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In an attempt to investigate Cs-Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel, Cs-Te corrosion out-pile tests of two 9Cr steels with different distributions of chromium carbide were carried out at 975K for 100h and their corrosion depths were compared. The corrosion is obviously more advanced in a specimen which has grain boundary carbide than in the one that doesn't. A considerable reason of the result is that the carbide distributed at grain boundaries promoted the corrosion reaction and the corrosion extended along the grain boundary. This is the first case in which the Cs-Te corrosion depth dependence on distribution of chromium carbide precipitation in Fe-Cr steel is clarified experimentally.

The corrosion behavior of Hastelloy-N alloys in molten salt coolant containing fission product elements were investigated to determine the safety of structural materials in molten-salt reactors (MSR). Corrosion tests of Hastelloy-N in the molten fluoride salt FLiNaK in an alumina crucible and a graphite crucible under argon gas were performed at 773 to 873 K for 100 h. In the experimental condition of this study, no synergistic effect of Cs addition in molten fluoride salt were observed on the corrosion behavior of Hastelloy-N immersed in molten fluoride salt. At 773K, no effect of Te addition in molten fluoride salt could be seen. With increasing test temperature, the depth of corrosive attack increased and depletion of Ni occurred. At 873K, the Ni-Te compound layer was formed on the corroded surface of Hastelloy-N immersed in the mixture of molten fluoride salt with Te in graphite crucible. It was estimated that the formation of Ni-Te compound layer depend on electrical potential of molten fluoride salt.