A small fire broke out about 3 p.m. Friday in a ventilation system of the Areva plant in Richland, which manufactures fuel assemblies for nuclear power reactors.
No radioactive material is believed to have been involved, said Tom Huntington, a Richland Fire Department battalion chief.
There also were no contaminants released from the plant, according to Areva.
The fire was in the uranium oxide building, where uranium is manufactured into fuel pellets for reactor fuel assemblies, but was in a small back room used to cut metal, said Areva spokeswoman Anna Markham.
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The ventilation system there is part of a system that is self-contained, with no air blowing outside, she said. Air samples taken in the room showed no abnormal conditions, she said.
Richland firefighters received an alarm from the building and followed procedures they practice frequently in drills with Areva, Huntington said.
Areva workers who would check for contaminants met firefighters at the gate and entered the building with them within a minute and a half, he said. The concern for a radioactive release was very low as firefighters went in, he said.
Firefighters discovered a series of small fires in the ventilation system that were difficult to access, he said. Because they had to tear apart enough of the system to reach the fires, it took until 4:05 p.m. to extinguish them, he said.
Thermal cameras were used to check for hot spots in the ventilation system.
Crews from the Hanford Fire Department and Benton Fire District 4 also responded, and crews from Kennewick and Pasco were on the way when they were told they could turn around.
Employees in the building evacuated and none were affected, Markham said. About 350 workers were at the plant Friday afternoon.
Areva declared an alert, which still was in place at 8 p.m. Friday, and notified the Nuclear Regulatory Commission; state agencies, including the Department of Health, and county agencies.
Fire crews left Areva, which is on Horn Rapids Road, about 6:30 p.m., and an investigation into the cause of the fire is continuing, Huntington said.
"We have a very, very solid relationship with Areva," Huntington said. "They train regularly. They do a good job."