Aqueous Sodium Phosphate Hideout Reactions With Nickel and Titanium Oxides Under CANDU-PHW ​Boiler Conditions

Abstract

Phosphate methods of chemistry control are widely used in thermal power stations and less widely in nuclear stations because of concerns about metal-phosphate "hideout" reactions. In this work, nickel phosphate and titanium phosphate hideout products that can form under CANDU-PHW reactor conditions have been synthesized using hydrothermal methods. The pure crystalline solids that were obtained have been characterised by Raman spectroscopy, ICP and FTIR and XRD. Two different solid phases were obtained from the synthesis with nickel oxide while one solid phase was obtained from titanium oxide. Solubility studies were carried out for the sodium titanium phosphate product. The results were used to derive thermodynamic models for the interaction of metal oxides with high temperature aqueous sodium phosphates. The thermochemical constants for the hideout reaction products are consistent with the geochemical thermodynamic database SUPCRT92 and other data bases used to model corrosion product behaviour.