Oxidation kinetics and spallation of oxide film of the structural metal in helium under thermal cycles

The compositional change in corrosion product spalled during oxidation in the simulated HTR coolant under temperature cycling was examined by activation analysis. Comparison of three heats with different Mn, Al, Si and Co content, which influenced the behaviour of the materials significantly, susceptibility to intergranular attack suppressed to release of the radioactive products. Close relation was also found between the chemical composition of oxide film and the corrosion resistance. A special reference was made to the essential factors that control the rate of total release of Co into the environment system. (author)