Hanford Site officials are investigating the possibility that a second double-shell tank at the Department of Energy facility may have a leak between its shells after unexpected radiation readings from the ventilation system of Tank AY-101’s annulus. However, results of a video inspection conducted in response to the readings showed no difference in the appearance of the annulus this month compared to other inspections using video cameras inserted into the annulus, or space between the shells, in recent years. Leak detection instruments located throughout the annulus also have not detected any liquid, according to the Department of Energy. The unusual readings showed radiation that was above the normal background level on filter papers installed on a continuous air monitor for the tank’s annulus. The levels were not high enough to trigger an alarm.
The Department of Energy has not ruled out any cause, said Tom Fletcher, DOE assistant manager for Hanford waste storage tank farms. Possibilities other than a leak include cross contamination between the annulus ventilation system and the ventilation system for the waste storage shell. It also could be historical contamination that had been in the annulus for some time, he said. A lab analysis found the contamination included cesium, americium, and plutonium.
The Washington state Department of Ecology had been notified and said information it had received so far did not indicate an interior leak in the tank. Tank AY-101 was the second of 28 double-shell tanks built at Hanford. Tank AY-102, the oldest double-shell tank, has been leaking waste from its primary shell over several years and is now being emptied. The waste dried in patches in the annulus that could be seen in inspections with video cameras. After work to retrieve sludge from the tank started this spring, the rate of leakage increased substantially.
Sen. Ron Wyden (D-Ore.) said in a statement Tuesday that he would ask the Government Accountability Office “to examine what and when DOE knew about the leaks in these tanks, the adequacy of the department’s tank safety efforts and responses to the deteriorating condition of all of the high-level waste tanks.” Wyden repeated the request he made last week for Energy Secretary Ernest Moniz to appoint an independent panel to analyze the safety of all of Hanford’s double-shell tanks. Watchdog group Hanford Challenge on Tuesday called for DOE to begin building new double-shell tanks immediately. “Simply put, Hanford is nearly out of double shell tank space, especially after pumping out AY-102,” said Tom Carpenter, Hanford Challenge executive director, in a statement.