Borehole radar performance on fracture zone characterisation in crystalline bedrock

Borehole radar is, together with reflection seismic investigations one of scarce available methods for investigating the bedrock properties at further range than immediate borehole surroundings. In crystalline bedrock characterization project for disposal of the spent nuclear hel, the borehole radar measurements have been used mainly for investigation of orientation of the fracture zones and their extent from the borehole. Detailed and reliable information is required in this task. Radar method is relatively fast to be implemented and interpreted. Fractures and fracture zones, and their location, orientation, continuity and properties have been attempted to be assessed from the results. The bedrock properties that relate to radar reflections were assessed in detail by comparing reflections to other available borehole data. Comparison of data sets from different scales of observation has not been always a straightfonvard task. Better understanding of the radar method will allow more efficient use of the results.