The nuclear power plant near Richland had its first scram, or unplanned shutdown, in more than six years Monday afternoon.
About 1:30 p.m. the Columbia Generating Station’s control room received an indication that a system used to cool equipment was not operable, said Mike Paoli, Energy Northwest spokesman.
The system uses water to provide cooling to pumps and heat exchangers in the plant, including the pumps used to recirculate the water used to control the power level of the reactor.
Operators shut down the plant.
Preliminary indications are that the issue was with a water system valve that was not in the appropriate position, Paoli said. Although the investigation is just beginning, human error may be a reasonable cause to explore, he said.
A decision on restarting the plant will be made after a thorough review of the event and when operators have confidence that all systems can operate to standards, he said. The decision might be made within the next few days.
“Scrams are not unusual events in the industry, but they are not what we like to see to meet our generation numbers,” Paoli said.
The nation has 99 operating nuclear reactors and collectively they had more than 110 scrams in the last two years, he said.
The plant broke generation records in December and January, operating in January above its peak capacity factor, which is set at the maximum amount of electricity the plant can send to the grid in the summer. It produces enough electricity to power a city about the size of Seattle.
It also had set a new record for the longest continuous operational run last year, operating for 683 days before shutting down for a planned biennial refueling and maintenance outage.
The last scram at the Columbia Generating Station was in November 2009, when hydraulic fluid was found leaking from an O-ring. The leak affected the plant’s main turbine, requiring it to be taken offline so repairs could be made.
The scram ended a string of six scrams starting in August 2008 that caused the Nuclear Regulatory Commission to increase oversight in 2010, but the plant was back to normal oversight the next year. The last NRC annual review found the plant operated safely in 2015.