The Effect of Geological Parameters on Radiation Damage in Rock Salt: Application to Rock Salt Repositories

Abstract

Laboratory irradiations at a constant dose rate of 15 kGy/h at 100°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) have been used to measure the concentration of radiation-induced defects. Their concentration was compared with the dose and the chemical and mineral composition of rock salt samples, using multivariate statistical techniques. The results show a loglinear increase in the concentration of colloidal sodium with dose, whereas the F-centers concentration 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 lowest defect concentration. Experimental data have been compared with the theoretical predictions obtained by the Jain-Lidiard model. For doses higher than 1 MGy, both values are of the same order of magnitude.