The Idaho National Laboratory says the internal radiological dose received by 16 employees last November was within the Department of Energy's limits.
In a news release Wednesday, the INL said it did not expect any observable health effects from the doses the workers received on Nov. 8, 2011, during a planned fuel plate packaging operation inside the decommissioned Zero Power Physics Reactor at INL’s Materials and Fuels Complex.
According to the INL, workers were instructed to open a storage container called a “clamshell” and prepare the contents for shipment to another DOE facility. After removing four clamshells from storage, but before bringing them into the workroom for the operation, the workers noted that two of the clamshells had atypical labels indicating potential abnormalities with the fuel plates located inside. The immediate supervisor and the nuclear facility manager for the work were consulted, and a decision was made to proceed with the packaging operation. The four clamshells were then taken to the workroom and placed in a fume hood.
When the workers opened the first clamshell, they discovered that the fuel plate inside was wrapped in plastic and tape. While attempting to remove the wrapping material, there was an uncontrolled release and subsequent spread of radioactive contaminants in the workroom. This release resulted in an exposure of measurable levels of radioactive contamination to the workers, as well as to various facility structures, systems and components inside the ZPPR facility.
All of the affected workers returned to work the day after the accident, and all have been cleared to perform radiological work, INL said.
The lab will hold a news conference Thursday with more details.