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.
The Hanford Patrol established a 100-foot isolation zone around the area of the leak and planned to monitor it remotely through the night. Additional actions will be considered in the morning.
The 200 East Area and the 200 West Area are in the 75-square-mile plateau in the center of the 580-square-mile site and have underground tanks holding a total of 56 million gallons of radioactive and hazardous chemical waste.
The waste is left from the past production of plutonium from World War II through the Cold War for the nation’s nuclear weapons program.
The 200 East Area also has the vitrification plant, which is being built and commissioned to treat the tank waste for disposal.
The parts of the plant that will treat the least radioactive of the waste are currently being commissioned and no radioactive waste will be brought into the plant until next year.
About 75 workers were at the vitrification plant, formally called the Waste Treatment Plant, late Friday afternoon on shifts scheduled to end at 6:30 p.m.
The number of workers at the 200 East tank farms was not immediately available, but numbers likely would have been low since most employees there work 10-hour shifts Monday through Thursday.
When the vitrification plant is treating waste, it will release oxides of nitrogen into the Low Activity Waste Facility’s exhaust system.
Ammonia is used to cause a chemical reaction that significantly reduces the level of oxides of nitrogen to meet air permit levels.
The plant has two tanks, each approximately 24 feet long and 7 feet in diameter, with a capacity of 6,000 gallons of liquid ammonia each.
The tank had been charged, but held only ammonia vapors.
When waste treatment begins, about 7,600 gallons of ammonia will be stored at the vitrification plant at any given time and about 6,000 gallons of ammonia will be used per month.
The vitrification plant’s chemical safety management program identifies anhydrous ammonia as a potential hazard.
Ammonia can cause chemical burns upon skin contact and lung damage if inhaled in large quantities.
Additionally, it is a cryogenic hazard, meaning it can cause clothing to freeze and stick to the skin of the person exposed, according to Bechtel National, the Department of Energy contractor building and commissioning the plant.
Ammonia is a colorless gas with a distinct, pungent odor and is widely used in agriculture as fertilizer, in household and industrial cleaning products, in refrigeration systems, and in the production of plastics and textiles.
