Characterization of the lithium concentration and distribution as a function of depth for alumina coatings after exposure to PbLi

Abstract

The development of multifunctional barriers that prevent tritium leaks from the breeding blanket and corrosion of the structural steel is essential for safe, viable and cost-effective fusion reactor operation. Al2O3 coatings are considered to be one of the most promising options to act as tritium permeation barrier (TPB). However, previous studies have shown that lithium from the breeding blanket penetrates into these coatings and reacts with them forming lithium aluminate phases. The diffusion of lithium into the coating may influence its performance, particularly under neutron irradiation. In this study, we characterize the Li content and distribution as a function of depth for Al2O3 coatings deposited by pulsed laser deposition on EUROFER substrate after exposure to PbLi, at a constant temperature of 550 ◦C, for times of up to 7000 h, under stagnant conditions. We do it by using secondary ions mass spectroscopy and, a combination of ion beam analysis techniques (nuclear reaction analysis and Rutherford backscattering spectroscopy). Finally, we discuss the possible consequences of lithium diffusion in the coating performance under neutron irradiation in relation to the behavior of light species, produced out of transmutation reactions, and to the possible radiation induced change in the coating morphology.