The Department of Energy hopes to be able to determine in the next several weeks if radioactive material detected in the space between the inner and outer layers of one of Hanford’s double-shell tanks is from an actual tank leak. Earlier this month, a video inspection conducted at Tank AY-102 found material in two locations of the tank’s annulus, according to a DOE document made public late last week by the watchdog group Hanford Challenge. The discovery is the first time material has been discovered outside the primary wall of one of the double-shell tanks DOE is using to store radioactive waste taken from Hanford’s single-shell tanks, raising questions over the integrity of the aging double-shell tanks. DOE has stressed, though, that the material is dry and did not breach the outer shell of the tank, and does not pose a threat to Hanford workers, the public or the environment.
Tank AY-102, which was put into service in 1971, has a capacity of 1 million gallons, and currently holds approximately 857,000 gallons of waste. According to the DOE document, the material discovered in the tank annulus consists of a “mound” measuring 2 feet by 3 feet by 8 inches and “white material” found on the tank refractory and the annulus floor. In a message to employees late last week, DOE Assistant Manager for Tank Farms Tom Fletcher said, “Analysis of samples taken near the material show higher-than-expected contamination levels. Until we learn more about this material and begin to understand the source, we are increasing the monitoring frequency of AY-102. In addition, we are actively working to characterize the material to determine the appropriate next steps, and visually inspecting all accessible areas within the tank to ensure no other material is present.” Fletcher also said. “This is the first tank to show signs of aging. Events such as this reinforce the importance of safely emptying all the Hanford waste storage tanks as quickly as possible and convert the waste into a stable form for safe, long-term storage.”
DOE is now working to determine if the detected material came from a leak in the inner layer of the tank, or from another source, such as cross contamination from a pit with pumps or piping where there could have been a spill. DOE hopes to be able to determine the source of the material by the end of September, Fletcher told WC Monitor yesterday. “If this is a leak, it’s from the bottom and that’s a bad situation.” he said. Fletcher also noted, “If it’s a leak, it’s very, very slow.” The Washington State Department of Ecology “views this issue very seriously and will be urging DOE to move rapidly on doing detailed characterization of the material and detailed evaluation of the tank,” Cleanup Section Manager Cheryl Whalen said in a written response to WC Monitor. She added, “Ecology will also be looking into the leak detection systems and maintenance records to make sure this type of incident is detected and addressed at any other tanks. The loss of use of any DST will be a serious blow to SST retrievals.”
Hanford Challenge Executive Director said the discovery increases the need for new double-shell tanks to be built at Hanford. “These tanks were supposed to last another 40 years, but that thinking has been superseded by this new reality,” Carpenter said in a press release late last week. “This new evidence gives urgency to the suggestion that the DOE build more tanks. We always knew the Double Shell Tanks would leak, we just did not know when. We have the first, how many will be leakers in another 40 years? The only good news here is that the waste from this tank leak was not in liquid form, and is apparently not yet affecting the environment.”