Hanford radiological control technicians who questioned some unusual radiation readings are being credited with discovering the breach in a waste storage tunnel at Hanford this week .
“Congratulations to employees who were very astute,” said Doug Shoop, manager of the Department of Energy Richland Operations Office.
He spoke publicly for the first time since the partially collapsed tunnel was discovered on Tuesday, as he and other officials returned to Richland after taking Sen. Maria Cantwell, D-Wash., onto the nearby Hanford nuclear reservation for a briefing and look at the tunnel Saturday morning.
“I’m thankful that no one has been hurt and (there was) no immediate harm to the environment,” Cantwell said. “But the incident is a harsh reminder that we need to stay on top of all our efforts at Hanford.”
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Temporary stabilization of the tunnel that partially collapsed could be completed in the coming week, Shoop said.
Technicians were doing radiation monitoring Tuesday morning to make sure the area was safe before planned maintenance work around the PUREX plant complex in central Hanford, he said.
When some readings were much higher than expected, they began checking for the cause and found one anomaly.
At a distance, there appeared to be a depression in the berm atop the oldest of two PUREX processing plant tunnels, used for long-term storage of equipment with high levels of radioactive contamination.
There is potential for more collapse.
Doug Shoop, manager of the DOE Richland Operations Office
Initial DOE statements during the chaotic hours of the emergency declaration indicated there were no radiation readings above normal background levels.
The radiation “shine” noticed by the technicians, similar to radiation from X-rays, was not at levels that would have harmed them, Shoop said.
Further evaluation showed that an area of the roof about 20-feet-by-20-feet had collapsed, and about eight feet of dirt that formed the berm over the top of the tunnel had fallen into the cavity.
More worrisome than radiation shine was the possibility of airborne releases of loose contamination, such as dust contaminated with radiological material that could be inhaled.
Both DOE and state officials continue to say that no airborne contamination was detected.
Federal and state monitoring data from the incident should be publicly available within a few days, Shoop said.
Exactly when the breach occurred is not yet known.
DOE performed a formal surveillance of the waste tunnel, as required annually by its federal Resource Conservation and Recovery Act permit, in December.
In March, aerial photographs were taken of the tunnel and showed no evidence of a break, Shoop said.
Although there have been media reports that the tunnel was last checked four days before the breach was discovered, Shoop said putting a firm date on the last time the tunnel was confirmed to be intact continues to be investigated.
He is confident that there was no airborne release of contaminated material before the breach was discovered, however.
We had some very, very high winds after the hole was filled. It could be a very different situation if … that hole was still open.
Doug Shoop, manager of the DOE Richland Operations Office
Many samples of material, such as dust, have been collected near the breach and from surrounding areas with no indication of a spread of contamination, he said.
In addition, routine daily and weekly monitoring is done across the nuclear reservation, he said.
Shoop praised the quick work to fill the breach.
Crews worked through the night Tuesday to build a gravel road to get heavy equipment to the area of the breach. Before midnight Wednesday, 53 truckloads of sand mixed with a little soil had been shoveled into the hole using an excavator and scoop.
“We had some very, very high winds after the hole was filled,” Shoop said. “It could be a very different situation if … that hole was still open.”
Crews were working over the weekend to haul in large concrete “ecology blocks” for the next step to stabilize the breached tunnel.
“There is potential for more collapse,” Shoop said.
DOE plans to place a plastic cover over the nearly 360-foot tunnel next week, if the weather clears. Possibly rainy and windy weather is forecast for at least part of the week.
Only a day or two may be needed to cover the tunnel once work starts.
The plastic will be laid over the tunnel like a tarp, but will be more robust than a conventional tarp, Shoop said. The concrete blocks will hold it in place.
As recently as February, an emergency exercise in central Hanford used the scenario of a single-engine aircraft crash into one of the PUREX waste tunnels, causing a breach and radioactive release.
The covering will keep any precipitation from the soil over the roof of the tunnel, which would add to the soil’s weight.
Although no cause for the collapse has been determined, winter weather was unusually wet and snowy across Washington state.
No decision has been made on whether to cover a second waste storage tunnel at PUREX, which is about five times as long.
The first tunnel was built of timbers, but the second tunnel built in 1964 was built of steel and concrete and possibly used as recently as the 1990s.
The oldest tunnel was filled from June 1960 to January 1965, with eight flatbed rail cars loaded with large pieces of equipment and tanks.
Good records were kept, indicating the material on the rail cars was “very radioactive,” Shoop said. The waste apparently was not placed in containers that could have provided shielding from radiation before being placed on the rail cars.
Covering the oldest tunnel is only an interim step to stabilize it.
DOE is discussing longer-term plans with the state Department of Ecology, Shoop said.
DOE may propose filling the tunnel with grout as a next step.
The state agency, a Hanford regulator, issued a legal order Wednesday setting deadlines for DOE to determine the cause of the collapse, ensure the contents of the tunnel are stored safely and to submit a plan for permanent cleanup of the radioactive material in the tunnel.
The Central Washington Building and Construction Trades Council is satisfied with the stabilization steps that have been put in place.
Michael Bossé, council president
When an emergency was declared Tuesday morning at Hanford, a siren sounded and a loud speaker blared “take cover.”
More than 3,000 workers spent as long as several hours in buildings with ventilation systems shut off as protection from possible airborne contamination.
As recently as February, an emergency exercise in central Hanford used the scenario of a single-engine aircraft crash into one of the PUREX waste tunnels, causing a breach and radioactive release. In 2013, an emergency drill used the scenario of an earthquake that caused a tunnel to collapse.
Top Hanford union officials who met with Cantwell on Saturday said they approved of DOE’s response to the emergency.
“The Central Washington Building and Construction Trades Council is satisfied with the stabilization steps that have been put in place,” said Michael Bossé, council president.
Jeff McDaniel, the new president of the Hanford Atomic Metal Trades Council, said he had not heard complaints from HAMTC workers.
Sampling and surveying work has gone smoothly, and DOE has put a lot of energy into its response to the tunnel breach, he said.
A couple of hundred workers at the Hanford tank farms near the tunnel collapse had not been instructed to return to work at the end of last week, as efforts to stabilize the breach continued.
Cantwell said she will continue to make the case to the administration of President Donald Trump that adequate funding is needed to meet the nation’s obligation for Hanford environmental cleanup.
Hanford produced plutonium for the nation’s nuclear weapons program from World War II through the Cold War.