ABSTRACTRadiation damage has been studied in natural rock salt from various localities, including potential repository sites. In the 100 to 300 C range the damage consists of point defects, primarily F-centers, and colloidal metal sodium particles. With increasing dose the F-centers grow to a saturation level, reached at 107 –108 rad, that decreases with increasing temperature to a negligible level at 300 C. Colloid concentration vs. irradiation-time curves follow nucleation and growth curves accurately described by C tn, or C(dose)n, relations at large irradiation times. For fourteen samples,n = 1.85± 0.18 but the values of C vary by a factor of more than 103. The constant C is related to the sample strain, the impurity and void content, dose rate, and possibly other factors. The currently available data indicate that rock salt adjacent to radioactive waste canisters, at a temperature of 150 C, will contain between 0.01 and 10 mole percent of sodium metal when the total dose reaches 1010 rad.