Both concentrated and dilute simulated solutions of saturated J13 and unsaturated UZ pore water were concentrated through distillation of the solutions under atmospheric pressure. It was observed that condensed vapors from the pH of J13 waters steadily rose during the distillations to a value of 10, while the pH of UZ waters remained steady until 90% of the volume of the solution had been distilled, after which the pH of the condensed vapors dropped precipitously, often below 1. Residual solutions analyzed when most of the solution had been distilled away were also found to be extremely acidic. The temperature of these residual solutions was around 144°C due to their high solute content causing boiling point elevation. All experiments were performed with the condenser open to ambient air at atmospheric pressure. The pH drop during the distillation of UZ water is attributed largely to the presence of large amounts of magnesium. Specimens of Alloy 22 tested in the residual solutions of at their boiling temperature (around 144°C) showed significant rates of general corrosion over a broad range, often approaching 1 mm/year. Similarly high corrosion rates were also observed in tests on Alloy 22 specimens in condensates obtained during the late stages of the distillation. These tests were performed either in situ at 75–80°C using a Soxhlet extractor, or in separate pressure vessels at temperatures between 90 and 130°C.