More radioactive waste is leaking between the shells of Hanford’s oldest double-shell tank.
The Department of Energy (DoE) confirmed in October 2012 that Tank AY-102 had waste in two places between its shells.
This past Wednesday, DoE found out waste was in a third place, said J.D. Dowell, deputy manager of the DoE Office of River Protection.
Dowell released the news at a Hanford Advisory Board meeting Thursday and said they would brief Energy Secretary Ernest Moniz later on that day.
“We just further believe this reinforces the need to pump this tank. We are really concerned,” said Jane Hedges, the director of the Washington State Department of Ecology’s Nuclear Waste Program.
The state had criticized DoE in January for its plan to monitor the waste but take no action unless conditions worsened. The state asked for a plan to pump waste from the tank, which DoE already was going to deliver.
Hanford workers spotted the new waste during a biweekly inspection of the largest pool of dried waste in the underground tank’s annulus, or the space between its shells. A video camera lowered down a riser that provides access to the annulus showed a shadow in a place previously thought to be bare.
When a video camera ended up lowered down the riser closest to that spot, they discovered the new dried waste. The area had appeared to be clear in September 2012 when they shot video using the same riser, according to DoE.
The newest pool of dried waste should cover an area about 7 feet by 21 inches and less than an inch deep. It’s about 31 feet from the largest pool of dried waste, which is 25 feet long and about the same width and depth. The other waste site is similar in size to the newest one.
DoE has directed its contractor, Washington River Protection Solutions, to do another complete inspection of the tank’s annulus, which last occurred in September 2012. The inspection should take several months as video cameras end up sent down multiple risers in a radioactive environment.
DoE can only say now “there is a change of conditions” in the tank annulus. It does not know if there are multiple leaks from the inner shell or — as some Hanford officials believe is more probable — one leak coming into the annulus in different places.
The inner shell sits on a ceramic refractory between the bottom of the inner and outer shells. It has ventilation slots for cooling air and pathways that allow waste to escape to the base of the circular annulus between the two shells. The tank has a 75-foot diameter.
They believe no waste escaped into the soil beneath the tank.
DoE has 28 double-shell tanks built between 1969 and the mid-1980s used to hold waste emptied from Hanford’s older leak-prone single-shell tanks. At least one of those tanks is leaking waste into the soil and 67 of 149 single shell tanks could have ended up leaking in the past before workers removed much of their liquid.
Tank AY-102, built in 1969, already has held waste longer than its 40-year design life.
DoE installed a pump that could remove liquid waste from the double-shell tank.
However, as long as 151,000 gallons of radioactive sludge remain in the tank, some of the 680,000 gallons of liquid it also holds must remain in the tank to help cool it. The sludge generates heat as it radioactively decays, and heat can increase corrosion rates in the tank and contribute to generating potentially flammable hydrogen gas.
DoE estimated at the start of the year it would need another 18 to 20 months to prepare to also remove sludge from Tank AY-102.