Zeta potential measurement of magnetite in simulated primary PWR chemistry using streaming potential technique - T02-6

Deposition of corrosion products can result in several types of issues in the primary and secondary cycles of PWRs, e.g. activation build up, localized corrosion, reduced heat transfer. Several factors affect the deposition behaviour of corrosion particles in these environments. Surface charge, namely zeta potential, is suspected to be one of the factors affecting the deposition process. The best colloidal stability is achieved with greater absolute values of zeta potential, since the electrostatic repulsion between the charged particles increases. Correspondingly the particles tend to aggregate and deposit more when zeta potential values of two particles have opposite charges, or their charges approaches zero value. An improved measurement equipment based on streaming potential technique has been built at VTT and applied on zeta potential measurements in various simulated PWR environments. In this study, the zeta potential measurements on magnetite particles were performed up to ca. 250 C in simulated PWR primary side chemistry and the obtained values were compared to literature. The measurements were performed with and without magnetite to distinguish the effect of the filter on pressure difference. In a solution corresponding to the end-of cycle chemistry, the zeta potential values obtained were slightly negative at room temperature and approached zero as the temperature was increased above ca. 200 C. The results were compared to the ones available in literature, which were close in magnitude and followed similar trend as a function of temperature. In the beginning-of-cycle water chemistry, the measurements were not successful and thus additional measurements and improvements to the setup should be considered. (authors)