Workers at the Hanford Site’s Plutonium Finishing Plant were ordered to take cover indoors for more than three hours Thursday morning as a precaution after an air monitor detected low levels of airborne contamination, according to the Department of Energy.
A survey subsequently found spots of radioactive contamination had spread outside the demolition zone established at the plant. Low-level contamination was found on sidewalks, near a station where employees pick up respirators, and near a vehicle access gate.
No employee was injured and no skin contamination was found. There also was no indication of internal contamination to personnel, said Destry Henderson, spokesman for Plutonium Finishing Plant demolition contractor CH2M Hill Plateau Remediation Co.
The air monitor signaled an alarm during open-air demolition at the plant. The plant’s Plutonium Reclamation Facility had been demolished enough to expose the glove boxes that run the length of both sides of the facility’s central canyon. Workers were using a shear on the end of an excavator arm to peel off the front face of one of four glove boxes running the length of the canyon. The incorporation of the glove boxes in the shuttered facility means they cannot be removed intact as many smaller glove boxes at the plant have been.
Workers immediately stopped demolition when the air monitor alarm sounded; they then sprayed fixative in the area to glue any loose contamination in place, DOE said in a statement. The take-cover order was issued within minutes at 6:58 a.m. When initial surveys showed no danger to workers, the order was lifted about 10:45 a.m. Fixative had been sprayed on contamination found on the sidewalk and elsewhere, and workers were told to avoid those areas. The contamination was planned to be removed and disposed of, as surveying and other recovery work continued into Thursday evening.
“Air monitoring alarms during demolition are not unexpected,” DOE said. “This is one of the monitoring tools used to ensure demolition of the plant proceeds safely.” As open-air demolition is done, water is sprayed to control dust and fixative is sprayed to control any loose contamination, turning most of the demolition area a bright blue.
A take-cover order was issued at the Plutonium Finishing Plant on Jan. 27 when radioactive contamination spread as debris from demolition of the Plutonium Reclamation Facility was moved. Because it was late in the afternoon on a Friday, a day off for those employees who work four 10-hour shifts a week, the number of workers at the plant was limited. No internal or skin contamination was found on workers in the January incident.
The Plutonium Reclamation Facility was added at one end of the main Plutonium Finishing Plant processing area to recover plutonium from scrap as a way to ramp up plutonium production for nuclear weapons during the Cold War. The facility was connected to the main processing plant by the McCluskey Room, which has been torn down to slab on grade. The work schedule calls for the Plutonium Reclamation Facility to be demolished in July as DOE works to meet a September deadline to have the entire plant to slab on grade.
The PFP canyon is the most contaminated area of the plant. It is 34 feet tall and has a footprint of 30 feet by 66 feet. Skinny tanks, called pencil tanks, were hung along its walls to separate plutonium from scrap material. The gallery glove boxes that line the canyon at ground level and a level above that had equipment removed, along with as much contamination as possible, before demolition of the Plutonium Reclamation Facility began in November.
“Open air demolition is challenging,” Henderson said. “That’s why we spent years preparing for demolition and have robust mitigation and monitoring in place.”
