Investigation and reduction of personnel exposure levels in Bavarian water supply facilities

摘要

Since 2001, the protection against natural radiation is implemented in German law. The limit of the annual effective dose is 20 mSv. But the annual effective dose due to radon exposure is only limited at certain work places, e.g., mines and water supply facilities. The federal states are responsible for the observation of this law. Consequently, all Bavarian water supply facilities were investigated with regard to radon concentrations in indoor air as well as radon exposure of the staff working in these buildings. In 0.7% of all water supply facilities, the staff were exposed to levels that exceed the limit of 20 mSv/a. In 1.7% of the water supply facilities, the personnel exposure level was between 6 and 20 mSv/a. There are several remedial actions that have proven to be successful: it is inexpensive to reduce the radon exposure by reducing the time spent in the units; and the buildings can be ventilated with stationary or mobile devices by blowing fresh air directly to the working place. In one case, a combination of an effective ventilation system with a separating wall between the water purification basins and the water supply control centre reduced the annual effective dose of the process controller from 100 to about 6 mSv.