On April 7, 1993, personnel at the Los Alamos TA55 Plutonium Process and Handling facility detected an alarming continuous air monitor in room 205, indicating the presence of potentially hazardous levels of airborne radioactivity. Further investigation determined that the continuous air monitor was activated by the presence of transuranic airborne contamination. Facility personnel report that the airborne contamination apparently resulted from the evaporation of contaminated seal water that leaked from the pump shaft packing in the room Wet-Vac system. Facility personnel do not know the exact time that the alarm actuated because the continuous air monitor in this normally unoccupied room is not connected to the TA- 55 operations center.
After notification of the alarm, a facility radiation control technician removed the continuous air monitor filter for monitoring. The technician measured 750 disintegrations per minute on the filter, indicating airborne contamination. The radiation control technician subsequently detected contamination on and under some of the components of the Wet-Vac system in the room. Measurements indicated 2,000,000 disintegrations per minute per 100 centimeter-squared direct alpha contamination on the pump. The radiation control technician then taped and marked doors to the room with warnings not to enter unless respiratory protection was worn. Facility personnel tightened the pump seal and no further airborne radioactivity was noted. (ORPS Report ALO-LA-LANL-TA55-1993-0010)
The Office of Nuclear Safety has not yet been able to establish why or how long this condition existed, or if there have been previous problems with airborne contamination from the Wet-Vac system. It is also unknown at this time whether the Wet-Vac pump seals were part of the facility preventive maintenance program. The corrective actions and lessons learned developed by the facility as a result of the incident investigation may be provided in a future Operating Experience Weekly Summary update.