On April 27, 1994, a worker at Rocky Flats Solid Waste Treatment facility caused a combo self monitor to alarm when he exited a radiation area, in Building 776. Radiological controls personnel surveyed the area where the worker had been and discovered alpha contamination of 24,000 dpm inside a crack on the floor of room 127 of Building 776. As a precautionary measure, the radiation control technician foreman ordered nasal smears be taken from all personnel who had entered room 127 that day. Four persons may have received minor amounts of contamination, but results of the follow-up bioassay are not yet known. (ORPS Report EGGR-SOLIDWST-1994-0034)
Room 127 is a low level radiation storage facility, that workers commonly use as a passage to an adjacent room. Upon discovery of the contamination, radiation control technicians posted the room to require respiratory protection for entry. They identified the source of the contamination and surveyed rooms 127, 141, and 430 to discover any spread of contamination. They found a small amount of contamination in room 141 and removed it immediately.
Investigators determined that the contamination accumulated within the crack on the floor a long time ago and that it had been contained by paint or sealer that wore off, allowing the contamination to spread.
Radiation Control Technicians contained the contamination by covering it with cardboard and a plastic tape wrap, after which they removed the respirator requirement for room 127. They will decontaminate the crack by removing any surface contamination then sealing it with paint.
NS reviewed the occurrence reporting and processing system for similar incidents and found the following reports.
In Operating Experience Weekly Summary 93-36, ONS reported an event that occurred on August 30, 1993, at the TA-55 plutonium processing facility at Los Alamos National Laboratory where three workers received internal plutonium contamination while preparing equipment for decontamination and decommissioning. The three and ten other individuals in the room were evacuated when a continuous air monitor alarmed. The Occurrence Reporting and Processing System notification report stated that, after the evacuation, radiological control technicians wearing self contained breathing apparatuses entered the room to retrieve the monitor air filters. However, facility personnel reported in the ten-day report that the initial entry was made with full-face respirators, which do not provide the same level of protection as SCBAs. Subsequent analysis of the filters indicated that contamination levels warranted the use of SCBAs. (ORPS Report ALO-LA- LANL-TA55-1993-0033)
On July 25, 1991, at the Savannah River HB-Line facility five workers were contaminated when an operator opened an empty plutonium-238 shipping container. The container was not labeled to indicate that the interior was contaminated. One of the five workers received a committed effective dose equivalent to 16 rem. The four other individuals received uptakes resulting in committed effective dose equivalents ranging from 0.035 to 0.9 rem. (ORPS Report SR--WSRC-HBLINE-1991-1013)
These events underscore the need for radiological control personnel to take conservative measures to protect personnel when they are in areas with surface contamination that can be stirred, resulting in airborne contamination. To provide the greatest level of personnel safety, controls should require respiratory protection commensurate with the maximum possible radioactivity for entry into known areas of contamination or areas with a potential for airborne contamination. (Tom Chota -RPI (301) 540-2396)