THE EFFECT OF GEOLOGICAL PARAMETERS ON RADIATION-DAMAGE IN ROCK-SALT - APPLICATION TO ROCK-SALT REPOSITORIES

Laboratory irradiations at a constant dose rate of 15 kGy/h at 100 deg rees C have enabled the study of the radiation damage in several types of rock salt. Total doses ranged from 20 kGy to 48.9 MGy. Two methods (optical absorption and release of hydrogen by reaction with water) h ave been used to measure the concentration of radiation-induced defect s. Their concentration was compared with the dose and the chemical and mineral composition of rock salt samples, using multivariate statisti cal techniques. The results show a loglinear increase in the concentra tion of colloidal sodium with dose, whereas the F-centers concentratio n remains nearly constant. Moreover, there is a clear influence of the mineral composition of the rock salt in the radiation damage, leading to defect concentrations varying over one order of magnitude for the same dose. Rock salt with small amounts of accessory minerals presents the lo west defect concentration. Experimental data have been compare d with the theoretical predictions obtained by the Jain-Lidiard model. For doses higher than 1 MGy, both values are of the same order of mag nitude.