Nuclear Waste Package Corrosion Behavior in the Proposed Yucca Mountain Repository

Abstract

AbstractThe corrosion performance of spent nuclear fuel waste packages is becoming increasingly important in establishing the viability of the proposed Yucca Mountain repository system. Current package concepts propose the use of a 2 cm thick nickel-base superalloy (Alloy 22) shell as the main barrier to prevent corrosion penetration over many thousands of years. The expected package service conditions, as well as their variability and uncertainty, are discussed. The electrochemical conditions known to be responsible for passive behavior and its breakdown in Alloy 22 and similar alloys are examined in the light of the predicted repository environment. Durability prediction approaches and their conclusions are considered. Efforts to determine the relative impact of localized modes of failure and uniform passive dissolution on package durability are reviewed, along with open issues in need of resolution and alternative package designs. The basic question of the validity of extrapolating corrosion behavior over many times the duration of the present base of experience is addressed.