A special investigation is underway into two recent events at the Perry Nuclear Plant near Cleveland, OH, involving a manual shut down on Feb. 8 and a temporary loss of power on Feb. 11, with the reactor shut down.
“On Feb. 8, operators manually shut own the reactor when they observed an increase of the temperature in the suppression pool,” officials at the Nuclear Regulatory Commission (NRC) said Monday.
The suppression pool should condense steam and is a source of water used in emergency cooling systems. The NRC said the Feb. 11 loss of power involved “certain plant cooling equipment.”
Operators were able to use a redundant system and restore power to the cooling systems.
There is no relationship between the Feb. 8 and Feb. 11 events, said NRC Region III Administrator Cynthia Pederson.
Still, “our team of specialists in reactor operations and electrical equipment will review the technical details to better understand what happened,” she said.
Perry, managed by FirstEnergy Nuclear Operating Company, is a 1,260-MW General Electric Type 6 boiling water reactor (BWR) 35 miles northeast of Cleveland that has been in operation since November 1986.
FirstEnergy reported a “spurious” set of signals from pressure and temperature monitors that prompted automated valves in high-pressure steam lines to open. This diverted high-temperature steam on route to the plant’s turbines to a condenser, which allows the steam to cool down and convert back to water.
But the temperature of the condenser suppression pool water was going to rise, which prompted operators to shut down the reactor.
FirstEnergy spokeswoman Jennifer Young said the plant operators reacted “conservatively,” as they should have.
Engineers later said air in the instrument line triggered the steam diversion by giving a false reading of high pressure in the line.
The second shut down came on Feb. 11, when there was a brief electrical shut down to electric pumps that feed coolant water to the reactor. A redundant system activated and plant technicians were looking into the cause of the issue.