Work to empty a Hanford tank with an interior leak has been stopped after several workers reported suspicious odors that may have been from chemical vapors on Thursday.
A total of 12 workers were taken for on-site medical evaluations, according to information available Thursday evening.
The first two workers had been wearing respirators with supplied oxygen because they were in an area designated as a vapor control zone. Work was being done that could increase the risk of chemical vapors in the air.
After leaving the vapor control zone early Thursday afternoon, they took off their respirators and smelled odors. They also reported having headaches.
Work was underway Thursday to remove waste from double-shell tank AY-102, which is leaking waste from its interior shell into the space between its shells. The waste was being transferred to a nearby group of tanks, the AP Tank Farm, to be stored in a sturdier double-shell tank.
The workers who smelled the odors were in the AP Tank Farm. They were sent to the Hanford on-site medical provider for evaluations and had been released by the end of the day.
Six other workers who were in the AP Tank Farm when the odors were detected also left the farm, as is Hanford policy, according to a statement from the Department of Energy.
Most of the workers checked for possible chemical vapor exposure were outside tank farm boundaries.
Shortly after that, two additional workers who were walking the line that transfers the waste to the AP Tank Farm to monitor it smelled an odor, according to a memo sent to Washington River Protection Solutions workers. The workers, both industrial hygienists, were outside the AP Tank Farm.
By mid-afternoon at least one other worker outside a nearby tank farm smelled an odor.
Those additional workers, plus several others in the area, went to the on-site medical provider for evaluations. One had been in a vehicle driving through the area.
The results of 10 of the evaluations were not available yet Thursday evening.
Concerns have been raised that workers exposed to chemical vapors could develop serious, long-term medical issues.
Washington River Protection Solutions has required supplied-air respirators for much of the work in the tank farms while it implements recommendations from an independent report to better protect workers.
A multi-year plan was announced in February 2015 to address the 47 recommendations in the report. The plan calls for expanded data collection, new research studies and new technologies.
95 percent of 744,000 gallons of waste removed from Tank AY-102
The state of Washington, Hanford Challenge and Local Union 598 have filed lawsuits to better protect workers from chemical vapors.
Pumping to remove waste from tank AY-102 was stopped Thursday afternoon. However, pumping will be done as needed to remove leaking waste as it accumulates in the space between the tank’s shells.
Tank AY-102 has had a slow leak for several years and DOE is required by a settlement agreement with the state to have it emptied enough to determine the source of the leak by March 4, 2017.
Since early last month, Hanford workers have removed about 95 percent of the waste in the tank. Updated estimates put the amount of waste in the tank before retrieval started at 744,000 gallons.
Work initially had been done mostly on weekends when few workers were on site, with checks after the weekends of monitoring data collected for chemical vapors.
Waste retrieval was advancing quickly until April 17, when an alarm sounded, indicating that the rate of leakage into the space between the shells, called the annulus, had significantly increased.
Until then, waste had leaked and dried in three patches in the annulus. But waste retrieval work apparently caused more waste to leak, filling the annulus to about 8.3 inches deep.
As a precaution, a pump had been placed in the annulus before waste retrieval from the main shell began. It continues to fill, with waste pumped out each time it reaches a little more than 5 inches deep.
That last little bit is going to take some time.
Chris Kemp, DOE
The rate of leaking seems to increase as operators work to remove the waste in the northeast section of the tank, said Chris Kemp, the DOE deputy federal project director for tank waste retrieval at Hanford.
Workers have reduced the waste to about four inches in the center of the tank, but it remains 20 to 30 inches deep at the edges of the tank. Sluicing systems at the top of the tank are used to spray liquid waste on the sludge remaining in the tank to break it up and move it toward a pump for removal.
“That last little bit is going to take some time,” Kemp told a Hanford Advisory Board Committee on Wednesday.
Washington River Protection Solutions, the DOE contractor on the project, had initially planned to switch to an enhanced reach sluicing system that can reach to more parts of the tank by late spring or early summer.
Hanford officials are again considering switching to the enhanced reach technology as the rate of retrieval has slowed.
There is no evidence that any waste has breached tank AY-102’s outer shell to reach the environment.