RICHLAND – Workers at the Hanford nuclear reservation’s C Tank Farm were evacuated and other workers were ordered to take cover Wednesday night after an unusual radiation reading was detected near Tank C-101.
Thursday morning the Department of Energy said a transfer system may have leaked radioactive waste.
The radiation was detected near a sluice box, which holds equipment for the system used to spray liquid to help remove waste within Tank C-101, a 530,000-gallon capacity underground tank.
Liquid already contaminated with radioactive waste is used rather than water to prevent the creation of more waste.
Workers were evacuated from the C Tank Farm, a group of 16 underground tanks, after the radiation was detected at 9:35 p.m.
No contamination was found on any workers, but four workers were sent to Kadlec Regional Medical Center in Richland as a precaution. They have been checked and cleared to return to work.
Other workers were ordered to take shelter. That included workers in the 200 Areas in central Hanford and nearby and those near the K Reactors along the Columbia River.
Access to the entire nuclear reservation also was restricted.
Surveys first were conducted around the perimeter of the C Tank Farm and no unexpected radiological or chemical contamination was found, said Department of Energy spokeswoman Carrie Meyer.
The take cover order was lifted for all workers at 12:35 a.m. Thursday except workers in the 200 East Area, which includes the C Tank Farm, and at the nearby vitrification plant.
At 3:52 a.m. five workers entered the C Tank Farm to check for radiation near the Tank C-101 sluice box. The team included two firefighters, a nuclear chemical operator, an industrial hygiene technician and a health physics technician, according to DOE.
The team found no visible sign of a leak but again detected radiation on the shield box, although at lower levels than the night before.
The team applied a fixative to a 3-square-foot area to prevent the spread of any potential contamination.
Barricades were installed around the C Tank Farm, and the order for workers to take cover in the rest of the 200 East Area and the vit plant was lifted. Workers were told to return to work as usual for the Thursday day shift.
Hanford was under an “alert,” the lowest level emergency DOE declares, from 9:35 p.m. Wednesday until about 5 a.m. Thursday.
DOE protocol calls for an alert to be issued if there is liquid waste on the ground from a leak from a waste transfer system, either because the waste is visible on the ground or increased beta radiation rates are detected.
The Washington state Department of Ecology is following up to learn more about the leak.