The U.S. Nuclear Regulatory Commission (NRC) said Monday it had begun a special inspection of the Grand Gulf Nuclear Station in Port Gibson, Mississippi, to look into operator responses to recent shut downs.
“The purpose of this special inspection is to better understand the circumstances surrounding several recent operational events to determine if operator response was appropriate,” the agency said.
The Grand Gulf plant is a single unit General Electric Type 6 boiling water reactor 20 miles southwest of Vicksburg in Region IV. It has been shut down since Sept. 8.
On Sept. 23, following maintenance on a residual heat removal system, workers discovered that a misalignment of valves had rendered the plant's alternate decay heat removal system unavailable. Technical specifications require that the alternate system be available when one of the plant's two residual heat removal systems is out of service.
The system is used to remove decay heat from the reactor following shutdown.
The following day, when preparing to restart the reactor, control room operators caused an unexpected increase in reactor vessel water level due to a misalignment of valves.
On Sept. 27, Entergy decided the facility would remain shut down until they were satisfied with corrective actions to improve operations, the NRC said.
Three inspectors will spend about a week on site evaluating the operator's root cause analysis and the adequacy of corrective measures. A report on the inspector's findings will be made available to the public within 45 days after completion of the inspectors' review.