The secondary bottom of a double-shell tank at the Hanford Site “has likely failed,” the Washington state Department of Ecology said last week in a letter to the Department of Energy. There is no sign, though, that any radioactive waste is leaking out of the tank into the environment, officials said Friday.
The specific concern is that a small portion of the secondary tank bottom appears to have thinned by more than 70 percent, based on results from ultrasonic testing of the space between the two shells. Ecology believes this is due to groundwater infiltration under the tank and the amount of liquid in the tank’s leak detection pit.
Tank AP-102 holds sludge removed from another double-shell tank, AY-102, which was emptied after waste was found to be leaking between the tanks. The sludge had initially been held in a separate single-shell tank and produces a significant amount of heat. “As a result, the waste temperatures measured in AP-102 are now increasing, which will further accelerate the corrosion rate,” Jeffery Lyon, tank systems operation and closure project manager for Ecology’s Nuclear Waste Program, stated in an Aug. 14 letter the heads of DOE’s Office of River Protection and Hanford tank farm contractor Washington River Protection Solutions.
Hanford’s tank farms hold roughly 56 million gallons of radioactive and chemical waste produced by decades of plutonium production at the sprawling facility near the city of Richland. Taking Tank AP-102 out of service, Lyon wrote, would have a notable effect on Hanford’s Direct-Feed Low Activity Waste program — the program to begin processing such waste for permanent storage as early as 2022.
Ecology directed DOE to submit a plan for evaluating the integrity of Tank AP-102’s secondary containment by March 31 of next year. A final report on the tank’s secondary containment integrity from an independent qualified registered professional engineer is due by Sept. 30, 2018.
Both WRPS and DOE issued statements Friday emphasizing the absence of leaks in the tank. “The inner shell of the tank continues to safely hold the radioactive and chemical waste,” DOE said. “There have been no indications of any breach in the inner tank shell nor any indications of waste leaking into the tank annulus.”
