What is it about?
Several metallic materials have been proposed as corrosion-resistant barriers in geological repositories to provide containment to high-level nuclear waste. In this work, the different degradation modes for each type of metal/alloy proposed as a barrier are discussed. These degradation modes depend not only on the selected material but also on the environment in contact with the material. Selection of the host rock and design of the other engineering barriers will affect the performance of the nuclear waste container. The effects of the environmental and metallurgical variables on the degradation of the container are discussed.
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Why is it important?
Selection of a metallic material as a corrosion-resistant barrier for the waste container is intimately related to the engineered barrier system as a whole and with the previously selected host rock. The degradation mechanisms that are expected in each case depend on the selected material and the evolution of metallurgical and environmental conditions over time. Some degradation modes may be avoided or minimized by appropriate material or backfill selection. It is very important for the national programs of nuclear waste management to identify and assess the anticipated degradation modes of the selected materials in a time-evolving environment.
Perspectives
Carbon steel and oxygen-free copper are the most popular choices for corrosion-resistant barriers of high-level nuclear waste containers in saturated repositories. There is a trend to avoid or minimize the likelihood of any type of localized corrosion even at the expenses of having significant general corrosion rates, at least in the initial aerobic period. Generalized corrosion is much more easier to deal with in models and predictions than localized corrosion. However, passive materials which may be prone to crevice corrosion rather than pitting, such as titanium and nickel based alloys, are an interesting choice, though it is harder to predict the behavior of passive films over such long time scales.
Dr Martín A Rodríguez
Comision Nacional de Energia Atomica
Read the Original
This page is a summary of: Anticipated Degradation Modes of Metallic Engineered Barriers for High-Level Nuclear Waste Repositories, JOM, February 2014, Springer Science + Business Media,
DOI: 10.1007/s11837-014-0873-7.
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