More radioactive waste has been found leaking between the shells of Hanford's oldest double-shell tank.
The Department of Energy confirmed in October 2012 that Tank AY-102 had waste in two places between its shells.
Wednesday, DOE learned that waste had been discovered in a third place, said JD Dowell, deputy manager of the DOE Office of River Protection.
Dowell made the announcement at a Hanford Advisory Board meeting Thursday and said Energy Secretary Ernest Moniz was scheduled to be briefed later in the 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 scheduled to deliver today.
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 was lowered down the riser closest to that spot, the new dried waste was found. The area had appeared to be clear in September 2012 when video was shot using the same riser, according to DOE.
The newest pool of dried waste is estimated to 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 was last done in September 2012. The inspection is expected to take several months as video cameras are sent down multiple risers in a radioactive environment.
DOE can only say now that "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.
No waste is believed to have escaped into the soil beneath the tank.
DOE has 28 double-shell tanks built between 1969 and the mid-1980s that are used to hold waste emptied from Hanford's older leak-prone single-shell tanks. At least one of those tanks is believed to be leaking waste into the soil and 67 of 149 single shell tanks are suspected of leaking in the past before much of their liquid was removed.
Tank AY-102, built in 1969, already has held waste longer than its 40-year design life.
DOE has installed a pump that could be used to 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 be left 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 that it would need another 18 to 20 months to prepare to also remove sludge from Tank AY-102.
But state regulations require DOE to inspect a double-shell tank to determine the cause of the leak within 24 hours of discovering a leak or as early as possible. That includes removing as much of the waste as necessary to allow for the inspection, according to the state.
DOE does not know the location of the leak, the rate of leakage or conditions at the leak site within the tank, the state said in January in a letter to DOE. DOE also does not know when or how the leak might worsen, it said then.
There are risks to waiting to empty the tank, the state said.
The leak has the potential to clog ventilation channels, undermining the ability to moderate the heat in the tank and leading to greater corrosion of the tank bottom.
-- Annette Cary: 582-1533; email@example.com; Twitter: @HanfordNews