Dr. Jamie Marian
Seminar Information
As the fusion community fast moves towards the conceptualization and construction of fusion reactor prototypes, the materials engineering community must carefully weigh the strengths and weaknesses of the available materials irradiation facilities to maximize the usefulness of testing and identify the parameter space susceptible of being explored in each case. In this context, theory, modeling and simulation can act as a bridge to understand the differences in material behavior between irradiations in a nominal 14-MeV neutron environment and non-fusion irradiation facilities. The last decades have experienced substantial progress in terms of the accuracy, scale, and relevance of materials modeling under fusion reactor operation. Increasingly more complex and realistic material microstructures can now be simulated under fusion-representative conditions, complementing experiments and solidifying our understanding of materials behavior under meaningful dose rates, temperatures, gas atom-to-dpa ratios, and spectral details. As well, while many challenges still remain, the experience acquired by modeling teams over the last few decades has now resulted in a set of ‘best-practices’ supported by a relatively wide community consensus with applications in a wide range of different operational scenarios. Current models can effectively capture irradiation damage buildup coupled to microstructural evolution, dose-rate and temperature dependent regimes, nuclear transmutation and gas atom evolution, solute mobilization by radiation enhanced diffusion, as well as the change in derivative quantities such as hardening, swelling, or creep. While important gaps in our understanding remain, particularly in terms of high dose and high temperature materials behavior, synergistic He/H effects in ferritic materials, pulsed irradiation, or chemical effects, modeling is presently in a good position to issue qualified materials behavior estimations in the anticipated operational range gap between a fusion reactor and an experimental facility. In particular, we will discuss potential differences in He- and H-to-dpa ratios, irradiation flux and pulsed regimes, probe volumes, and irradiation temperatures, as well as the potential implications of modeling long term transmutation-induced chemical composition changes, swelling, and creep. Finally, we will discuss the potential of new and improved techniques, including data-driven approaches, aided by an increased availability of computational resources, to push the envelope of our current understanding limits and improve error and uncertainty estimation of model predictions.
Prof Jaime Marian has a joint appointment in the Materials Science and Engineering and Mechanical and Aerospace Engineering Depts. at UCLA since 2014. Prior to that, he was a staff scientist at Lawrence Livermore National Laboratory, where he worked on the development of physics models for materials under extreme conditions. He holds a nuclear engineering degree from the Polytechnic University of Madrid, and a PhD in materials science. He did postdoctoral work at Caltech and was the recipient of a DOE Early Career Award.