The Evaluation of the Primary Circuit Passivation Layer Formed After Hot Functional Tests at the EMO3

The presented article outlines and describes the processes involved in the creation and testing of the passivation layer that was created during hot functional tests (HFTs) at the third unit of the nuclear power plant (NPP) Mochovce. The article is divided into several sections. In Sec. 1 is the description of the hot tests on the third block, in particular the chemical regime, i.e., the formation of hydrogen or the necessary adjustment of the pH value. Sec. 2 of the article describes the evaluation of the passivation layer using instrumental techniques, i.e., Raman microscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy. The results obtained by using these techniques provided a comprehensive view of the resulting layer and clearly defined its' structure. The measurement revealed that a passivation layer was formed, the inner layer of which is enriched with a chrome element. The upper part of the passivation layer was composed of iron oxides, mainly magnetite.