Mistakes and mismanagement are to blame for the exposure of Hanford workers to radioactive particles in December, according to a new report.
The primary radioactive air monitors used at a highly hazardous Hanford project were not up to the job, said the report.
Then when the spread of contamination was detected, the steps taken to contain it didn’t fully work. Mistakes on the project included diluting fixative, against the manufacturer’s recommendation.
Contractor CH2M Hill Plateau Remediation Co. on Thursday released its evaluation of what went wrong in December during demolition of the nuclear reservation’s highly contaminated Plutonium Finishing Plant.
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Radioactive particles were found well beyond the demolition zones where they were supposed to be contained. They spread across Hanford streets, were found at other Hanford projects, and — in air samples collected over months — were detected in very small amounts near areas where the public is allowed.
At least 11 Hanford workers checked since mid December inhaled or ingested small amounts of radioactive particles. Private and government vehicles were contaminated with radioactive particles, and some were driven into the Tri-Cities.
Before the December spread of contamination, Hanford officials were relying primarily on continuous air monitors that check for airborne radioactive contamination in near real-time and sound an alarm if workers may be in danger, the report said.
The monitors had worked in the past, including in June, when alarms sounded and workers were told to shelter in place.
The project was in the challenging position of achieving safe and controlled demolition while attempting to maintain schedule progress, which included completion of (legal) milestones and contractual commitment dates.
Root Cause Evaluation Report on Plutonium Finishing Plant contamination spread
But the monitors did not detect airborne contamination in December, possibly because some of the particles that spread were too heavy to stay aloft.
Officials had other signs that there might be a problem, including contamination found in monitors that workers wear on their lapels, yet continued to rely on the continuous air monitors.
“Some amount of contamination is anticipated during open-air demolition, and each event was treated as a discrete event, individually discussed, and actions taken with apparent success,” according to the report.
Responses to contamination events that did not include an alarm sounding became routine, and the events came to be seen as normal, the report said. The risk was not fully analyzed, documented or controlled, it said.
A month before the December spread of contamination, some Hanford radiological control workers identified an increase in contamination issues. But management at the plant thought that contamination could be contained by applying more fixative, the report said.
“The project was in the challenging position of achieving safe and controlled demolition while attempting to maintain schedule progress, which included completion of (legal) milestones and contractual commitment dates,” the report said.
A decision was made to speed up demolition, based in part on the lack of alarms from the continuous air monitoring system.
Exhausters had been placed inside the most contaminated part of the plant, the Plutonium Reclamation Facility, to create negative air pressure and help prevent the spread of contamination.
But as more of the facility was torn down, the less effective the exhausters were in creating negative air pressure.
A decision was made to rapidly demolish the rest of the facility, on the assumption that contamination was more likely to become airborne from a partially demolished structure than from a pile of rubble on the ground.
Earlier in the demolition process, rubble was quickly packaged rather than piling up on the ground.
With faster demolition, the rubble would accumulate but could be covered with paint-like fixative and eventually with a temporary layer of soil, Hanford officials decided.
They incorrectly thought that fixative would contain any contamination, the report said. But the review found that while the front of a piece of debris might be covered, the spray of fixative might miss the back side.
The risk of contamination becoming airborne from rubble piles had been calculated, but it did not take into account the large amount of rubble that would be on the ground at one time after demolition sped up, the report said.
Fixative also had been sprayed on the higher portion of the Plutonium Reclamation Facility to contain radioactive contamination as it was demolished.
Because the fixative was too thick to be pumped, it initially was diluted to a mix of 25 percent fixative and 75 percent water. After the June spread of contamination, improvements included changing the mix to equal parts fixative and water.
The manufacturer does not recommend dilution, and no analysis was done to determine whether diluted fixative would perform well, the report said.
The report also found that management could have paid more attention to employee concerns and suggestions. Opportunities may have been missed to change some practices.
The CH2M report listed 42 steps to take in response to its findings. They ranged from changes to training for radiological workers to a technical engineering evaluation of how best to apply fixative.
The report is now in the hands of an expert panel assembled by the Department of Energy for feedback and possible revision.
Demolition has been stopped at the plant since December. A new demolition plan is being developed and improvements listed in the report will be implemented when demolition resumes, if the DOE expert panel agrees with them.
The improvements also are intended to guide CH2M as it tackles other high-hazard project, including the cleanup of the highly radioactive spill beneath the 324 Building just north of Richland.