Boric Acid Ionization Constants and Triborate Formation Constants under PWR Primary Coolant Conditions by AC Conductivity

Abstract

Thermodynamic data for boric acid, borates and polyborates are needed to model the chemistry in fuel deposit crevices of pressurized water reactors under 'hideout' conditions that lead to crud-induced power shifts (CIPS, an operational issue), and for bulk PWR high temperature coolant chemistry. This paper reports boric acid ionization constants to 350 °C and preliminary results of a study aimed at measuring accurate triborate formation constants from 10 to 250 °C, using a unique high-precision flow-through AC conductance instrument. The results are being used to extend the database of the EPRI chemical modelling program MULTEQ to PWR primary coolant 'hideout' conditions.