Testing Materials For Fusion Power Plants

Materials for future fusion power plants are to be developed at the Garching research campus. As part of a new program of the Federal Ministry of Research, Technology and Space (BMFTR), several research groups from the Heinz Maier-Leibnitz Research Neutron Source (FRM II) at the Technical University of Munich (TUM) and the Max Planck Institute for Plasma Physics (IPP) are pooling their expertise.

Inside a fusion reactor, materials are simultaneously exposed to extreme temperatures, mechanical stress, and intense particle radiation. This alters the crystal lattice, creates defects and pores, and can cause material failure. Affected materials include ferritic steels such as EUROFER97, tungsten and tungsten alloys for the reactor inner wall, as well as copper alloys for cooling components. Under neutron bombardment, rhenium also forms in tungsten - a change that affects the material properties.

This is where FUMA comes in, the "Competence Center for the Optimization of Fusion Materials." It brings together one positron research group and three neutron research groups from FRM II, as well as two IPP groups whose methods complement one another. One group is investigating additively manufactured components and welded joints, while another is analyzing pores and internal stresses under industry-relevant conditions.

"With our positron spectroscopy at FRM II, we want to understand material damage at the atomic level," explains project coordinator Prof. Christoph Hugenschmidt of TUM. "Using the antiparticles of electrons, we can trace how the smallest defects develop into larger structures that ultimately determine the service life of a material." Prof. Christian Pfleiderer, Scientific Director at FRM II, adds: "The neutron methods used at FRM II provide unique insights into the structure of fusion materials, from the atomic scale to the millimeter scale."

Hugenschmidt explains why Garching offers ideal conditions for the project: "Here on site, IPP contributes outstanding expertise on materials and components for a future fusion reactor." In addition, the site offers unique experimental capabilities: heat loads of up to 20 megawatts per square meter, as well as targeted material damage caused by neutron irradiation, can be studied under realistic conditions.

The long-term goal is to be able to reliably predict the service life of materials in a fusion reactor. The groups are jointly developing a measurement program: IPP defines the research priorities for materials-related questions and prepares samples, while the analysis groups at FRM II continue to improve their neutron- and positron-based instruments and investigate the damage mechanisms.