The monitoring last year was conducted in the federal nuclear site by the state Department of Health, which notified the federal Energy Department of the findings in December.

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Monitors at the federal Hanford Nuclear site found plutonium and americium contamination up to 10 miles from a troubled demolition project that was suspended in December due to concerns about the spread of radioactive particles.

The monitoring last year was conducted in the federal nuclear site by the state Department of Health, which notified the federal Energy Department of the findings in December.

The state monitoring picked up signs of radioactive americium and plutonium particles from the demolition of the Plutonium Finishing Plant that appear to have spread over a far larger zone of the federal site than initially thought.

“We don’t want to see contamination outside the work-control zone, and this was in areas that you didn’t expect to see it. It was surprising,” said John Martell, manager of the radioactive air emissions section of the state health department.

Martell said the analysis was done on a composite of air filters that were changed every two weeks during the first six months of 2017. He said the federal Energy Department, in a statement released this week, incorrectly said the results reflected monitoring conducted since last June. He said that data is not yet available.

Martell plans to meet with federal officials to discuss the results on Friday. The test results do not identify the source of the contamination, but it is assumed to be from the Finishing Plant.

“It is not acceptable for contamination to be discovered outside of controlled cleanup areas,” says the statement released by the Energy Department.

Martell said the findings raise concerns that contamination could spread off site.

Meanwhile, the Energy Department this week started to release the results of bioassays of workers concerned the contamination made its way into their bodies.

Two of the first 91 workers who had bioassays tested positive for inhaling or ingesting contaminated particles, according to the Energy Department. The other 89 did not show signs of contamination.

Another 180 worker test results are expected to be received by early March.

This is the second round of worker testing to result from the demolition work at Hanford’s long-shuttered Finishing Plant. After a June contamination incident, bioassay tests indicated that 31 workers inhaled or ingested small amounts of radioactive substances.

The work at the finishing plant is a key part of the broader, decades-long effort to clean up the Hanford reservation, which produced plutonium for the atomic bomb dropped on Nagasaki, Japan, at the end of World War II, and then for the Cold War nuclear-weapons stockpile.

The finishing plant first went into operation in 1949 and shut down in 1989. Through the years, it expanded to include more than 60 buildings involved in producing plutonium buttons, roughly the size of a hockey pucks, that were shipped to weapons-production complexes.

The contamination problem appears to have resulted from the final demolition work on a structure where plutonium was reclaimed from scrap materials. That work has been put on hold with the sole focus now on workers’ safety and controlling the spread of contamination, according to the Energy Department statement.

According to the Nuclear Regulatory Commission, plutonium primarily emits alpha particles, which have a very short range. But it is toxic, “in part, because if it were to be inhaled it could deposit in the lungs and eventually cause damage,” according to a commission document on plutonium.