A dozen workers were evaluated Thursday for possible exposure to chemical vapors during work to empty the Hanford Site double-shell tank with an interior leak and transfer the waste to a sturdier double-shell tank. Pumping to remove waste from Tank AY-102 has been stopped due to the possible vapor issues, according to the Department of Energy. However, Hanford officials still planned to pump waste leaking into the area between the tank’s shells, called the annulus, back into the primary shell, if needed.
On Thursday afternoon, two workers in the AP Tank Farm reported smelling suspicious odors after they removed their self-contained breathing apparatus. They also reported headaches. Waste from Tank AY-102 was being transferred to an AP Farm tank and they had been wearing supplied-air respirators until they left a vapor control zone, an area where there was concern that chemical vapors could be detected because of work with the tank waste. Both workers were sent to the Hanford on-site medical center, where they were evaluated and then released. Six other workers left the AP Tank Farm, as is standard procedure when chemical vapors are suspected.
Shortly after that two more workers, both outside the AP Tank Farm, reported smelling an odor as they walked the transfer line between the AY and AP Tank Farms to conduct industrial hygiene monitoring. That was followed by at least one report of a suspicious odor outside a nearby tank farm, the AX Farm. All the workers who reported smelling vapors, along with several others who were working outside the AX Farm and one worker who had been driving on a road in the area, were sent for medical evaluations at the on-site medical provider. The outcome of their evaluations was not available Thursday night. Workers who smell vapors may report symptoms such as headaches, coughing, and nose bleeds, but there is concern that more serious health conditions could result in the long term from chemical exposure.
Tank farm contractor Washington River Protection Solutions (WRPS) and the Department of Energy have been sued in U.S. District Court for Eastern Washington by the state of Washington, watchdog group Hanford Challenge, and union Local 598, which seek increased worker protection from tank waste chemical vapors. WRPS commissioned an independent study led by the Savannah River National Laboratory in 2014 to better understand chemical vapor exposure. It has been implementing 47 recommendations in two phases. The proposed strategy has been to reduce the high reliance on personal protective equipment and administrative controls, such as ropes strung to keep workers from particular areas, in favor of engineered controls and technologies.
About 95 percent of the waste has been pumped from Tank AY-102 since early March. Updated estimates put the amount of waste before pumping started at 744,000 gallons, the majority of it liquid. Work had been advancing quickly until early last week to remove enough waste to determine the cause of the leak, as required under a settlement agreement with the state of Washington. The deadline to empty the waste is March 4, 2017.
But waste that had slowly leaked from the inner tank to dry in three places in the tank’s annulus over several years started leaking much faster the morning of April 17. It filled the annulus to a little more than 8 inches deep. Since then waste in the annulus has had to be pumped back into the primary shell of the tank multiple times as it reaches a little over 5 inches deep. The rate of leakage appears to increase as WRPS workers retrieve waste in the northeast portion of the tank, said Chris Kemp, deputy federal project director for tank retrieval and closure, at a Hanford Advisory Board committee meeting Wednesday. Sluicing systems at the top of the underground tank are used to spray liquid waste on the sludge remaining at the bottom of the tank to break it up and move it toward a pump.
The sludge that remains in the primary shell of the tank is no longer in an even layer. It is as deep as 20 to 30 inches near the sides of the tank and about 4 inches deep in the center of the tank, Kemp said. The rate of retrieval had slowed significantly as the volume of waste in the tank dropped, he said Wednesday. WRPS will consider carrying out an earlier plan that called for switching out retrieval equipment for an enhanced reach sluicing system that can extend to reach more areas of the tank, despite the quick start to sludge retrieval. Tests continue to show no sign that any waste has breached the outer tank to reach the environment.
Washington River Protection Solutions is charged with management of tank farms holding 56 million gallons of radioactive and chemical waste from Hanford’s former plutonium production operations. The material will ultimately be processed at the site’s Waste Treatment Plant.
