On September 1, 1994, subcontractors at the Mound Plant were contaminated while working on a potable water system upgrade construction project. The subcontractors penetrated a ceiling during a drilling operation and contaminated dust fell on several individuals. The workers skin was not contaminated and contaminated clothing was properly disposed of. Health physics personnel decontaminated the area and decontamination and decommissioning personnel suspended the project until an investigation team could determine the cause and corrective actions. (ORPS Report ALO-DA-EGGM-EGGMAT02-1994-0010)
Facility personnel have partially decontaminated and decommissioned the building and sealed the walls and ceiling to mitigate contamination. The construction project was to supply a new potable water system and was covered by a radiation work permit. Two subcontractors were in the ceiling crawl space in full personnel protective equipment. Two subcontractors on the floor were not wearing personnel protective equipment because special clothing was not required by the permit.
A health physics surveyor was monitoring the project and the four subcontractors were escorted by a security guard.
The subcontractors in the crawl space were drilling peripheral holes to cut out a four-inch diameter hole for the potable water piping to pass through when the ceiling was penetrated. Dust from the ceiling dropped through the holes and fell on the subcontractors below and also the health physics surveyor and security guard. Only the outer clothing and shoes of the four individuals on the ground were contaminated. Health physics personnel took skin and nose wipes as well as whole body counts from the four contaminated individuals. Health physics personnel took samples of the area determined that the contamination was from americium and plutonium.
This event underscores the need for personnel performing radiological work in older DOE facilities to be aware of and anticipate the possibility of encountering contamination when opening potentially contaminated areas. Many of these older facilities have a history of contamination still residing in the floors, walls, and ceilings that have been sealed.
Article 126 of DOE/EH-0256T, Radiological Control Manual, states: In performing assigned duties within radiological areas, workers should be familiar with the area radiological conditions and be aware of the possibility that changes may occur due to unforeseen reasons.