Several Hanford workers breathed in radioactive contamination at the Hanford nuclear reservation's Plutonium Finishing Plant, according to newly completed laboratory tests.
The Defense Nuclear Facilities Safety Board reported the February event in the latest weekly staff report it has released, calling it a "significant contamination event."
The reports also stated that workers responded appropriately when the potential danger was discovered. The Department of Energy has called the Plutonium Finishing Plant Hanford's highest hazard facility.
Newly completed analyses of bioassays for 17 employees show that one worker had internal contamination with radiation roughly comparable to the radiation from one chest X-ray, said Terry Vaughn, vice president of safety, health, security and quality for CH2M Hill Plateau Remediation Co.
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That worker had a radiation dose of 15 millirem.
The Department of Energy limit for radiation exposure is 5,000 millirem per year, and CH2M Hill sets its administrative level at 500 millirem per year.
Another worker had a dose of 6 millirem, and two others had 2 millirem. In addition, five workers had doses of less than 0.5 millirem, and all others were negative.
"We're not happy about this," Vaughn said. "However, these doses are very low, well below regulatory limits or in-house administrative limits."
Work is planned and executed to try to control radiological work to prevent internal or skin contamination, he said.
Last month's incident happened in a room that was checked and found free of any loose contamination, Vaughn said.
Workers entered wearing two sets of protective clothing but no respirators to prepare for the removal of contaminated piping, according to the defense board staff report. However, a radiological controls technician discovered contamination and directed the work team to evacuate.
During the evacuation, significant contamination was found on the protective clothing of one worker, the report stated. Nasal smears were taken, and one smear tested positive.
It was a textbook response by the radiological controls technician, Vaughn said.
"DOE agrees with the DNFSB that the contractor and its employees responded appropriately to the event," said DOE spokesman Geoff Tyree.
Bioassays were done for all 15 workers who were in the room, plus two others who requested the checks as a precaution.
"The contamination spread appears to be related to disturbing fixed contamination in the work area, and this hazard may not have been adequately evaluated during the work planning process," the defense board staff report stated.
CH2M Hill believes that as scaffolding was put up in the room, a flange that couples the air handling system together was bumped, which may have released some contamination. At least one loose bolt was discovered, Vaughn said.
The area has been decontaminated and all bolts on the flange are being checked, Vaughn said. Work has not been restarted.
-- Annette Cary: 582-1533; firstname.lastname@example.org