Notifiable work activities in water supply facilities – execution experience from Bavaria

Since 2001, the protection against natural radiation is implemented in the German Radiation Protection Ordinance. Water supply facilities are now obliged to estimate the radon exposure of their staff. In 75 water supply facilities in Bavaria, Germany, radon exposures above the action limit of 6 mSv per year were determined. In these facilities the radon exposure has to be continuously monitored. By the proposal of the Bavarian Environment Agency (LfU), this should be done by continuous wearing of personal track-etch detectors, that are changed every three months. The results are sent to the LfU and reported to the central German dose register. Because of measuring periods of three months a high radon exposure that could probably exceed the annual limit of 20 mSv can be recognised at an early stage and immediate protection measures can be taken. In collaboration with the University of Regensburg remedial strategies for the permanent reduction of the radon exposure have been developed. The exposure is effectively reduced by reducing the time spent inside the units as much as possible. A very effective way to reduce the radon concentration inside buildings and hence the radon exposure is to blow fresh air directly into the work place of the staff with stationary or mobile devices. An alternative way to reduce the indoor air concentration is to avoid any transfer of radon polluted air exhausted from purification tanks to indoor air. For a long lasting success of the remedial measures a work instruction was developed by the LfU. All plants, their mean radon concentration and the measures to be taken have to be stated there.