The Defense Nuclear Facilities Safety Board can’t determine the potential safety implications of removing a portion of the liquid radioactive waste stored in a damaged double-shell tank at Hanford, the DNFSB told the Department of Energy late last week. Tank AY-102 has been found to be leaking material into the space between the tank’s inner and outer layers, and in response DOE has been making plans to remove a portion of the liquid material on top of the sludge waste contained in the tank. A report prepared by Hanford tank farms contractor Washington River Protection Solutions recommended decanting the liquid layer from 270 inches to 96 inches, finding that such a move would have “little effect” on tank waste temperatures or the estimated leak rate, according to a Nov. 1 letter from DNFSB Chairman Peter Winokur. The Board, though, “determined that insufficient information exists to support this conclusion,” Winokur wrote.
The WRPS report “does not address key technical uncertainties” with the condition of Tank AY-102, such as the specific cause of the discovered leak, the leak rate, the chemical and physical conditions at the leak site and the potential impacts of changes in temperature, pressure or chemistry at the leak site, Winokur wrote. "If DOE proceeds with radioactive liquid decanting, the Board advises DOE to closely monitor for signs of increased leakage and blocakage of the insulating refractory slots that distribute cooling air to the tank bottom," he wrote. DOE’s Office of Environmental Management did not respond to requests for comment on the Board’s letter yesterday.
