A real-time tritium monitor with an MPC proportional response to airborne mixtures of TH and THO

A fast response tritium-in-air monitor that can detect airborne HT and HTO in proportion to the occupational maximum permissible concentration (MPC) of either species has been deceloped at Lawrence Livermore Laboratory. The sample gas is selectively filtered through a dimethyl silicon membrane resulting in a throughput that is 400 times greater for HTO than for HT. After filtering, the tritium is detected in a 10 cm3 flow-through proportional counter. A short accumulation time, for a 5 s response to high levels of tritium (>= 1000 MPC), and a longer accumulation time, for a 60 s response to low levels of tritium (>= 10 MPC), are included. To avoid false alarms the short accumulation counter is continuously compared to a pulser set at three standard deviations above background. (orig.)