Co build-up in oxide layers on stainless steel under BWR-conditions with and without the influence of zinc

摘要

In light water reactors (LWR), small amounts of zinc are currently added to the reactor coolant to reduce radiation fields due to build-up of Co-58 and Co-60 in oxide layers on stainless steel. In this work, the diffusion of the Cobalt ions into the oxide layers under BWR conditions with and without zinc has been investigated using SIMS depth profiling analysis technique. Additional analysis methods such as electrochemical impedance spectroscopy, photo electrochemistry and the Mott-Schottky analysis were employed in order to assess the influence of zinc ions on the oxide structure, composition, semiconductor properties and growth kinetics. This combination allows the quantitative determination of the Cobalt diffusion rate, the relative composition, density and thickness of the built-up oxide. The correlation between Cobalt build-up and oxide growth is discussed in relation with zinc prevention mechanism.