Nitrous oxide test results encouraging

Initial results of expanded vapor monitoring near Hanford’s underground waste tanks show low levels of one gas that had been of potential concern, the Energy Department and the contractor handling tank cleanup said Monday.

Last month, contractor CH2M Hill required workers to wear respirators with supplied air tanks when working near some tanks due to concerns about nitrous oxide vapors from single-shell tanks and double-shell tanks that lack ventilation.

The supplied air was required because there is no commercially available respirator cartridge that filters nitrous oxide.

More recently, workers have been wearing individual monitors near their faces to sample for nitrous oxide, ammonia and organic chemical vapors. More than 150 samples have been taken, with 56 showing no detectable levels of nitrous oxide, CH2M Hill said Monday. Two showed slightly elevated concentrations. Other sample tests are pending.

Nitrous oxide, often referred to as “laughing gas,” sometimes is used by dentists. In proper concentration, it causes temporary general anesthesia. The Occupational Safety and Health Administration has no established limit for nitrous oxide concentrations.

The heightened monitoring comes amid allegations that workers at the Hanford Nuclear Reservation’s so-called tank farms are being endangered to speed up cleanup of the nation’s most contaminated nuclear site.

About 53 million gallons of radioactive liquid, sludge and salt cake are stored in 177 underground tanks less than 10 miles from the Columbia River. Plans call for turning much of that waste into glass logs and burying it in a nuclear waste repository.

CH2M Hill and the Energy Department, which manages the cleanup, say most of the chemicals are diluted and pose no danger to workers. But critics say too little is known about the waste to rule out any danger.

“The goal is to lower the level of concern and raise their confidence that the chance of them being exposed to something permanently harmful is essentially nonexistent,” said John Swailes, the Energy Department’s assistant manager for tank farms.

CH2M Hill also placed monitors in the workers’ breathing space within five feet of the tanks. They showed nitrous oxide concentrations far below levels that would cause long-term health effects, said Dale Allen, a senior vice president for CH2M Hill.

Monitoring will continue for weeks and perhaps months, Allen said.

“The issue is about allowing the workers to be fully engaged in reviewing all the data and gaining the confidence that the environment they work in is safe to work in,” he said.

More than 800 people work at the tank farms for CH2M Hill. The total work force at Hanford is about 11,000.

For 40 years, the Hanford reservation made plutonium for the nation’s nuclear weapons arsenal. Today, work there centers on a $50 billion to $60 billion cleanup, to be finished by 2035.