Radioactive contamination was found outside a Plutonium Finishing Plant office trailer, after plant workers were relocated to that office and other offices farther from the plant.
Hanford officials responded by instituting stricter requirements for workers leaving the radiological control zone at the plant.
Careful surveys for radioactive contamination have been conducted at the central Hanford plant since a spread of radioactive contamination was discovered after the demolition of the most contaminated portion of the plant in mid December.
Officials have struggled to get the spread under control, with contamination found as recently as the past weekend on an employee car that had been parked at the plant for several weeks.
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Specks of radioactive contamination believed to have spread during open-air demolition have been found on surfaces, and airborne contaminants have been detected in air samples collected since late October through at least the end of December.
On Monday an instrument technician put on work boots at his office, which was outside the plant’s control area, and took a van into the control area. The control area is a wide area around the plant campus, where access is tightly controlled and no private vehicles are allowed.
The worker stopped to survey his clothing for any contamination before entering an area at the plant where radiological contamination is presumed to be present and precautions for it are taken.
He found contamination on his boot before entering the radiological control area.
The discovery triggered a survey of the van, the path he had walked and his office trailer, with workers there initially told to remain in place while surveys were conducted.
One spot of radioactive contamination was found on the steps into the office trailer, with all other areas clean.
In response, Hanford officials ordered all radiological surveys of workers leaving control areas of the plant to be surveyed by technicians, rather than allowing workers to survey themselves.
During the third week of January, workers were moved from a trailer village of offices at the plant to offices farther away.
Careful surveying for contamination kept finding radiation at the trailer village, but much of it was naturally occurring radiation, according to Hanford officials. Positive results were treated as a spread of radioactive contamination until it could be determined whether the radiation was from plutonium or other isotopes that might have spread from demolition at the plant or was due to radon.
On Monday new management was assigned to the plant to rebuild public and worker trust that the project was being safely managed. CH2M Hill Plateau Remediation Co. was replaced by its parent company, Jacobs Engineering Group.
Only work to contain contamination and keep it from spreading is now being done at the plant.