The Nuclear Regulatory Commission (NRC) is increasing its oversight of the Watts Bar and Sequoyah nuclear power plants after citing both stations for violations of requirements for analyzing and preparing for potential flooding.
The Tennessee Valley Authority (TVA) operates the The Watts Bar and Sequoyah plants, which are both located on lakes that are part of the Tennessee River system. The location of the plants means both nuclear facilities must each account for potential flooding in their plant design and emergency procedures.
In April, NRC staff held conferences with TVA officials to discuss the risk significance of preliminary inspection findings in the flood protection areas of both nuclear plants.
After reviewing the NRC inspections and information presented by TVA at the conferences, the NRC concluded that the Watts Bar staff would have been unable to implement some of their flood mitigation procedures within the time specified in those procedures. As a result, the NRC concluded that the plant’s flood mitigation strategy had been inadequate until July 2012 when the plant took compensatory measures. The NRC staff has classified that violation as yellow, meaning it has substantial safety significance.
NRC staff also concluded the TVA did not establish adequate flood protection for the potential failure of upstream dams at its Sequoyah plant and has classified that violation as white, meaning it has low to moderate safety significance
The NRC also found that TVA had not taken necessary measures at Sequoyah to prevent water from entering the intake pumping station in the event of flooding. The NRC has also classified that violation as white.
Both Watts Bar and Sequoyah were also cited for a violation because TVA did not notify the NRC within eight hours after discovery that the potential failure of the upstream dams and subsequent potential onsite flooding resulted in an unanalyzed condition affecting safety at both facilities.
The NRC will schedule inspections to evaluate TVA’s corrective actions for the yellow and white issues, and TVA must respond in writing with their corrective actions for the reporting violations.
No actual flooding event that would have affected either plant’s safety equipment has occurred.