Characterization of the surface charge of oxide particles of PWR primary water circuits from 5 to 320 °C

The point of zero charge of three typical oxides found as colloids in PWR primary circuits has been measured by mass titration in a large range of temperature: from 5 to 320 °C for magnetite and cobalt ferrite, from 5 to 125 °C for nickel ferrite. Comparisons with zetametry were performed near room temperature. The protonation thermodynamic constants have been calculated. The standard protonation enthalpy at 298 K is −27 ± 5, −31 ± 6 and −32 ± 7 kJ mol−1, for the three oxides respectively. The sign of the surface charge of these colloidal particles in the temperature conditions of the primary circuit indicates that their adhesion onto the materials of the circuit is favored.