Incorporation of 'corrosion-time' and effects of corrosion-product spalling in waste package degradation simulation in the potential repository at yucca mountain

摘要

A two-layer waste package (carbon-steel outer bawrrier and Alloy 825 inner barrier) is specified to dispose of high-level nuclear waste at the potential repository at Yucca Mountain. A set of imporvements and more realism have been added to a stochastic waste-package degradation model which was developed for a recent total system performanc eassessment of the potential repository [1]. The waste-package surface is divided into "patches" to better represent the general corrosion of the carbon-steel outer barrier. The "corrosion-time" concept is developed to represent the corrosion of the carbon-steel ourter barrier in changing exposure conditions with time such as those expected in the potential repository. With the patches approach and the corrosion-time concept implemented into the waste-package eegradation model, sensitivity of hte waste package degradation (failure and pitting degradation) to different threshold spalling thicknesses of the corrosion products from the carbon steel outer barrier is analyzed. The results show that the waste-package pitting degradation is sensitive to the corrosion-products spalling thickness of the carbon-steel outer barrier. A greater pitting degradation fot he waste packages is predicted with a smaller spalling thickness. Further understanding of the corrosion-products spaling in different exposure conditions (i.e., water chemistry, water contact mode, etc.) and its effects on carbon steel corrosion is needed to enhance the confidence in the waste-package performance modeling in the potential repository.