Maintenance of the primary and secondary circuit chemistry - The key of the minimum corrosion of metallic components

The objective of this paper is the presentation of some chemistry regimes available in primary and secondary circuit of a CANDU Nuclear Power Station simultaneously with the establishment of some correlations between the corrosion behavior of some representative metallic materials and the specific parameters of the respective aqueous environments. First we reviewed the main chemical parameters of the aqueous environments from the primary and secondary circuit in a CANDU NPS and finally we established some correlations between these chemistry variations and the quality of superficial films formed on some representative alloys such as zirconium alloys and carbon steels from primary and secondary circuit, respectively. To characterize the filmed samples the following methods were used: the gravimetric, X-rays diffraction, metallographic microscopy method and some electrochemical methods such as: potentiodynamic and electrochemical impedance spectroscopy. Using these methods, there were established the corrosion kinetics and the characteristics of the films formed on the samples in the NPS operation conditions