From staff, wire reports
A reactor at Browns Ferry Nuclear Plant reached full power Thursday, five days after an unexpected shutdown.
The Unit 2 reactor shut down at 2 p.m. on Saturday when a faulty electrical cable interrupted power to plant equipment, triggering the reactor trip, or “scram.”
The unit came back online Wednesday, and was synchronized to TVA’s power grid at 2 p.m., according to TVA spokesman Ray Golden. By Thursday afternoon, power had returned to 100 percent.
Following the shutdown, resident inspectors with the U.S. Nuclear Regulatory Commission responded, according to NRC spokesman Joey Ledford. Part of that response, he said, was to monitor plant activities and to ensure the plant was in a safe condition.
“(Inspectors) monitored the restart on Dec. 26, and we will continue to analyze their actions as to what caused this scram,” he said.
Ledford added that there’s nothing overly worrisome about an unplanned scram, but plant licensees are required to report each outage.
Browns Ferry Nuclear Plant has been under increased NRC scrutiny following the failure of a residual heat removal valve on the Unit 1 redundant fire protection system in late 2010.
The finding placed Unit 1 in the NRC’s repetitive degraded cornerstone column, and kicked off an intensive three-part inspection, known in the industry as a 95003 inspection. The final part of that inspection could begin in early 2013.
At a public meeting held earlier this month, the NRC announced it had completed three inspections following a white inspection finding and two white performance indicators.
One inspection was related to a white (low-to-moderate safety risk) finding issued in response to plant operators not being aware of new safe shutdown procedures. The two other inspections looked at the response to a white performance indicator caused by Unit 1’s high-pressure injection system being out of service more than expected and a white performance indicator related to unplanned shutdowns on Unit 3.
When asked if the most recent shutdown at Browns Ferry would require additional NRC oversight, Ledford said there would have to be “a number” of scrams that occur within a period of 7,000 operating hours for each unit.
“Three or more can end up bumping them into the next regulatory category,” he said. “Obviously, (the NRC’s) primary focus has been on Unit 1. But the (inspection) focus is already there, so we’ll closely monitor all activities.”
The Unit 2 shutdown occurred after establishing a record run of 562 days of continuous operation. Golden said Unit 2 is capable of providing low-cost, clean power to 650,000 homes and businesses, while all three produce enough power for 2 million people.
“The record run demonstrates the ongoing commitment of TVA and its Browns Ferry employees have regarding sustained operational excellence and improved equipment reliability,” he said.