Recent efforts to identify methods of modeling pitting corrosion damage of high-level radioactive-waste containers are described. The need to develop models that can provide information useful to higher level system performance assessment models is emphasized, and examples of i,ow this could be accomplished are described. Work to date has focused upon physically-bas_'t phenomenological stochastic models of pit initiation and growth.These models may provide a way to distill information from mechanistic theories in a way that provides the necessary information to the less detailed performance assessment models. Monte Carlo implementations of the stochastic theory have resulted in simulations that are, at least qualitatively, consistent with a wide variety of experimental data. The effects of environment on pitting corrosion have been included in the model using a set of simple phenomenological equations relating the parameters of the stochastic model to key environmental variables. The results suggest that stochastic models might be useful for extrapolating accelerated test data and for predicting the effects of changes in the environment on pit initiation and growth.Preliminary ideas for integrating pitting models with performance assessment lt 'lt, models are discussed. These ideas include improving the concept of container "failure",• and the use of "rules-of-thumb" to take information from the detailed process models and provide ,,_to the higher level system and subsystem models. Finally, directions for future .... , r-,4-" ',L: '_Yr_

The materials selections described in this report are the culmination of many years of effort. W. G. Halsey was principally responsible for development of the selection criteria. R. D. McCdght contributed considerable personal ins_ght into the corrosion behavior of materials, led the Metal Barriers effort, and wrote an earlier, brief version of this report. G. E. Gdowski was responsible for much of the degradation. mode survey work. W. L. Clarke, Jr., contributed insights from years of experience with materials in the nuclear power industry, and leads the Corrosion & Electrochemical Processes Section of the Materials Division of the Chemistry and Materials Science • Department at Lawrence Livermore National Laboratory as well as serving as Technical Project Offk;er for LLNL participation in the Yucca Mountain Site Characterization Project. R. A. Van Konynenburg contributed in the areas of radiation effects and carbon-14 release, and edited this report.

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This cost estimate furnished by the Joseph Oat Corporation was to the best of _ knowledge obtained in accordance with the specification for use in making production cost estimates of high level nuclear waste containers and. internals for the Yucca Mountain Project, Ray. 2, and the Qualicy Program outline for Yucca Mountain Project-High Lavel Nuclear Waste Container Fabrication Cost Estimate _ali_v Assurance specified in B&g P.O.