Radiological survey of the Belgian upper part of the Meuse river during the triennial low water

Every three years, when the dams on the upper Meuse river are opened to allow heavy maintenance works on the sluices and banks, more extensive sampling campaigns are organised, taking advantage of the low water level. This particular situation facilitates sampling and, hence, provides the opportunity to enlarge the sample set and the sampled quantities. These triennial sampling campaigns have been performed regularly since 1968. The data collected during these periods have shown to be useful as guidence in the choice of the most relevant bio indicators used in the routine surveillance programme. By request of the Federal Agency for Nuclear Control (FANC), the sampling campaign has been reduced considerably in 2004, as the activity levels observed in previous years (1998 - 2001) proved to be very low in most of the compartments. Most of the measured samples remain below limits of detection.