KENNEWICK -- Workers in part of the center of the Hanford nuclear site were ordered to take cover indoors at 4:50 p.m. Friday.
A large holding tank with ammonia vapor was discovered by workers to be leaking near the vitrification plant in the 200 East Area, according to the Hanford Emergency Operations Center.
The tank's valves were closed when the leak was detected.
Workers in that area were told to go indoors and shelter in place with doors, windows and ventilation closed until the take cover was lifted at about 6:40 p.m.
Other workers at the site were told to avoid the 200 East Area, which is about seven miles from the Columbia River and 22 miles north of Richland.