In a Wednesday, Oct. 19, 2011, file photo, Walter Lee, right, manager of Nuclear Emergency Preparedness, leads the evaluation as the Tennessee Valley Authority conducts an emergency preparedness drill in the Central Emergency Control Center in Chattanooga, Tenn. (AP Photo/Chattanooga Times Free Press, Dan Henry)** FILE **

Photo by: Dan Henry

In a Wednesday, Oct. 19, 2011, file photo, Walter Lee, right, manager of Nuclear Emergency Preparedness, leads the evaluation as the Tennessee Valley Authority conducts an emergency preparedness drill in the Central Emergency Control Center in Chattanooga, Tenn. (AP Photo/Chattanooga Times Free Press, Dan Henry)** FILE **