Neutron and X-ray Scattering
When used together, neutrons and high-energy x-rays provide a supremely powerful scientific tool for mining details about the structure of materials.
- Donald Brown
Pushing the limits of materials discovery
By using the probing power of neutrons in tandem with that of high energy x-rays, Los Alamos researchers are exploring previously inaccessible time and spatial scales, revealing details that aid our quest to control materials with properties optimized for specific functions.
To obtain the best possible experimental results, we perform this research at facilities including
- Lujan Center at the Los Alamos Neutron Science Center, Los Alamos National Laboratory
- Cornell High Energy Synchrotron Source, Cornell University
- Advanced Photon Source and Dynamic Compression Sector, Argonne National Laboratory
- Linear Coherent Light Source, SLAC National Accelerator Laboratory
Micrograph from a study of the stability of the two-phase (α/ω) microstructure of shocked zirconium. A sample of sintered ceramic UO2 nuclear fuel material undergoes high temperature grain growth in the x-ray hutch. Los Alamos researchers and collaborators prepare an experiment using high-energy x-ray diffraction microscopy to monitor grain growth in ceramic nuclear fuels at operating temperatures.
Using the neutron scattering and synchrotron x-ray capabilities available at these facilities, Los Alamos researchers are realizing the benefit of probing materials at
- Submicron length scales
- Millisecond (or faster) time scales
- Volume fractions less than 0.1 percent
to enable in situ research to design, discover, and control materials.
This research is in anticipation of MaRIE, Los Alamos National Laboratory’s proposed Matter-Radiation Interactions in Extremes experimental facility, which will be used to discover and design the advanced materials needed to meet future national security and energy security challenges.
Our staff members serve on important review committees:
U.S. Department of Energy Office of Basic Energy Sciences scientific and technical peer review, Ames National Laboratory, Olivier Gourdon
SRC Committee, Oak Ridge National Laboratory neutron scattering proposal review, reflectivity subcommittee, Erik Watkins
High Flux Isotope Reactor Biosciences review, Rex Hjelm Jr.
National Institute of Standards and Technology, Center of Neutron Scattering Research review, Rex Hjelm Jr.
Stability of the two phase (α/ω) microstructure of shocked zirconium
- High pressure omega-phase of zirconium is retained following dynamic shock events to high pressure (>7GPa).
- In situ x-ray diffraction measurements during heating and deformation of the shocked zirconium monitor the phase evolution during reverse (omega to alpha) transformation.
- Reverse transformation is athermal in our observations; that is, it occurs with time while holding at constant temperature.
- Defects in the omega phase appear to control reverse transformation to an alpha particle. With heating, dislocation density in the omega phase decreases. At a critical level, reverse transformation proceeds.
Residual stress in monolithic Al-clad U10Mo nuclear fuel plates
- Monolithic U10Mo fuel plates are being developed to replace highly enriched uranium with low enriched uranium in U.S. research reactors yet to be converted.
- Thermal expansion mismatch between Al cladding and U10Mo fuel results in residual stresses.
- Using 90-kiloelectron volt x-ray diffraction, determined lattice parameters as a function of position and orientation and, subsequently, to calculate residual stress in the fuel.
- In-plane compressive stresses approaching 300 megapascals observed in the fuel.
In situ grain grown in ceramic (UO2) nuclear fuel
- Grain boundary structure of nuclear fuels for power reactors is critical because it provides a shortcut path for radioactive fission products (e.g., Xe and Kr) to travel from microstructure to the area surrounding the fuel (the plenum) and can result in rupture of fuel cladding.
- With high-energy x-ray diffraction microscopy, we monitor grain morphology evolution (size and shape) of ceramic fuel before and after thermal conditions representative of those perceived by fuel in a reactor (i.e., ~2000 degrees Celsius).
- Next step: in situ measurements while at temperature.
- National Nuclear Security Administration is the steward of the Los Alamos Neutron Science Center.
- For the 2014-2015 Lujan Center run cycle, Science Campaign 1 was the main sponsor based upon the relevance of the proposed measurements to the program’s need to develop and validate science-based models to better predict the performance of nuclear weapons.