Hanford workers began pumping radioactive sludge Thursday evening from a double-shell waste storage tank at the nuclear reservation with an interior leak.
By 2 p.m. Friday, contractor Washington River Protection Solutions had retrieved about 14,500 gallons of sludge from the tank and work planned to continue through April 3.
“We’re pleased to have begun sludge retrieval and with the progress being made,” spokesman Jerry Holloway said.
The Department of Energy reached a settlement agreement with the state of Washington to start emptying waste from Tank AY-102 by March 4, 2016, and have the tank emptied by March 4, 2017. Waste is leaking from the tank’s inner shell but is still contained within the outer shell.
The tank farm contractor met the start deadline and removed about 550,000 gallons of liquid waste from the tank between March 3 and 9, transferring it to a sound double-shell tank near Hanford’s evaporation facility. The liquid waste volume will be reduced there.
But removing about 151,000 remaining gallons of sludge was expected to be tougher work.
Attempts were made on the next three weekends to start retrieving sludge.
Each time, there were equipment issues.
On the first weekend there was a problem with a meter needed to verify flow rates. The next weekend, the system had software issues. The third weekend, there was an issue with the slurry pump in the double-shell tank where the retrieved sludge was planned to be sent for storage.
“This is not uncommon when we start up retrieval with new equipment,” Holloway said. “A certain amount of troubleshooting is common.”
Washington River Protection Solutions planned to start sludge retrieval on a weekend when few workers were on site, then stop and evaluate data from monitoring and sampling for chemical vapors on the project to determine whether protective measures needed to be adjusted.
Among steps taken this weekend was requiring workers in the tank farms involved to wear supplied air respirators.
Zones were established where workers without appropriate respiratory equipment are not allowed. The zones are in places where exhausters are outside tank farm fences or so near tank farm boundaries that a zone was needed to cover nearby area outside a tank farm.
Traffic was restricted on some roads in central Hanford, including a road that a transfer line crosses beneath.
Although sludge was not retrieved during the past three weekends, some additional liquid waste was removed. Some waste volume also was lost to evaporation in the high heat tank.
The sludge is being transferred through above-ground transfer lines to a double-shell tank closer to the Hanford vitrification plant, which is planned to eventually glassify the waste for permanent disposal.
Tank AY-102 is Hanford’s oldest double-shell tank. Workers had numerous problems as they built it.
Emptying the tank, which has held waste since about 1970, will allow it to be inspected to learn what caused the leak. That could provide helpful information regarding Hanford’s other double-shell tanks, according to DOE.
It is estimated to have leaked about 60 gallons of waste that have been found in three places in the space between the tank’s shells as of the end of 2015.
Hanford has 27 double-shell tanks still being used to hold waste emptied from leak-prone single-shell tanks, some of which have held waste since World War II. The waste is left from the past production of plutonium for the nation’s nuclear weapons program.