A vent-tube extension that raises the level of a tube that vents chemical vapors from an underground tank containing nuclear waste is shown at upper left, braced by a metal frame and cables at the "C"... more 
A vent-tube extension that raises the level of a tube that vents chemical vapors from an underground tank containing nuclear waste is shown at upper left, braced by a metal frame and cables at the "C" tank farm at the Hanford Nuclear Reservation, Wednesday, July 9, 2014 near Richland, Wash. The vent was raised several years ago in efforts to reduce worker exposure to harmful vapors. Officials said Wednesday that 12,000 air samples taken at Hanford this year after more than three dozen workers reported being sickened by chemical vapors have failed to find a cause for the problem. Journalists were only allowed to visit the normally bustling tank farm worksite during a lunch break when only two workers were present. (AP Photo/Ted S. Warren) less 
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Associated Press | Photo By Ted S. Warren
Wed, Jul 9, 2014 8:03 PM EDT