Hanford tank farm workers performing routine tasks at the vast nuclear waste site reported getting sick after breathing chemical vapors on Thursday.

The toxic gases most likely escaped from pipes used to move nuclear waste from one area of Hanford to another. Transferring waste always increases the chance of employee exposure to vapors because of the complexity of moving highly radioactive, chemically contaminated nuclear byproducts from aging storage tanks.

Starting around noon, two employees reported a metallic taste in their mouths after removing their personal safety gear. They sought medical attention and the area they were working in, the AP tank farm, was evacuated.

Two hours later two more workers experienced nausea and a dry throat after being exposed to vapors above a line used to transfer waste between the AX and AP tank farms. The area they were working in was evacuated and road blocks were set up as extra precautions. These workers were sent to the onsite medical clinic as well.

Then between 3 pm and 4 pm seven additional workers near a changing trailer outside the AX farm requested medical attention after smelling the strong odor of ammonia.

After the exposures, some employees complained that full respiratory protection wasn’t mandated after the first two workers reported problems mid-day. They also objected to a decision to continue pumping and transferring waste.

“I think it’s stupid,” said one worker on the condition of anonymity. “If you know there are odors, and you’re expecting odors, wouldn’t you want to protect the workers?”

“It’s so irresponsible that WRPS (the government contractor) failed to take appropriate steps to protect workers even after more and more people got sick. What’s going on out there?” said Tom Carpenter, executive director of the Seattle-based citizen watchdog group Hanford Challenge.

The pumping and transferring activities were eventually halted.

“Waste transfer operations from double-shell tank AY-102 to double-shell tank AP-102 have been halted,” said WRPS executive Jerry Holloway in a statement to KING.

The vapor events are thought to be caused by the pumping of nuclear waste out of double shell tank AY-102. The KING 5 Investigators series “Hanford’s Dirty Secrets” exposed that WRPS knew or should have known that this double shell tank was leaking in 2011. The company and the U.S. Department of Energy waited a year before announcing the leak.

AY-102 is one of 28 underground double shell tanks holding the most radioactive and chemically contaminated waste at Hanford. The double shells were thought to be far more robust than the single shell tanks, which outlived their life span and have leaked into the ground. There are 177 underground tanks total.

After the admission that AY-102 had failed and waste from the primary tank was escaping into the tank’s safety space, the contractor and the Department of Energy were legally required to pump out the contents of the primary tank right away. That didn’t happen. The state of Washington sued the federal government to force the pumping, which finally began in March.

As AY-102 is pumped, the waste goes through transfer lines to a tank with extra space, AP-102. Since March, this operation has typically taken place on nights and weekends to limit the possibility of people getting exposed to escaping vapors as the waste is moved.

On Tuesday night, WRPS began pumping and transferring from AY-102. That continued until the exposure episodes on Thursday.

Thursday’s vapor exposures are the latest in a series of problematic events at the nuclear site in the last two weeks. On Tuesday, KING 5 broke the story that signs have emerged that a second double-shell tank, AY-101, is beginning to leak.

And last week the KING 5 Investigators found that the leak in AY-102 has greatly expanded since the pumping operation began.

The liquid nuclear waste held in underground tanks is the result of four decades of plutonium production at Hanford for the country’s weapons defense program. Plutonium produced at the site fueled the bomb dropped on Nagasaki in World War II. Production continued through the Cold War to build up the U.S. nuclear arsenal. Since 1989, the only work at Hanford has been related to cleaning up the waste left behind. The most dangerous byproducts are contained in the 56 million gallons of liquid waste housed in the aging underground tanks.