Operators aborted a reactor restart at the Susquehanna nuclear plant last week after a problem with the unit's turbine bypass valves, according to a report filed with regulators.
Unit 1 had reached 7 percent power just after noon Friday when all of the turbine bypass valves opened unexpectedly, according to the Nuclear Regulatory Commission. A report released Monday noted the "reactor feed pumps, main turbine, HPCI (high-pressure coolant injection system) and RCIC (reactor core isolation cooling system) tripped on the high level setpoint Level 8 (+54 inches) due to the resultant reactor level swell."
The event did not trigger the automatic emergency core cooling system, and all safety systems functioned as designed during the manual shutdown. While plant owner PPL did not issue a statement on the trip, a daily NRC status report indicated the reactor was back at 3 percent power on Monday.
The boiling water reactor had shut down May 9 for a scheduled refueling and maintenance outage. According to a PPL release, more than 1,000 supplemental workers also performed extensive testing, inspections and upgrades. These included replacement of a 24-ton coolant pump and improvements to address turbine blades that have caused problems at the plant in the past.