A NEW GENERATION OF PASSIVE RADON MONITORS: THE FILM-BADGES FOR OCCUPATIONAL EXPOSURES

The passive radon monitors are typically formed by a radon-diffusion chamber, enclosing a track detector or an electret. Recently, new passive Rn monitors have been developed, which are similar to the neutron film badges. These badges present unique characteristics for the assessment of the occupational exposure to radon, such as compactness, fast-time response and any desired response sensitivity. Finally, these badges make it very easy to stop and to start the measurements, as required for assessment of the occupational exposures, which operations are very difficult, if not impossible, to achieve with existing monitors. These radon badges are based on the radon sorption by solid materials, namely plastics for radon absorption and activated carbon cloths for radon adsorption. Plastics may have a rubber-like (e.g. silicone) or a glass-like morphology (e.g. polycarbonate). The most interesting materials for these applications are the glass-like solids, the properties of which are expected to be little dependent on temperature. If radon badges with a large response sensitivity are desired, then adsorptive radiators formed by thin layers of activated carbon tissues are used. The key strategy, adopted for the radon film badges, was to use radiators into which radon diffuses rapidly, in order to ensure a fast-time response for radon monitoring. All the Rn film-badges, listed above, are formed by the same very compact device and may have response sensitivities, which may differ by several orders of magnitude.