Published online by Cambridge University Press: 03 September 2012
Wrought and cast low-carbon steel are candidate materials for the thick (e.g. 10 cm) outer barrier of nuclear waste packages being considered for use in the potential geological repository at Yucca Mountain. Dry oxidation is one potential degradation mode for these materials at the moderately elevated temperatures expected at the container surface, e.g. 323–533 K (50–260 °C). Therefore, numerical predictions of dry oxidation damage have been made based on experimental data for iron and low-carbon steel and the theory of parabolic oxidation. A numerical approach employing the Forward Euler method has been implemented to integrate the parabolic rate law for arbitrary, complex temperature histories. Assuming growth of a defect-free, adherent oxide, the surface penetration of a low-carbon steel barrier following 5000 years of exposure to a severe, but repository-relevant, temperature history is predicted to be only about 0.127 mm, less than 0.13% of the expected container thickness of 10 cm. Allowing the oxide to spall upon reaching a critical thickness increases the predicted metal penetration values, but degradation is still computed to be negligible. Based on these physically-based model calculations, dry oxidation is not expected to significantly degrade the performance of thick, corrosion allowance barriers constructed of low-carbon steel.