XMAT is a proposed extreme materials beamline for the Advanced Photon Source Upgrade aimed at developing new and more capable radiation tolerant materials for nuclear environments. For the first time, XMAT enables the study in real time of in situ damage in the bulk in materials under high (>2500) dpa conditions, by applying APS hard x-ray analysis techniques to materials under energetic (MeV/nucleon) heavy ion irradiation. It also enables the understanding of all forms of fission fragment and neutron collision damage. 

The proposed XMAT beamline at the Advanced Photon Source (APS) provides a unique opportunity for dramatically accelerating the development of nuclear fuels and materials, including accident tolerant LWR fuels and claddings, advanced LWR structural materials for plant life extension, and high-performance fuels and materials for advanced reactor and fuel cycle concepts. XMAT thus supports key goals of several DOE-NE Reactor and Fuel Cycle programs.

By applying APS hard x-ray analysis techniques to materials samples under energetic (MeV/nucleon) heavy ion irradiation, XMAT enables in-situ examination of irradiation effects in a system where the major experimental variables (e.g., temperature, applied load, and irradiation levels) are well controlled. The penetrating ability and accelerated dose impartation of energetic ions and the high spatial and temporal resolution afforded by APS x-rays combine to allow unprecedented in situ observation of radiation damage in the bulk of material samples, well beyond the range of surface sinks. The ability of the APS x-rays to isolate individual grains within the solid will reveal in a single sample many of the characteristics of radiation damage, including the effects of added interstitials, swift ion effects, and the role of interstitial/vacancy trapping. With this information the differences between ion and neutron irradiation may become more understandable.

Screening and testing of advanced materials, particularly those which are resistance to damage from irradiation, can be dramatically accelerated because dose accumulation is orders of magnitude faster with ion irradiation than neutron irradiation. Moreover, XMAT will improve the understanding of radiation damage phenomena and their complex interplay, which is essential for the improvement and validation of computational models of materials behavior. Such improvements would greatly benefit the evaluation of candidate materials and the design of new materials having desired characteristics.

XMAT Goals

• Couple new materials synthesis, predictive modeling, and accelerated ion-beam testing to enable transformative breakthroughs in advanced nuclear fuels and materials, waste forms, and separation technologies.
• Remove uncertainties, to the extent possible, for understanding differences between ion and neutron radiation.
• Provide insights into the extended response of materials radiation damage for the first time by employing a large damage rate/surface erosion rate of high-energy, heavy ions. This allows total damage doses to exceed several hundred thousand DPAs.
• Provide physical parameters to accurately model nuclear fuels.
• Provide for the first time both in situ X-ray scattering and three-dimensional characterization of defect dynamics. This will provide validation for computer simulations which will be needed to predict defect evolution under extreme irradiation.
• Enable study of a wide range of nuclear materials, including actinides and claddings.
• Improve understanding of damage and irradiation effects such as point defects and clusters, voids and gas bubbles, and dislocations needed to enable improved material design.
• Enhance the Advanced Test Reactor (ATR) materials and facility by enabling further (higher dose) study of ATR’s current materials library, as well as screening materials that would otherwise require extended testing.