Determination of the physicochemical properties of boric acid for VVER emergency modes

Abstract The results of experimental research of physicochemical properties of water solutions of H3BO3 are presented in this article. The literature review about the influence of hydrogen ion exponent of H3BO3 solutions on its heat and mass transfer, and corrosiveness of an acid in the VVER reactor core in is given. It is found that the existing data does not cover the entire range of parameters (acid concentration, temperature and pressure) characteristic of a possible Loss-of-Coolant Accident (LOCA) at nuclear power plant with a VVER. The problem of the accumulation and crystallization of boric acid in case of LOCA and the operation of passive safety systems (such as hydro accumulators of the first, second and third stages, and a passive heat removal system) is formulated. Test equipment and techniques of research are described. The generalizing equations for the pH and acidity constant of hydrous solutions of H3BO3 in range of the concentration (5-100 gkg−1 H2O) and temperature (25-50 °C) has been obtained.