Materials in Nuclear Energy Systems (MiNES) 2021: Fuels and Actinide Materials- Thermal Properties, UN and UC Fuels II
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory
Thursday 8:00 AM
November 11, 2021
Room: Monongahela
Location: Omni William Penn Hotel
Session Chair: Najeb Abdul-Jabbar, Los Alamos National Laboratory
8:00 AM Invited
Thermal Analysis of Advanced Nuclear Fuels during Simulated Off-normal Events: Elizabeth Sooby1; Brian Brigham1; Katherine Montoya1; Geronimo Robles1; 1University of Texas at San Antonio
The evolution of commercial reactor fuel forms and development of the next generations of reactors spark a demand to close existing data gaps in the performance of advanced reactor fuel concepts. Commercial fuel vendors are targeting higher uranium density fuels to enhance fuel economy and better accommodate accident tolerant cladding, and the leading designs for small modular reactors are looking toward particle fuel architectures. A number of data gaps and/or inconsistencies exist for these lesser known fuel concepts, including their performance during off-normal events involving oxidant ingress. Presented is the utilization of thermal analysis in precision engineered atmospheres to probe the stability of high uranium density and particle fuel forms during high temperature transients. In each of the studies presented, a combination of thermogravimetric, differential thermal, and evolved gas analysis are employed in a dynamic measurement of the response of advanced nuclear materials to accident conditions and atmospheres.
8:40 AM
Development and Application of a UN Potential to Defect Properties and High Temperature Elastic Constants: Vancho Kocevski1; Michael Cooper1; Antoine Claisse2; David Andersson1; 1Los Alamos National Laboratory; 2Westinghouse Electric Sweden
Atomic-scale modeling of thermophysical and defect properties of UN play an important role in establishing improved models, thus having an accurate interatomic potential is crucial for generating reliable data at finite temperatures using molecular dynamic simulations. We report a new interatomic potential for UN, based on a combination of many-body and pairwise interactions, fitted to experimental and density functional theory (DFT) data. We successfully reproduced experimental lattice parameters, thermal expansion, single crystal elastic constants, and temperature dependent heat capacity. The potential also performs reasonably well in reproducing the DFT calculated energy of stoichiometric defect reactions, and defect migration barriers. Furthermore, the potential predicted that a U split interstitial is more stable than a regular interstitial, later confirmed by DFT calculations. The potential was also used to predict UN single crystal elastic constants and elastic properties at different temperatures, showing that UN becomes softer and more compressible with increasing temperature.
9:00 AM
Chemical Interaction and Incorporation of Lead with Uranium Nitride Fuels: Andre Broussard1; Kun Yang1; Jie Lian1; 1Rensselaer Polytechnic Institute
Uranium Nitride (UN) has been identified as a prime fuel candidate for Lead Cooled Fast Reactors and as part of a fuel-cladding-coolant combination consisting of Uranium Nitride, Alumina-forming Austenitic Alloys, and Lead (Pb). Here we report the findings of using spark plasma sintering (SPS) to synthesis Pb-doped UN pellets with different amounts (5 and 10 wt%) and different sintering parameters (temperature and pressure). Characterization of pellets is performed via Scanning Electron Microscopy, Energy Dispersive Spectroscopy and X-ray Diffraction. Results of characterization for Pb-doped UN pellet sintered at 1550°C exhibit evaporation of Pb out of the UN pellet while a pellet sintered at 1450°C displays diffusion of Pb into the UN matrix. Ongoing experimentation is being conducted at lower temperatures to verify this result. Further experimentation is planned to incorporate UN pellets into liquid Pb to simulate a reactor environment and determine if U dissolves in liquid Pb.
9:20 AM
Phase and Thermodynamic Analysis of Uranium Mononitride in High-temperature Steam Light Water Reactor Atmospheres: Geronimo Robles1; Brian Brigham1; Joshua White2; Elizabeth Sooby1; 1University of Texas at San Antonio; 2Los Alamos National Laboratory
Uranium mononitride (UN) is investigated here as an accident tolerant fuel candidate for deployment in light water reactors (LWR) due to advantages in uranium density and thermal conductivity when compared to UO2. Implementation of a fuel with these properties would allow for increased fuel economy, lower fuel centerline temperatures and longer response times during off-normal conditions. However, data for UN exposures to off-normal LWR atmospheres is limited. Presented here are the results from experimental measurements of UN pellets sintered to theoretical densities > 90% and oxidized in high temperature steam and steam+H2. Experiments were performed under thermal ramp conditions to 1200 °C and isothermal holds at 400 and 500 °C. Thermogravimetric analysis confirmed a dependence on pellet density to the oxidation dynamics under both ramp and isotherms. Characterization techniques include powder x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy detailing the oxidation products and degradation mechanisms present following exposure.
9:40 AM Break