A Critical Evaluation of Boric Acid Thermodynamics in High-Temperature Water: A Revised Thermodynamic Model for Pressurized Water Reactor Applications

This paper reports a critical evaluation of high-temperature boron thermodynamic data, with a focus on pressurized water reactor (PWR) applications. The thermodynamics for aqueous borate and polyborate species implemented in most computer codes have been largely based on potentiometric data measured between 50 and 200 °C at Oak Ridge National Laboratory in the early 1970s. Recently, the dataset has been extended down to 10 °C and up to 350 °C as part of an EPRI-funded comprehensive experimental study by the University of Guelph (2016–2023). This paper reports a critical review and evaluation of high-temperature thermodynamic data for polyborate speciation, boric acid species volatility, and metal alkali borates solubility to provide the basis of a revised thermodynamic model for boric acid chemistry in high-temperature water. The revised model improves the ability to simulate the chemistry that takes place in PWR primary systems.