The Hanford C Tank Farm was evacuated Tuesday when smoke was seen near an exhauster about 3 p.m.
Chemical vapors vented from underground tanks holding radioactive waste go into exhausters to help filters keep particulates from the tanks from being vented into the air.
The Hanford Fire Department responded, initially using cameras installed in the area to monitor the situation and then entering the tank farm about 3:45 p.m. There was no evidence of flames and no more smoke was seen, said Rob Roxburgh, spokesman for Washington River Protection Solutions.
A survey found no release of radioactive contamination, he said.
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The exhauster has been secured to prevent it from operating and troubleshooting is planned for this morning. Workers were allowed back into the tank farm, which has 16 underground tanks, about 5 p.m, Roxburgh said.