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Evaluating the microstructure and origin of nonmetallic inclusions in as-cast U-10 Mo fuel

Journal Article · · Journal of Nuclear Materials

Low enriched uranium alloyed with 10 wt% molybdenum (U-10Mo) has been identified as a promising alternative to highly enriched uranium oxide dispersion fuels for use in high performance research and test reactors. Manufacturing U-10Mo alloy fuel involves several complex thermomechanical processing steps and understanding the microstructure and its evolution throughout the various fabrication steps is critical to enable the deployment of a reliable fuel production capability. Nonmetallic inclusions are often found in U castings and may affect subsequent fuel processing steps and microstructure evolution. Yet the origin of these inclusions is not well established. To elucidate the origin and formation mechanisms, nonmetallic inclusions in U-10Mo castings were characterized on sub-nanometer to millimeter scales. Inclusion distribution, morphology, size, and composition were characterized. Inclusions were estimated to comprise ~ 0.4 % of the fuel (by area), were identified at both grain boundaries and grain interiors, and were found to have varying morphologies (e.g., core-shell, elongated, nanoscale). All inclusions were either uranium carbides or oxides, or a combination of the two (i.e., dual-phase inclusions). Analysis of inclusions via atom probe tomography (APT) revealed that carbides and oxides were hypostoichiometric, with minor amounts of additional impurity elements present (e.g., Si, H). All inclusions analyzed were found to be enriched to ~20 at. % 235U, indicating that the inclusions formed during the downblending of HEU metal with depleted uranium via the casting process.

Research Organization:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
1808549
Report Number(s):
PNNL-SA-158125
Journal Information:
Journal of Nuclear Materials, Vol. 554
Country of Publication:
United States
Language:
English

References (31)

Performance of Metallic Fuels and Blankets in Liquid-Metal Fast Breeder Reactors journal May 1984
A US perspective on fast reactor fuel fabrication technology and experience part I: metal fuels and assembly design journal June 2009
Metallic fuels for advanced reactors journal July 2009
Microstructural characteristics of DU–xMo alloys with x=7–12wt% journal June 2009
Oxidation of uranium alloys in carbon dioxide and air journal June 1961
Effect of homogenization and hot rolling on the mechanical properties, microstructure and corrosion behavior of U–10Mo monolithic fuel journal December 2019
Crystallographic and compositional analysis of impurity phase U2MoSi2C in UMo alloys journal June 2019
Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy journal June 2018
Correlating nanoscale secondary ion mass spectrometry and atom probe tomography analysis of uranium enrichment in metallic nuclear fuel journal January 2021
U-Mo Monolithic Fuel for Nuclear Research and Test Reactors journal November 2017
Modeling the homogenization kinetics of as-cast U-10wt% Mo alloys journal April 2016
Microstructural evolution of a uranium-10 wt.% molybdenum alloy for nuclear reactor fuels journal October 2015
Phase transformation of metastable discontinuous precipitation products to equilibrium phases in U10Mo alloys journal November 2018
Evolution of microstructure and texture during thermo-mechanical processing of a two phase Al0.5CoCrFeMnNi high entropy alloy journal August 2016
Current issues in recrystallization: a review journal November 1997
Drag Effects of Solute and Second Phase Distributions on the Grain Growth Kinetics of Pre-Extruded Mg-6Zn Alloy journal December 2016
A Potts Model parameter study of particle size, Monte Carlo temperature, and “Particle-Assisted Abnormal Grain Growth” journal December 2020
A Threshold Selection Method from Gray-Level Histograms journal January 1979
Three-dimensional nanoscale characterisation of materials by atom probe tomography journal November 2016
Quantitative atom probe analysis of carbides journal May 2011
The uranium-molybdenum equilibrium diagram below 900° C journal March 1960
Thermomechanical process optimization of U-10wt% Mo – Part 2: The effect of homogenization on the mechanical properties and microstructure journal October 2015
Controlling residual hydrogen gas in mass spectra during pulsed laser atom probe tomography journal February 2017
Use of Tribocor 532N for a carbon-free induction furnace for vacuum-induction melting and casting of uranium and its alloys journal November 1987
The oxidation of uranium in carbon dioxide and carbon monoxide (A review) journal October 1969
A review of uranium corrosion by hydrogen and the formation of uranium hydride journal May 2018
The oxidative corrosion of carbide inclusions at the surface of uranium metal during exposure to water vapour journal November 2011
Asymptotics of Coupled Reaction-Diffusion Fronts With Multiple Static and Diffusing Reactants: Uranium Oxidation in Water Vapor journal January 2020
Corrosion of uranium in liquid water under contained conditions with a headspace deuterium overpressure. Part 2: The ternary U + H2O(l) + D2 system journal May 2019
Atomic-scale Studies of Uranium Oxidation and Corrosion by Water Vapour journal July 2016
Corrosion of uranium in liquid water under vacuum contained conditions. Part 1: The initial binary U + H2O(l) system journal May 2019