Assessment of He migration and trapping interactions with microstructural features in ferritic alloys

Full text of publication follows: One of the key challenges facing the development of high performance, long-lived fusion materials is managing the high level of helium generated in first wall and blanket structures. Understanding the kinetics and energetics of helium migration and its interactions with various micro- and nano-structural features is a key to ensuring resistance of these materials to radiation damage and helium embrittlement. While many experimental and computational efforts have been devoted to studying helium in iron and ferritic alloys, a comprehensive understanding of the energetics of helium interactions and bubble nucleation and growth does not yet exist. In this presentation, we review the current knowledge of helium transport mechanisms, and the interactions of helium with other radiation-induced defects and microstructural features, that are believed to control helium bubble nucleation and growth kinetics. This overview will also assess the consistency between experimental observations, predominately involving thermal helium desorption spectroscopy of ion-implanted specimens and neutron irradiations with a helium implanter, and multi-scale modeling predictions, which span from ab initio electronic structure calculations to kinetic Monte Carlo and rate theory formulations of helium bubble evolution. Finally, the presentation will discuss the future experimental and computational challenges to addressing the question of whether a dispersion of Y-Ti-O nano-clusters can trap helium and inhibit the formation of grain boundary bubbles. (authors)