RICHLAND (AP) — Work on a major demolition project on the Hanford Nuclear Reservation was halted for two days this week after air monitors worn by several workers showed they might have inhaled radioactive particles.
Workers late Thursday were cleared to return to the demolition of the Plutonium Finishing Plant, which for decades was part of the nation’s nuclear weapons production complex.
The U.S. Department of Energy has called the work at the Plutonium Finishing Plant the most hazardous demolition project on the sprawling site.
The Tri-City Herald reports the plant is contaminated with plutonium, and the particles can easily become airborne.
“We take this very, very seriously,” said Ty Blackford, president of Energy contractor CH2M Hill Plateau Remediation Co. “We are dealing with a form of contamination that is very, very hard to manage.”
Lapel monitors worn by six workers at the Plutonium Finishing Plant complex have tested positive for radioactive particles at levels of concern, according to laboratory results. The highest potential exposure was 11 millirems for one of the workers.
For comparison, the average person in the United States is exposed to 300 millirems of radiation annually from natural sources, such as radon or radiation bombarding Earth from outer space.
Workers wear the monitors near their faces as a check for airborne radioactive particles that could be inhaled.
On Wednesday morning, lab results for four lapel monitors worn Tuesday came back positive.
The finding was unusual enough for CH2M officials to call a halt to the demolition project, Blackford said.
The Hanford Atomic Metal Trades Council also issued a stop work order for its employees about noon Wednesday. HAMTC is an umbrella group for about 15 Hanford unions.
Surveys found no contamination on workers’ skin or protective clothing, the newspaper reported.
Of the four positive tests on lapel monitors worn Tuesday, all but one was determined to have been triggered by naturally occurring radon, the newspaper reported.
The fourth test result was the one that measured 11 millirems of possible internal contamination. However, further testing showed that part, but not all, of the reading likely was because of radon.
That left four lapel monitors worn earlier with elevated readings that indicate workers were at risk of inhaling radioactive contamination.
The contractor recommended bioassays — checks of human waste for radiological contamination within the body — and the workers elected to have the checks. Results are expected in January, according to the Energy Department.
Demolition of the plant began in November 2016. About two-thirds of the nation’s plutonium for the nuclear arsenal came from Hanford.
