After completing a refueling outage and restarting the newest reactor at the Sequoyah Nuclear Power Plant last week, the Tennessee Valley Authority let off some steam early Wednesday at the other Sequoyah unit, waking up some residents who heard the loud noise around 2 a.m.
The noise stemmed from the sudden release of steam from the turbine on the non-nuclear part of the Unit 1 reactor at Sequoyah when a problem in the turbine forced the reactor to trip on the non-nuclear side of the power plant.
In a report on the incident, the U.S. Nuclear Regulatory Commission said a low steam line pressure safety injection signal was actuated and the reactor tripped when there was a drop in the steam pressure rate in the turbine building.
"Main steam isolation valves automatically closed as designed and steam generator pressures stabilized following the isolation," the NRC said in a report on the incident.
TVA spokeswoman Malinda Hunter said the Unit 1 reactor "was safely shut down and there are no impacts to the safety of employees or the public."
"Reactor safety systems performed as designed, operators took appropriate actions and the plant is stable while teams evaluate the issue," she said.
TVA said once the turbine problem is assessed, fixed and tested, the unit 1 reactor will begin ascending power again to return to full operation.
The Unit 2 reactor at Sequoyah, which was restarted last week following a 23-day outage, is operating safely at 100% power, Hunter said.
TVA began a refueling of the Unit 1 reactor at the Watts Bar plant last weekend.