A personal discriminating monitor for tritiated water vapor

A personal monitor for tritiated vapor in air based on scintillation is being developed by the Polytechnic of Milan and JRC of Ispra. A thin hygroscopic salt layer has been laid on the flat surface of a solid scintillator mounted inside the monitor. A small pump continuously supplies the monitor with filtered air samples taken from the room. The tritium oxide (HTO) in the air flow is reversibly trapped on the hygroscopic surface. A fraction of the beta particles emitted by tritium produces scintillation light in the solid scintillator which is detected by a miniaturized photomultiplier tube. The monitor can reveal HTO air contamination as low as 8×105 Bq m−3–which is one-tenth of the limit for workers – in a short time (150 s). Several tests have been performed to check instrument response linearity and delay, the sensitivity to tritium and gamma-rays and the influence of other parameters such as air flow rate, relative humidity, vibrations and shocks.