The Nuclear Regulatory Commission has sent an Augmented Inspection Team (AIT) to the River Bend nuclear power plant to review the circumstances surrounding a shutdown of the reactor caused by an electrical switchgear malfunction on May 24. The plant, operated by Entergy Operations, is located in St. Francisville, La.
Shortly before 2 p.m. on May 24 operators manually shut down the reactor after an electrical fault occurred in a main feedwater pump. The plant was operating at 33 percent power at the time. Protective relays should have isolated the electrical fault. Instead, in a cascading effect, other pieces of equipment were affected, causing a loss of main feedwater to the reactor core.
The plant’s Reactor Core Cooling Isolation System activated as designed to provide cooling to the reactor core. Plant personnel are continuing to investigate the cause of the failure and determine necessary repairs. Workers reported seeing some smoke around the reactor feed pump and the plant’s fire brigade was dispatched, but no fire was reported.
The plant is in safe shutdown condition. No emergency action level declaration was necessary, and there were no radiological releases as a result of the event.
NRC resident inspectors responded to the control room to monitor site activities during the event and were onsite during the weekend to monitor licensee activities and initial recovery actions.
AIT’s are used by the NRC to review more significant events or issues at NRC-licensed facilities. The four-member team has assumed responsibility from the resident inspectors for gathering information about the shutdown event. The team leader arrived on site Saturday; other members are expected later today. The team is expected to remain on site through June 8.
The team includes fire protection and operations specialists from the NRC’s Region IV office. The team is led by NRC Region IV Branch Chief Geoffrey Miller of the Division of Reactor Safety.
“An AIT is used when the NRC wants to promptly dig deeply into the circumstances surrounding an operational event,” said NRC Region IV Administrator Elmo E. Collins. “We want to make sure that all of the circumstances that contributed to this event are well understood in order to prevent a recurrence.”
The team will put together a detailed chronology of the event, evaluate the adequacy of licensee actions in response to the incident and assess the impact of the prolonged loss of off-site power to non-safety related equipment. The team’s report will not contain inspection findings, but will identify areas for further inspection follow-up.
The NRC will hold a public exit meeting with the licensee upon completion of the inspection to discuss its preliminary findings. The meeting will be open to interested members of the public and the news media, and team members will be available to answer questions after the results are presented. The AIT will also issue a written report within 30 days of completion of the inspection.