A check of monitors worn by Hanford tank farm workers has found no samples with chemicals close to the federal limit for occupational exposure, according to the Department of Energy.
However, there is the potential for reports of chemical vapors to increase with the planned startup Friday of the Hanford tank waste evaporator.
Since spring, 44 workers have received medical evaluations for possible exposure to chemical vapors from the waste held in Hanford's underground tanks. All have been cleared to return to work and a few of the potential exposures may have been linked to pesticide spraying rather than waste.
"As far as we can tell there have not been any long-lasting health effects," said JD Dowell, deputy manager of the DOE Office of River Protection, at a Hanford Advisory Board meeting Thursday in Pasco. Some previous workers have reported serious long-term health effects from chemical vapor exposure and precautions have been taken since then, such as evacuating tank farms when vapors are suspected.
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An analysis of 3,200 samples collected by monitors worn by workers found 19 that showed chemicals present at more than 1 percent of the occupational exposure limit, Dowell said. The samples were collected from April 1 to July 7.
Washington River Protection Solutions uses an administrative limit for occupational exposure to chemicals that is 10 percent of the federal standard set by agencies such as the Occupational Safety and Health Administration, Dowell said. Four of the samples were above 10 percent of the federal limit, Dowell said. Those included samples with asbestos, mercury and nitrous oxide.
There were no samples collected with chemicals at more than 50 percent of the federal occupational exposure limit, he said.
However, DOE remains committed to a conservative response to chemical vapors and to protecting workers, he said.
A draft report from an independent review to find solutions to chemical vapor issues is expected this month.
The exposures to vapors, as reported by workers who smell the vapors or become ill with symptoms such as dizziness and shortness of breath, are difficult to predict, Dowell said.
They have been reported all over the area of Hanford where 56 million gallons of waste has been stored in 177 underground tanks. And they do not necessarily correlate with conditions known to increase vapor releases from underground tanks, such as certain weather conditions and activities that disturb waste.
However, Hanford officials do know that there is an increased propensity for vapors when the 242-A Evaporator is operating, Dowell said. It was last operated in fall 2010 and in the years since has been given an extensive overhaul.
"We are taking special precautions to make sure workers are not exposed to vapors," he said.
Employee parking is being restricted near the evaporator and monitors have been set up there to detect chemicals. Hand-held monitoring also is planned, and results will be posted daily. Masks will be available for workers who wish to wear them.
Because waste will be transferred from nearby tanks to the evaporator and back again, there is potential for workers in nearby tank farms and near the evaporator, to smell vapors. The most common chemical reported in tank vapors is ammonia, which can be smelled at low concentrations, workers have been told.
The evaporator reduces the amount of liquid waste held in double-shell tanks, creating more storage space for waste retrieved from leak-prone single-shell tanks until the waste can be treated for disposal.
Hanford's 28 double-shell tanks are nearing capacity and the planned evaporator campaign should reduce the waste volume by more than 1 million gallons, the equivalent of a full double-shell tank.
A back-to-back evaporator campaign is planned with a first run removing about 800,000 gallons of liquid. The waste will be sent through the evaporator a second time to remove another 350,000 gallons of liquid. Work should be completed in mid-October.
-- Annette Cary: 509-582-1533; firstname.lastname@example.org; Twitter: @HanfordNews