On April 6, 1994, an employee at Rocky Flats Building 371 discovered radiological contamination on his shoes when he exited a radiologically controlled area. (ORPS RFO--EGGR-371OPS-1994-0034).
Investigators traced the source of contamination to one-square-meter on the floor near a glovebox in Building 371. They determined that the contamination was remnants of a spill that had been painted over to seal it. Clean-up personnel had painted the contaminated spot a magenta color to warn personnel of the fixed contamination underneath the single layer of paint. Maintenance personnel did not repaint the worn spot and the seal over the contamination was lost, allowing it to adhere to the bottom of the employee's shoes.
Radiological controls personnel at Rocky Flats decontaminated the area to an acceptable level and painted a layer of magenta over the spot. When that layer is dry, they will paint over the magenta layer with gray to match the remaining floor. As the top layer of gray is worn away, the underlying magenta will appear, indicating to maintenance personnel that a new coat of paint is required.
ONS personnel reviewed the occurrence reporting and processing system for similar occurrences and noted that many DOE facilities use paint to seal fixed contamination.
On May 15,1993, radiation protection technologists at the Rocky Flats Plutonium Processing and Handling facility discovered contamination while surveying Building 771 for contamination control. Investigators discovered that the contamination had escaped through worn paint on the floor. (ORPS Report RFO-EGGR--771OPS-1993- 0053)
On March 13, 1992, a radiation protection technologist at Rocky Flats Plutonium Processing and Handling facility discovered contamination on the bottom of his protective shoe covers while exit monitoring. Investigators determined that the contamination was bleeding through worn paint on the floor. (ORPS Report RFO--EGGR- 771OPS-1992-0034)
These events are significant because they illustrate that contamination can bleed through paint. DOE/EH-0256T, DOE Radiological Control Manual, article 222, section 2, states: "Surfaces exceeding the values of Table 2-2 for total contamination may be covered with a fixative coating to prevent the spread of contamination. However, reasonable efforts should be made to decontaminate an area before a coating is applied. A fixative coating shall not be applied without the approval of the Radiological Control Manager." Section 3 requires radiological surveys of areas where contamination seals may wear away over time. It also requires a formal inventory of fixed- contamination areas and posting of those areas. Section D requires removable contamination to be reduced to less than detectable levels before a fixative coating is applied. Fixed contamination should be covered with two layers of coatings of different colors. Additional coating should be applied when the bottom color appears.
Painting over fixed contamination on floors and walls is a common practice in the nuclear industry. Whenever fixed contamination is painted over, provisions should be made to alert personnel to the existence of contamination under the coating. Permanent plaques or sign postings may be effective. In older DOE facilities, where floors and walls may have been sealed several times, the potential for releasing contamination should be routinely considered when planning work activities that can disturb paint and sealants.