Degradation Modes of Alloy 22 in Yucca Mountain Repository Conditions

Abstract

The nuclear waste package design for Yucca Mountain (Nevada, USA), in its current configuration, consists of a double wall cylindrical container fabricated using a highly corrosion resistant Ni-based Alloy 22 for the outer barrier and type 3 16 stainless steel for the inner structural vessel. A mailbox-shaped drip shield' fabricated primarily using Ti Grade 7 will cover the waste packages. The environmental degradation of the relevant materials have been extensively studied and modeled for over ten years. This paper reviews the state-of-the-art understanding of the degradation modes of Alloy 22 (N06022) due to its interaction with the predicted in-drift mountain conditions including temperature and types of electrolytes. Subjects discussed include thermal aging and phase stability, dry oxidation, general and localized corrosion, stress corrosion cracking and hydrogen induced cracking.

Pitting and General Corrosion Susceptibilities of Materials for High Level Radioactive Waste (HLW) Disposal

“…No studies were carried out on superaustenitic and nickel-based alloys. Other geological disposal concepts studying the corrosion behavior of Hastelloy C-series are difficult to compare because other pore-water properties were applied [39,40].…”