Thermal Property Characterization, Modeling, and Theory in Extreme Environments: Nuclear Fuel Performance & Advanced Thermal Analysis
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Janelle Wharry, Purdue University; Mukesh Bachhav, Idaho National Laboratory; Marat Khafizov, Ohio State University; Eric Lass, University of Tennessee-Knoxville; Vikas Tomar, Purdue University; Tiankai Yao, Idaho National Laboratory; Cody Dennett, Commonwealth Fusion Systems; Karim Ahmed, Texas A&M University
Thursday 8:30 AM
March 18, 2021
Room: RM 53
Location: TMS2021 Virtual
Session Chair: Janelle Wharry, Purdue University; Elizabeth Sooby Wood, University of Texas at San Antonio
8:30 AM
Ultra-high Lattice Thermal Conductivity and the
Effect of Pressure in Superhard Hexagonal BC2N: Safoura Nayeb Sadeghi1; S. Mehdi Vaez Allaei2; Mona Zebarjadi1; Keivan Esfarjani1; 1University of Virginia; 2University of Tehran
Hexagonal BC2N is a superhard material recently identified to be comparable to or even harder than cubic boron nitride (c-BN). Using a first-principles approach to calculate force constants and an exact numerical solution to the phonon Boltzmann equation, we show that BC2N has a high lattice thermal conductivity exceeding that of c-BN owing to the strong C–C and B–N bonds, which produce high group velocities. Its coefficient of thermal expansion (CTE) is found to match that of Si above 400 K The combination of large thermal conductivity and a good CTE match with that of Si, makes BC2N a promising material for use in thermal management and high-power electronics applications. We show that the application of compressive strain increases the thermal conductivity significantly. This enhancement results from the overall increased frequency scale with pressure, which makes acoustic and optic velocities higher, and weaker phonon–phonon scattering rates.
8:50 AM Invited
Performance of UO2 Reactor Fuel with High Thermal Conductivity Additives: Michael Tonks1; Floyd Hilty1; 1University of Florida
The thermal conductivity of UO2 is the lowest of all uranium-based nuclear reactor fuels, hurting the efficiency with which heat can be conducted through the fuel and converted to electricity. In order to increase the thermal conductivity of the fuel, composite fuels have been created in which materials with a much higher thermal conductivity are added to UO2. In this work, we summarize the proposed composite fuels and identify approaches to tailor the additive microstructure to maximize its impact on the thermal conductivity. We then discuss other ways in which the additives may alter the fuel performance and use finite element simulations to determine the impact of fission gas segregation to the additive interfaces on the composite fuel thermal conductivity.
9:20 AM Invited
Atmosphere Controlled Thermogravimetric Analysis as a Tool to Screen, Test and Qualify Advanced Fuels under Extreme Conditions: Elizabeth Sooby1; 1University of Texas at San Antonio
The quantification and classification of the response of advanced nuclear fuel forms to reactor off-normal and accident conditions resulting in oxidant exposure has been at the forefront of fuels testing for the last decade. Though static testing provides insight to material degradation and kinetics, dynamic measurement of the response of a fuel form to oxidant exposure is a superior method of testing and qualification, if performed under relevant and controlled atmospheres. Presented will be the utilization of thermogravimetric analysis in precision engineered atmospheres to probe the susceptibility of advanced and novel fuel forms to off-normal conditions. Included will be screening studies for dopants and additives to accident tolerant fuels, specifically U3Si2 and UN compared to UO2 and uranium metal. Additionally, the latest in oxidation testing in advanced gas reactor relevant atmospheres of TRISO particle fuel and graphite matrix material will be covered.
9:50 AM
Thermal Stability of Metallic Multilayers with TripleJjunctions: Tongjun Niu1; Yifan Zhang1; Jaehun Cho1; Jin Li1; Haiyan Wang1; Xinghang Zhang1; 1Purdue University
Nanostructured metallic multilayers have attracted significant attention due to their high mechanical strength and superb radiation resistance. Here we compare the thermal stability of CuX/Fe multilayer with triphase triple junctions comparing to Cu/Fe multilayer. Annealing at elevated temperatures leads to the complete breakdown of layer structure and spheroidization of the Cu/Fe multilayer. In contrast, the structure of CuX/Fe multilayer remains stable after annealing with minor perturbations along layer interface. The mechanisms that lead to the enhanced thermal stability of CuX/Fe multilayer will be discussed. This study provides some insight on the design of stable metallic nanocomposites.
10:10 AM
Energy Balance Investigation of Close-coupled Optimized-pressure Gas Atomization Pour-tube Design Geometry to Prevent Melt Freeze-off: Franz Hernandez1; Eric Deaton1; Iver Anderson1; 1Ames Laboratory of US DOE
Metal additive manufacturing (AM) is an evolving technology, and the supply of quality feedstock material needs to follow suit. Closed-coupled optimized-pressure gas atomization (CCOPGA) promises narrow size distribution, spherical powder, and optimized use of gas. However, pour-tube melt solidification is an obstacle to enabling a wider alloy palate. Many solutions involve adding melt superheat, but do not account for all cooling influences. While the Joule-Thomson effect and forced convection promotes high cooling rates for the powder, excessive heat loss can lead to freeze-off. Therefore, optimizing the melt delivery geometry is needed to reduce freeze-off and down time. Analytical and numerical models are employed to study the heat transfer process between the pour tube and the surroundings for CCOPGA of both Ni and Ca melts. The effects of normalized length, radius, and thermal diffusivity are considered. Work supported by USDOE-EERE-AMO and USDOE-OE through Ames Laboratory Contract No. DE-AC02-07CH11358.