Impacts of cooling water quality on operational safety of water cooled components from CANDU reactor primary system

By operation in aqueous environment at high temperature and pressure, the structural materials from Primary Heat Transport System (PHTS) are covered with protective oxide films, which maintain the corrosion rate in admissible limits. The existing experience of different nuclear reactors shows that the water chemistry has an important role in maintaining the integrity of the protective oxide films. To investigate the influence of water chemistry (pH, O2 dissolved, Cl-, and F-) on corrosion of some structural materials (carbon and martensitic steel, Zr and Ni alloys) and to establish the maximum permissible values, corrosion experiments by static autoclaving and electrochemical methods were performed. The experimental results allowed us to establish the contribution of the water chemistry in initiation and evolution of some accelerated corrosion processes. (author)