A study was conducted to investigate the possible changes in brine chemistry and alkalinity in a highlevel nuclear waste salt repository caused by the interaction of brine with gamma-irradiated host rock. The technique employed involves measurements of the pH and total base in solution of brines made from rock salt irradiated to doses between 107 and 1010 rad under various environmental conditions. The results show that the pH and total base of the brines increase with increasing irradiation of the parent rock salt. Rock salt samples, irradiated in the dry condition at 40°C, produce brines with pH and total base values that increase from 7.25 pH units and 0.14 microequivalent/gram (µeq/g) to upper limits of 9.25 pH units and 1.2 µeq/g, respectively. Samples, irradiated dry at 125 °C, produce brines with pH and total base values that increase to 9.60 pH units and 35 µeq/g, respectively. The increase in total base in the aforementioned brines is indicative of F-center formation (at 40°C) and sodium-colloid formation (at 125°C) in the salt. Saturated brines irradiated in the presence of rock salt at 125 °C, however, became progressively more acidic while brines made from the adjacent rock salt became increasingly basic. With respect to the high and low pH brines that may be adjacent to waste packages, corrosion resistance of metal containers and the leachability of the waste form may be compromised. Additional data will be required to quantify the behavior of these components under anticipated repository conditions.