Browns Ferry Nuclear Plant is seeing white for not following procedures while restoring power at its Unit 2 reactor protection system.
A Dec. 22, 2012, failure caused the reactor to shut down after the protection system lost both primary power supplies and the main steam isolation valves closed. The main steam isolation valves should close in the event of a rupture in the plant’s steam pipes, said officials at the Nuclear Regulatory Commission, which cited the Tennessee Valley Authority (TVA) with a white finding.
The first power supply de-energized during post-maintenance testing of an emergency diesel generator.
While attempting to re-energize the reactor protection system’s power supply, a licensed operator “inadvertently” de-energized the second RPS power supply, the TVA said.
The NRC said it determined TVA’s inspection finding at the plant “has low to moderate safety significance.”
TVA spokesman Scott Brooks said the utility accepts the NRC’s finding.
Brooks said TVA has developed corrective actions to prevent a recurrence. In addition, the utility “compared these issues to broader actions developed for the NRC’s recently completed 95003 inspection” to ensure they are part of the power station’s improvement plan.
The event was part of the discussion during an NRC regulatory conference July 24. After considering the NRC analysis as well as information presented by TVA at the conference, the NRC concluded they should classify the failure by a TVA operator to follow procedures as white, or having low-to-moderate safety significance.
Since Browns Ferry’s Unit 2 is already under increased NRC oversight, the finding will not change the level of oversight. However, the agency will conduct a supplemental inspection to ensure TVA understands the cause and extent of the issue and has taken appropriate corrective actions.
The NRC sent a letter to TVA with the final significance determination and notice of violation.