A feasibility study for the application of zinc injection into the primary coolant of the Korean PWRs

Zinc has the ability of incorporating into the spinel oxide layers building very stable and adherent oxide layers. Zinc containing spinel oxide layers are more tight and thinner than the magnetite or nickel ferrite layers. Zinc occupies these spinel oxide layers' empty boundary lattice sites and prevents or inhibits the diffusion mechanism of other cations through the oxide layers. This leads to improved protection of the metal surfaces against coolant exposure resulting in not only less metal release and corrosion rates but also in preventing the incorporation of fresh radiocobalt. Zinc injection of the boiling water reactor (BWR) or pressurized water reactor (PWR) coolant system is now technically and economically feasible for mitigating dose rate and primary water stress corrosion cracking (PWSCC). The object of this study is to present a summary of the results and conclusions of the operating experience obtained at all PWRs implementing adding zinc, and also to develop the requirements and criteria for a zinc injection demonstration program in Korea. (author)