Significantly more waste has leaked from the inner tank of double-shell waste storage Tank AY-102 as Hanford workers pumped radioactive sludge from the tank this weekend.
None has been found to have leaked from the tank into the soil beneath it as of early Monday morning, but checks are ongoing, according to Department of Energy contractor Washington River Protection Solutions.
The tank, Hanford’s oldest double shell tank, was being emptied because it had waste leaking into the space between its shells in three places. About 70 gallons of waste had been estimated to have leaked, drying in three separate patches.
However, this weekend as sludge was being pumped from the tank, an alarm for a level detector in the space between the shells sounded.
The waste appeared to have filled the space between the shells of the 1-million-gallon capacity tank to about eight inches deep.
Several hours later the waste level then dropped slightly more than half an inch.
Hanford workers found no waste outside the tank in the leak detection pit in an initial check Sunday. That does not rule out that waste may have leaked somewhere else from the tank.
Another possibility is that some waste has flowed into the ventilation channels in the platform the inner shell sits on above the outer shell, reducing the level of waste being measured in the space between the tanks.
Pumping to empty the tank stopped when the increased leakage was detected.
Before waste retrieval started, pumping equipment was installed into the space between the shells as a precaution in case waste retrieval pumping increased the rate of leakage. That equipment is being prepared for use.
The Washington State Department of Ecology, the regulator on the project, has been working with Hanford officials since Sunday. The state says there is no danger to workers or the public.
The increased rate of leakage likely occurred because waste retrieval work inside the tank dislodged material that was partially blocking leak sites, according to the Department of Ecology.
That was known to be a possibility before sludge removal started and a contingency plan was developed to address it, the state said.
This story will be updated.