SODDY-DAISY, TN (WRCB) -- The Nuclear Regulatory Commission issued an inspection report and follow-up assessment letter on March 29, notifying the Tennessee Valley Authority that the Sequoyah Nuclear Plant had successfully improved its performance to allow for fewer inspections during the year.

The NRC acknowledged that the performance indicator related to unplanned reactor shutdowns had reverted back to "green" from the "white" color designation.    

"Our team has worked very hard to make equipment upgrades to ensure that our plant continues to operate reliably and safely," said John Carlin, Sequoyah site vice president. "This successful inspection proves that we understand the equipment challenges that led to our unplanned shutdowns, and have identified the corrective actions to prevent them from happening again. Our No. 1 priority in everything we do is protecting the health and safety of the public and our employees."

In March, as a result of the white performance indicator, the NRC performed a supplemental inspection at Sequoyah to determine if the site understood the causes of the unplanned reactor shutdowns, and to ensure that the corrective actions were sufficiently developed to prevent further events.

The NRC determined that the Sequoyah team understood the causes and that sufficient corrective actions were in place to address and eliminate those issues. In addition, the report noted that no significant weaknesses have been identified, and Sequoyah's problem identification, root cause analysis and corrective actions were adequate.

From the fall of 2010 to summer 2011, Sequoyah Unit 1 had five unplanned shutdowns within 7,000 operating hours, leading to a white performance indicator. This placed Sequoyah into the NRC's increased regulatory oversight process.  

The NRC uses a color-coded risk assessment process to determine if it should provide greater regulatory oversight and inspections. Green indicates an expected performance level, white signifies performance outside the expected range of nominal utility performance, yellow indicates operational objectives are met with minimal reduction in safety margin and a red indicator means there is a significant reduction in safety margin in the area measured.  

The Sequoyah team worked to reduce the possibility of equipment or work processes causing a shutdown or a single point of failure, where one unintentional action can shut the plant down.

"At Sequoyah we continually work to improve our processes to ensure we reliably provide power to the TVA system," Carlin said.