Measurements of Residual Tritium in the Exhaust System of a Former Tritium Research Laboratory
L. E. Wahl, J. A. Jelinski
Although the former National Tritium Labeling Facility (NTLF) at Lawrence Berkeley National Laboratory (LBNL) has been closed and cleaned out, very low levels of tritiated water are present in the effluent air. This tritium most likely is due to the gradual release of residual tritium from the walls, ceilings, and floors of the empty laboratories and from the internal surfaces of the exhaust systems. To quantify the release of residual tritium in the exhaust system of one of the empty laboratories, a comparison was made between two stack-sampling locations about 40 m apart on the 75-m-long duct that exhausts a laboratory in the former NTLF. One sampling location, on the horizontal section of duct, is on the roof of the former NTLF. This is the historical sampling location. The second location, about 40 m downstream from the rooftop site, is on the vertical stack located on the hillside behind the former NTLF. This is a new sampling location. Samples were collected from both sites for four consecutive weeks. Quality control data were also obtained from weekly sample flow rate checks, weekly leak tests, and one split-sample analysis. The data indicate that, on average, twice as much tritium was measured at the hillside site than at the rooftop site. The residual tritium in the 40-m section of stack between the rooftop and hillside sites averaged 13.1 MBq wk1 (6.81 × 102 MBq yr1). Doses estimated using CAP88-PC, Version 2, indicate that this additional amount of tritium does not contribute significantly to the annual effective dose equivalent received by the maximally exposed individual. Based on these results, sampling will continue at the hillside site, and results will be assessed to determine whether sampling at the rooftop site should be discontinued and whether sampling should continue permanently at the hillside site.
This abstract was presented at the 37th Annual Midyear Meeting, "Air Monitoring and Internal Dosimetry", Effluent and Environmental Monitoring Session, 2/8/2004 - 2/11/2004, held in Augusta, GA.