BOISE – All 16 workers exposed to radiation at the Idaho National Laboratory were allowed to go home following the incident, which officials Wednesday said likely resulted from decades-old plutonium powder that escaped its damaged stainless-steel shell.
After a follow-up lung scan Wednesday, one worker still tested positive for radioactive material in the lungs and was receiving extra attention at the lab’s medical facility. Seven of the employees tested positive for external skin contamination, and six had positive nasal swipes.
All 16 workers will undergo weeks of testing, including urine analysis, to evaluate their level of exposure. Plutonium, if it remains in the body, can cause cell damage.
Lab health director Sharon Dossett said none of the exposed workers was exhibiting outward symptoms of radiological exposure. They were allowed to go home because they posed no threat to others, she said.
“These isotopes are internal hazards; they’re not external hazards,” Dossett told reporters at a news conference Wednesday. “There’s no hazard to their family members or anybody they would come into contact with.”
INL officials declined to provide details about the workers.
The lone employee who tested positive for radioactive material in the lungs Wednesday had breathed in Americium-241, an isotope commonly found in nuclear waste. While the lung scans aren’t sensitive enough to detect plutonium, the presence of Americium-241 proves plutonium is there, too.
“It’s for sure,” Dossett said.
According to lab officials, it may be weeks before the extent of all the workers’ exposure is known.
Idaho National Laboratory officials said filters meant to keep radioactive material from being released from exhaust systems inside the facility functioned properly. There was no risk to the public or the environment, the laboratory said in a statement.
Early Tuesday afternoon, workers were recovering the fuel so it could be shipped to a U.S. Department of Energy facility in an undisclosed state.
Lab officials suspect the stainless steel cladding that surrounded the plutonium was damaged years ago, beginning a slow-but-steady process of plutonium oxidation that led to the exposure. When workers opened an aluminum box that housed the fuel plates and cut away plastic wrapping, they noticed several grains of powder that escaped.