The progress of any technology depends on the performance of the materials it employs. Materials used in nuclear technology suffer from degradation due to radiation. The goal of the research on nuclear materials is to understand the effects of radiation and use the knowledge gained to improve materials resistance for applications in energy production or storage of radioactive materials.
The changes that occur in materials by radiation can also be exploited to develop materials with special properties that cannot be achieved by conventional methods of synthesis. This has opened up new areas of research involving the use of radiation effects and radiation-based techniques for materials synthesis and characterization. Read on to learn about specific projects.
Irradiation-Assisted Stress Corrosion Cracking of Austenitic Stainless Steels
This program is investigating the influence of irradiation on the stress corrosion cracking process in stainless steels used in nuclear reactor cores. High energy protons are used in place of neutrons to induce grain boundary segregation and microstructural changes, eliminating the problem of sample activation and reducing sample analysis time from years to months. This work is led by Gary Was.
Materials for the Very High Temperature Gas Reactor
This experimental program addresses two of the materials challenges of the very high temperature gas reactor (VHTR). They are the oxidation of metallic components at temperatures up to 1000°C and the irradiation-induced creep that will occur in the TRISO fuel particles. Understanding these phenomena is critical to the development of materials that can operate in very high temperature environments. This work is led by Gary Was.
Behavior of Irradiated Materials in Supercritical Water
This program is focused on the behavior of materials in supercritical water, relevant to the supercritical water reactor. However, little is known about the behavior of materials in both the unirradiated and irradiated conditions. Materials irradiated with accelerator-produced ions and in reactor cores are studied and facilities to test neutron-irradiated materials have been built for that purpose. This work is led by Gary Was.
Radiation Induced Amorphization in Ceramics and Minerals
This program addresses fundamental issues in particle-solid interactions for structurally and compositionally complex ceramics. The effects of structural topology, bond-type, dose rate and irradiation temperature on the final state of the irradiated material are investigated. This work is led by Lumin Wang.
Radiation processing of novel patterned nanostructures
Energetic electron and ion beams are utilized to process 2-D and 3-D nanostructures in the surface region of metals, semiconductors and ceramics. These nanostructures include 3-D nano-scale void lattice and nanofibers arranged in micro-scale patterns that may have unique optical properties for potential applications in advanced micro- and nano-devices. The fundamental mechanisms for the formation of these nanostructures involve radiation stimulated self-organization processes. Both experiments and theoretical modeling/simulation are undertaken to fully understand these processes. This work is led by Lumin Wang.
Deformation and structural transformations in metallic glasses
Metallic glasses are metal alloys that do not exhibit crystalline order. They have high strength and can store large amounts of elastic energy. However, their plastic deformation is localized to nanometer-sized shear bands, making them macroscopically brittle. A challenge to practical applications of metallic glasses is to prevent their catastrophic failure along shear bands. The goal of current research is to gain an improved understanding of the structure, mechanical behavior and modification of shear bands, using a combination of experimental techniques and modeling. This work is led by Michael Atzmon.
Development of high performance ODS alloys
The research employs coordinated experiments to study swelling, radiation hardening and changes in mechanical properties not only of these ODS alloys, but also further-optimized ODS candidates resulting from these first-round studies. The project will identify key factors influencing radiation tolerance of new ODS alloys for further property optimization. To gain atomic scale understanding, the research integrates these experiments with modeling capabilities, including molecular dynamics and dislocation dynamics simulations to understand the roles of yttria and other dispersoids as well as their various dispersion modes on both microstructural changes and mechanical property changes.
Atomistic- and Meso-Scale Computational Simulations for Developing Multi-Timescale Theory for Radiation Degradation in Electronic and Optoelectronic Devices
The research is to simulate atomistic- and meso-scale behavior of defect evolutions in compound semiconductors, including ultrafast displacement cascade, intermediate defect stabilization and cluster formation, as well as slow defect reaction and migration. The fundamental mechanisms and knowledge gained from atomic- and meso-scale simulations will be input into rate-diffusion theory as initial conditions to calculate the steady-state distribution of point defects in a mesoscopic layered-structured system, thus allowing the development of a multi-timescale theory to study radiation degradation in electronic and optoelectronic devices. The long‑term goal is developing a fundamental understanding of defects and defect processes in compound semiconductors, including defect/property relationships, the effects of defects on transport processes, the aggregation of defects to form complex nanostructures, and the development of predictive models of behavior.
Computational Capability for Studying Pulse Shape Discrimination of Scintillator Materials
The research collaborates with the researchers at Pacific Northwest National Laboratory to identify and understand the elementary processes that give rise to the measurable performance characteristics of scintillator materials. Through the development of a firm theoretical understanding of scintillator physics, the research will provide a pathway to optimize current scintillators and lead to the science-driven candidate search for new scintillator materials. The application of these capabilities to predict the pulse shape discrimination capability of scintillator materials will be explored.