Capturing Radiation-induced Microstructure Evolution In Situ Through Direct Property Monitoring

Advanced materials development for nuclear systems is a time- and resource-intensive process relying on many iterations of material exposure and destructive testing to determine performance. Techniques such as in situ TEM can provide local structural information during irradiation, but no current methods are able to continuously monitor bulk thermal and mechanical properties. A method with this ability would be transformational in pinpointing the onset of emergent irradiation-induced microstructural evolution - such as the transition from incubation to steady-state void swelling - on a much shorter time scale that traditional methods. For this purpose, we have adapted a time-resolved, non-destructive and non-contact photoacoustic technique known as transient grating spectroscopy (TGS). This method is able to extract elastic and thermal transport properties from a surface on the same length scale to which ion beams can impose damage. Following ex situ validation, we developed an in situ TGS beamline experiment for concurrent ion beam irradiation and property monitoring on the 6 MV tandem accelerator at the Ion Beam Laboratory at Sandia National Laboratories. This experiment is used to study radiation-induced evolution in metals and alloys at orders-of-magnitude finer resolution in applied dose than is possible with traditional methods. We are now able to provide the type of rapid, engineering-relevant data necessary to speed the innovation cycle in nuclear material development. Moving forward, these methods will be used as screening and down-selection tools to expedite the design and testing process for advanced nuclear materials.