On the pH control at supercritical water-cooled reactor operating conditions

Application of LiOH(aq) for the pH control of the coolant at supercritical water-cooled reactor (SCWR) operating conditions is examined. The pH values of dilute aqueous LiOH solutions (c = 10−6–10−2 mol/kg) are calculated based on recently reported simulation data for the association constant of LiOH at supercritical water conditions [Plugatyr, A., Carvajal-Ortiz, R. A., Svishchev, I. M., 2011. Ion-pair association constant for LiOH in supercritical water. J. Chem. Eng. Data 56(9), 3637–3642]. The results indicate that at the operating pressure of the SCWR of 25 MPa, addition of LiOH to the coolant will provide adequate pH control for water densities above 0.17 g/cm3 (T < 400 °C). At densities below 0.17 g/cm3 the pH control becomes progressively more difficult as water density decreases. The results also suggest that the pH control via LiOH(aq) addition at densities below 0.086 g/cm3 (T > 514 °C) is, arguably, impractical as it requires operation at high concentrations of LiOH(aq).