Analyses of Free Span Oxide Layers on SG Tubes of NPP Temelin

The differences in deposit layers on steam generator (SG) tubes of WWER NPP Temelin have been observed, namely in compactness and adhesiveness. The samples of the oxide layers have been taken from different SG during outage of the two units and analyzed. Results of the analyses are compared to previous results on deposit layers created during operation of SG model. The model simulates secondary side of SG tubes operation; the original feed water from the NPP Temelin has been used for tests. Deposit built up on tubes inside the model on the free surface is related to the real SG tube deposits and differences of the oxide layer morphologies are discussed.