ABSTRACT
OBJECTIVE: We report on (133)Xe contamination found in the reusable internal bacteria filter of our xenon ventilation system. METHODS: Internal bacteria filters (n = 6) were evaluated after approximately 1 mo of normal use. The ventilation system was evacuated twice to eliminate (133)Xe in the system before removal of the filter. Upon removal, the filter was monitored using a survey meter with an energy-compensated probe and was imaged on a scintillation camera. The filter was monitored and imaged over several days and was stored in a fume hood. RESULTS: Estimated (133)Xe activity in each filter immediately after removal ranged from 132 to 2,035 kBq (3.6-55.0 micro Ci), based on imaging. Initial surface radiation levels ranged from 0.4 to 4.5 micro Sv/h (0.04-0.45 mrem/h). The (133)Xe activity did not readily leave the filter over time (i.e., time to reach half the counts of the initial decay-corrected image ranged from <6 to >72 h). The majority of the image counts (approximately 70%) were seen in 2 distinctive areas in the filter. They corresponded to sites where the manufacturer used polyurethane adhesive to attach the fiberglass filter medium to the filter housing. CONCLUSION: (133)Xe contamination within the reusable internal bacteria filter of our ventilation system was easily detected by a survey meter and imaging. Although initial activities and surface radiation levels were low, radiation safety practices would dictate that a (133)Xe-contaminated bacteria filter be stored preferably in a fume hood until it cannot be distinguished from background before autoclaving or disposal.
