Reconstruction of gamma dose distribution in salt at radioactive waste disposal site by the water insoluble fraction

Since 1968 the GSF has been carrying out research and development programmes for the final disposal of high activity waste in salt mines. The long term stability of the rock salt formations is assessed, by simulation of heat-producing waste by means of electrical heater and 60Co sources. After the termination of the simulation experiment, vertical and horizontal gamma dose profiles in the rock salt are determined by using the natural rock salt as dosemeters. At the initial stage the thermoluminescence and lyoluminescence properties of rock salt were investigated and found not to be suitable for the dose reconstruction due to inhomogeneity of the salt. However, the water insoluble fraction of the rock salt as found to have more favourable TL dosimetric properties to measure absorbed doses up to 5 x 103 Gy. It is proposed that the method be used for regular check-ups at salt mines used as radioactive waste disposal sites. (author)