The Department of Energy needs to develop better safeguards to protect workers at the Hanford vitrification plant against a potentially lethal release of ammonia, according to the Defense Nuclear Facilities Safety Board.
The plant, being built by DOE contractor Bechtel National to treat radioactive waste, will include two outdoor tanks holding up to 6,000 gallons each of pressurized liquid anhydrous ammonia. The tanks will be refilled periodically by tanker trucks.
The ammonia will be used as part of a catalytic reduction operation in a system used to control emissions of oxides of nitrogen from waste melters.
DOE has been in ongoing discussions with the defense board about the tanks, which are not under construction yet.
"Safety of the workers, public and environment is always a top priority" for DOE, said Lori Gamache, DOE spokeswoman.
Parts of the plant handling radioactive waste have been designed to withstand a severe earthquake, but the ammonia tanks are not being designed to the same seismic standard, according to the defense board. That decision should be re-evaluated, the defense board said in a letter to DOE.
In the event of a severe earthquake, the tanks could rupture and release a large amount of ammonia. Workers would be evacuated from the plant, potentially exposing them to concentrations of ammonia vapor that could kill multiple workers, the defense board said.
A transportation accident also could expose workers to large, high-concentration plumes, the defense board said. It recommended additional controls, such as more ammonia detectors, personal protection equipment and safe routes for evacuation or locations to shelter in place.
To protect workers in the main control room from a chemical release, a carbon bed has been designed to absorb ammonia before it is drawn into the room's ventilation system.
But the design is insufficient to prevent concentrations from increasing above levels considered immediately dangerous in the control room during a large release of ammonia, the defense board said.
The defense board has requested a report from DOE within 60 days addressing ammonia hazards.
"We are aware of all the items contained in the letter and we are working these items in the course of completing engineering activities," said Suzanne Heaston, spokeswoman for Bechtel National.
-- Annette Cary: 582-1533; firstname.lastname@example.org