Two Hanford Plutonium Finishing Plant workers have very low levels of radioactive contamination in their bodies after an incident in early January, an investigation concluded.
One worker will receive 3 millirems of radiation throughout 50 years from material he likely breathed in and the other will receive 1 millirem, according to estimates developed with bioassays.
The Department of Energy limit is 500 millirems per year, said Dee Millikin, spokeswoman for CH2M Hill Plateau Remediation Co.
"Ingestion is a very serious event," said Mike Korenko, a Hanford Advisory Board member, as the incident was discussed at the board's meeting Thursday. It is a matter of good conduct of operations and work discipline, he said.
"Obviously, we don't want any contamination to occur," Millikin said.
Several workers were removing portions of a highly contaminated HEPA filter attached to a glovebox in the Plutonium Finishing Plant, when the continuous air monitoring alarm sounded. They had been cutting the connection between a bag inside the glovebox and a bag outside the glovebox when one end slipped out from under a wet towel placed over the connection, and the alarm sounded.
They left the room and no contamination was found on their skin or personal clothing. They were wearing respirators and protective clothing over their personal clothing.
However, another alarm sounded in a room that was not planned to have airborne radioactive material where workers without respirators were helping remove the protective clothing of the glovebox workers. Nasal smears indicated radioactive material might have been inhaled by some of the workers.
Ten workers were further tested for plutonium ingestion, with two of them showing evidence of breathing in radioactive material.
CH2M Hill is focusing on the response to the alarm, Millikin said. Workers have had many briefings and every supervisor in the plant has been required to meet with the plant's deputy vice president, conduct of operations mentor and radiological control director to discuss expectations for the response to an alarm.
CH2M Hill also is looking at its rules for leaving contaminated areas when an alarm sounds and how to minimize contact with workers wearing less-protective gear.