A special inspection is underway at the nuclear power plant near Richland, WA, after lack of maintenance caused a problem with a cooling system, federal regulators said.
A large heat exchanger that cools a room housing electrical circuit breakers and batteries to provide direct current to switches and alarms was not working to full capacity, which could be an issue in an emergency at Energy Northwest’s Columbia Generating Station, said officials at the Nuclear Regulatory Commission (NRC).
However, a separate backup system was available to provide cooling in case of an emergency.
There was no question or concern about the cooling system being able to keep the room cool during normal operations, said Don Gregoire, Energy Northwest manager of regulatory affairs. They were monitoring the temperature in the room and had it become warm, an alarm would have sounded well before the room was hot enough to cause a problem, according to Energy Northwest.
The problem first came to light during the refueling outage at the nuclear power plant this spring as an engineer was checking the inside of the cooling coils and decided to take a look at the side of the cooling coils where the problem was discovered, Gregoire said. Dust and material from the air filters was on the coils, reducing the system’s capacity to cool.
A maintenance plan had considered inspections of that part of the system optional because past experience found very little problem with it, Gregoire said. It had not undergone inspection in six years.
They immediately cleaned the system and maintenance is now mandatory, he said.
Energy Northwest also looked at similar cooling systems at the nuclear plant and found no additional problems.
Because more heat could end up generated in an emergency, testing is ongoing to evaluate how much cooling capacity was lost before they discovered the issue, Gregoire said.
“The purpose of this special inspection is to better understand the sequence of events that contributed to the maintenance problem and review the licensee’s corrective actions,” said Arthur Howell, NRC Region IV administrator.
A “special investigation” is the lowest level of investigation performed by the NRC in response to an issue, according to Energy Northwest.
The investigation will take about a week and findings should be available within 45 days of its completion.