ABSTRACTWrought 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.