Invited Paper AP+AS-TuM1
Development of Atom Probe Tomography for Studying Nuclear Corrosion Issues

Tuesday, October 20, 2015, 8:00 am, Room 211D

Material degradation and corrosion create significant challenges to nuclear energy production, both in terms of the structural integrity of plant components and also in the long-term disposal of high-level radioactive waste. For structural materials, stress corrosion cracking (SCC) continues to be a prominent issue for Ni-base alloys in the high temperature (~320 °C in pressurized water reactors) corrosive reactor environment. Despite decades of research, there has yet to be a consensus on the fundamental mechanisms that control SCC response. On the other hand, the long-term disposition of high-level nuclear waste generated by nuclear energy production continues to be an open question. Vitrification of high-level waste into a relatively stable form (e.g. borosilicate glass) is being actively pursued. However, disagreement exists about the long-term stability of the glass if/when exposed to ground water in a geologic repository due to an ill-defined rate-limiting process controlling glass dissolution. In both cases, high-resolution microscopy techniques including atom probe tomography (APT) provide unique opportunities to test various mechanistic theories with unprecedented spatial resolution and chemical sensitivity. Such studies have only recently been made possible through the advancement of site-specific focused ion beam (FIB) sample preparation methods and pulsed-laser APT systems, creating a unique environment for revolutionary discoveries.

In this talk, I will discuss the development of APT methods for characterizing SCC microstructures in select model and commercial alloys and also for characterizing the dissolution of model vitrified nuclear waste glasses. The corrosion of metals and the dissolution of glass present unique but overlapping challenges in sample preparation, data acquisition and data interpretation that will be discussed in detail. Highlights will be presented in both cases on how APT is changing the way we view the fundamental mechanisms dictating SCC of metals and glass alteration.