Atom Probe Tomography of Structural Materials for Nuclear Reactors

As the world’s population continues to increase, carbon neutral energy resources like nuclear power become increasingly important. A major challenge facing the design of advanced nuclear power systems lies in finding appropriate materials that demonstrate the needed material properties as well as radiation and high temperature resistance. For current generations of light water reactors, the Fukushima plant disaster revealed a problem with using Zr-based fuel cladding because of the hydrogen generation during the core meltdown. New cladding materials such as ferritic-based alloys and SiC materials are now being investigated as possible replacements. To develop an understanding of material performance under neutron irradiation requires detailed knowledge of the evolution of the materials microstructure both before and after irradiation. The damage processes occur at the nanoscale and require characterization techniques that can probe down to the atomic level to capture the chemical changes induced by exposure to the operating environment of nuclear reactors.
Atom probe tomography (APT) provides three-dimensional analysis of materials on the scale of nm, and in some cases atomic plane resolution is achievable. Analysis of composition as well as spatial location of second phases, grain boundary segregation, and nanoclusters is possible using APT, contributing unique insight into microstructural changes under irradiation. The proposal requests the use of the Local Electrode Atom Probe (LEAP) 4000X HR to analyze irradiated F/M steel samples and silicon carbide as well as other relevant metal and ceramic specimens that have been irradiated and prepared by targeted focused ion beam milling. The proposed work will also include time on the Quanta 3D FIB located in the Rad EMSL complex to prepare samples from irradiated materials.