The use of passive detectors to monitor tritium on surfaces

Commercially available BeO exoelectron dosemeters and electret ion chambers (EICs) are being adapted and applied to in situ field monitoring of tritium on surfaces. Thin layer BeO on a conductive graphite substrate is of the order of 50 times more sensitive to tritium than the EIC. At the US department of Energy release limit for fixed surface tritium of 5000 dpm per 100 cm2, the exposure time for quantification with the exoelectron dosemeter is of the order of one hour. A multipoint Geiger counter was used for reading exoelectron emission. An alternative ceramic BeO dosemeter (Thermalox 995) has low electrical conductivity and will require a different reader to overcome problems of surface charging during exoemission. The electret is very easy to use and read. Its practical use will be for surfaces with relatively high levels of tritium contamination. (author)