An excavator later found to have radioactive contamination was taken from the Hanford nuclear reservation to a Pasco shop for maintenance.
Workers at Powers Equipment in Pasco are not believed to have been put at risk, but some contaminated items were found there after the work was completed.
The problem was discovered Monday afternoon when the excavator was returned to Hanford, said Mark McKenna, spokesman for Washington Closure Hanford.
Radiological control technicians surveyed the excavator before it was put back into use and detected contamination in two places. They found radioactive contamination on the grease on the bucket joint and on grease on the turret deck, which pivots below the cab.
The contamination likely was spread in the grease from one part of the equipment to another, said Jerry Simiele, Washington Closure radiological control and industrial hygiene manager.
A crew was sent to Powers Equipment in Pasco, which had leased the excavator for Hanford use, to survey for any contamination there. The survey found no contamination in the equipment yard or public areas, but it did find three contaminated items.
A pin removed from the excavator arm and shims used to stabilize the pin were bagged and taken to Hanford. In addition, a coupler for hydraulic lines that was removed from the excavator and replaced also was found to have contaminated grease.
Because the coupler weighs several hundred pounds, work continued Tuesday to ship it to Hanford.
Levels of contamination found were low, and the health of Hanford or Powers Equipment workers was not at risk, Simiele said.
"The grease was working to our benefit," said Earl Fordham, the Washington State Department of Health's regional director of the Office of Radiation Protection. It did an independent survey of Powers Equipment Tuesday, confirming Washington Closure's findings.
The contamination would have had to be inhaled or ingested to harm workers, but it was trapped in the grease, said Fordham and Simiele. Fordham also agreed that levels of contamination were low.
Washington Closure also surveyed the trailer used to haul the excavator and found it was clean. The trailer had been taken to a Tri-City nursery before contamination on the excavator was discovered.
The Powers Equipment excavator was used by Washington Closure in the 300 Area just north of Richland until it was taken Sept. 26 back to Powers Equipment in Pasco for maintenance. It then was brought back to Hanford to dig up contaminated soil and waste burial sites near N Reactor.
Most excavators do not leave Hanford for maintenance work, said Cameron Hardy, DOE spokesman. But this was not one of the excavators used full time at Hanford, but one that had been leased from Powers Equipment by a Washington Closure subcontractor, he said.
Washington Closure surveys all items that come out of areas that require radiological controls, Simiele said.
But for a large piece of equipment like an excavator, that requires some disassembly to get to nooks and crannies where radiological material could be caught up, Simiele said. In this case, one of the pins that hold the bucket on likely was contaminated and that part of the excavator equipment was not taken apart and surveyed.
However, the equipment with the pin was disassembled when it arrived at the shop and the contamination then likely was exposed and spread, he said.
Washington Closure is reviewing its protocol for releasing equipment from the site. It's considering possibly adding independent radiological surveys of equipment to surveys now routinely conducted. It's also looking at standards for how much disassembly of the equipment should be done before it is surveyed.
"We just want to make sure we learn our lessons from this and look at procedures so it doesn't happen again," Hardy said.
Business continued Tuesday at Powers Equipment.
Co-owner Jim Powers said Washington Closure and other agencies handled the incident professionally and showed particular concern for the employees and the business.
-- Annette Cary: 582-1533; email@example.com