A Phenomenological Approach to Simulating the Evolution of Radioactive-Waste Container Damage Due to Pitting Corrosion

Abstract

RADIOACTIVE-WASTE CONTAINER DAMAGE DUE TO PITTING CORROSIONABSTRACT The damage to high-level radioactive-waste containers by pitting corrosion is an important design and performance assessment consideration. It is desirable to calculate the evolution of the pit depth distribution, not just the time required for initial penetration of the containers, so that the area available for advective or diffusive release of radionuclides through the container can be estimated. A phenomenological approach for computing the time evolution of these distributions is presented which combines elements of the deterministic and stochastic aspects of pit growth. The consistency of this approach with the mechanisms believed to control the evolution of the pit depth distribution is discussed. Qualitative comparisons of preliminary model predictions with a variety of experimental data from the literature are shown to be generally favorable. The sensitivity of the simulated distributions to changes in the input parameters is discussed. Finally, the results of the current model are compared to those of existing approaches based on extreme-value statistics, particularly regarding the extrapolation of laboratory data to large exposed surface areas.

Review of the Modelling of Corrosion Processes and Lifetime Prediction for HLW/SF Containers—Part 1: Process Models

“…Pitting of passive alloys [109][110][111] Addresses variability and uncertainty inherent to localised corrosion. Lack of mechanistic basis.…”

“…Henshall [109][110][111] described a stochastic-based model for predicting the initiation and growth of pits for the YMP, but the approach is broadly applicable to any container material in any type of repository. The probability of pit initiation and stifling, of pit growth and the resulting distribution in pit depths can all be predicted based on this stochastic treatment, provided there is suitable empirical input data.…”