information from Tennessee Valley Authority (TVA) on how the utility plans to protect reactors in case of severe flooding.

According to the Chattanooga Times Free Press, the Nuclear Regulatory Commission heard TVA’s flood plans earlier this week and scheduled another meeting on Dec. 13, seeking more information.

An NRC project manager at the meeting in Atlanta asked why the Watts Bar Nuclear Plant at Spring City, Tenn., should be allowed to continue operating, saying a ring of temporary crushed stone baskets has gaps.

TVA Vice President Dan Jernigan said the utility has a plan to fill the gaps where roads run into the plant in case of severe flooding.

Using newer technology and information, TVA concluded a catastrophic flood could inundate critical reactor control equipment.

TVA discovered the need while planning for resumption of construction at the Bellefont Nuclear Plant near Scottsboro, Ala. New calculations showed a “probable maximum flood” would cause water to rise 4 feet higher than the Watts Bar Nuclear Plant was designed and licensed to withstand. Such a flood could bring water nearly two and a half feet deeper than the Sequoyah Nuclear Plant at Soddy-Daisy, Tenn., was designed for.

By TVA’s estimate, a maximum flood scenario would begin with more than 6 inches of rain falling across the 20,000 square miles of the East Tennessee watershed. Then, an additional 16-17 inches of rainfall in the next six days on already-saturated soil would trigger such a flood.

Jernigan told regulators that modifications are under way at both plants — both inside the plants and along the sides of four dams in East Tennessee — Fort Loudon, Tellico, Cherokee and Watts Bar.

Officials from both Watts Bar and Sequoyah told the NRC that sealing around doors and conduits is being upgraded.

At the mid-December meeting, TVA will give the regulators specifics about when, in the event of severe flooding, the gaps in the crushed stone baskets surrounding the Watts Bar plant would be filled. The federal utility will also answer questions about how the temporary wall would withstand a strike by a barge during flooding.

“Our analysis shows (the barriers) would hold,” Jernigan said.