The Solubility of Magnetite and Nickel Ferrite Under Supercritical Water Reactor Coolant Conditions

Abstract

Experimental data for the solubility of magnetite, hematite, nickel oxide and nickel ferrite, which are limited to temperatures below 300 degrees C and 10 MPa, have been critically evaluated. The results were used to construct a thermodynamic model for the solubility and hydrolysis of magnetite and nickel ferrite suitable for calculating oxide dissolution and transport in sub-critical and super-critical water (250-450 degrees C 25 MPa). Our analysis shows that the iron (III) species, Fe(OH)4-, plays a particularly important role, and that both LiOH and ammonia have the potential to maintain pH in supercritical-water-cooled reactor coolants up to 400 °C. Shortfalls in the database, and experimental approaches to address these issues, are identified.