Abstract
The realization of fusion energy is a formidable challenge, with significant achievements resulting from close integration of the plasma physics and applied technology disciplines. Presently, the most significant technological challenge for planned fusion power systems is the inability of current materials and components to withstand the harsh fusion nuclear environment. The overarching goal of the ORNL Fusion Materials Program is to provide the applied materials science support and materials understanding to underpin the ongoing DOE Office of Science Fusion Energy Program while developing materials for fusion power systems. In doing so the program continues to be integrated both with the larger U.S. and international fusion materials communities and with the international fusion design and technology communities.
This long-running ORNL program continues to pursue development of low activation structural materials such as the reduced activation ferritic/martensitic steels, higher strength/higher creep resistant/radiation resistant advanced steels, and silicon carbide composites. Focus tasks within the steels portfolio are development of castable nanostructured alloys, exploratory work on Bainitic steels and a helium-effects experiment using isotopically separated iron-54. Parallel to this is the increased emphasis on radiation effects, high heat flux testing and the development of refractory metals. This includes the use of an ORNL Plasma Arc Lamp Facility adapted for the thermal testing of irradiated materials, the development and evaluation of new tungsten materials, and the study and understanding of the irradiation performance of tungsten. In each case the materials are being developed in a design-informed fashion where properties improvements are led by fusion-relevant design studies and directed at advancing the Technology Readiness Level of the material systems.
New work supported by an Early Career Award is looking in depth at the materials side of the plasma materials interactions, characterizing the materials response to plasma impingement and determining the controlling mechanisms of the materials behavior.
A limited effort continues to examine functional and exploratory materials. In the area of diagnostics, ORNL supports basic irradiation materials science of ceramics that could be used in diagnostic systems. For high-temperature superconductors, ORNL has completed a limited program to quantify the irradiation sensitivity of the most recently developed tape materials. Studies of the MAX-phase ceramics, high entropy alloys, and bulk metallic glasses were continued as the materials that potentially possess exceptional or unique radiation tolerance.
Finally, this program integrates fundamental modeling into the development efforts as much as practicable.
This fusion materials program makes heavy reliance on neutron irradiation in HFIR, the High Flux Isotope Reactor at ORNL. This is complemented by use of the ORNL-University of Tennessee ion irradiation facility and other available accelerator facilities when these are better suited to explore fundamental aspects of materials behavior under irradiation.
This document summarizes FY2016 activities supporting the Office of Science, Office of Fusion Energy Sciences Materials Research for MFE carried out by ORNL. The organization of the report is mainly by material type, with sections on specific technical activities.
A continuing activity initiated several years ago, “Materials Engineering in Support of the FNSF Program,” is reported in Section 10.
The fusion materials effort consists of a wide array of tasks and collaborations both within the US and with international partners. The major continuing international collaborating partners are the Japan Agency for Quantum and Radiological Science and Technology (QST, reorganized and transferred from Japan Atomic Energy Agency, the US DOE-JAEA collaboration, focused on structural materials), the Japanese National Institute for Fusion Sciences (the PHENIX collaboration, emphasizing plasma facing materials and tritium fuel issues) and the Karlsruhe Institute of Technology in Germany (examining steel materials). Separately identified since FY2015 is a domestic collaboration, designed to provide specimens from the archive of HFIR-irradiated material to other OFES funded researchers to further their studies. Status of this work is reported in Section 12.1.