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Title: Microstructural evolution of a uranium-10 wt.% molybdenum alloy for nuclear reactor fuels

Abstract

Low-enriched uranium-10 wt.% molybdenum (LEU-10wt.%Mo) is of interest for the fabrication of monolithic fuels to replace highly-enriched uranium (HEU) dispersion fuels in high performance research and test reactors around the world. In this work, depleted uranium-10wt.%Mo (DU- 10wt.%Mo) is used to simulate the solidification and microstructural evolution of LEU- 10wt.%Mo. Electron backscatter diffraction (EBSD) and complementary electron probe microanalysis (EPMA) reveal significant microsegregation present in the metastable γ-phase after solidification. Homogenization is performed at 800 and 1000 °C for times ranging from 1 to 32 h to explore the time-temperature combinations that will reduce the extent of microsegregation, as regions of higher and lower Mo content may influence local mechanical properties and provide preferred regions for γ-phase decomposition. We show for the first time that EBSD can be used to qualitatively assess microstructural evolution in DU-10wt.%Mo after homogenization treatments. Complementary EPMA is used to quantitatively confirm this finding. Homogenization at 1000 °C for 2 to 4 h reduces the regions that contain 8 wt.% Mo or lower, whereas homogenization at 1000 °C for longer than 8 h effectively saturates Mo chemical homogeneity, but results in substantial grain growth. The appropriate homogenization time will depend upon additional microstructural considerations, such asmore » grain growth and intended subsequent processing. Higher carbon LEU-10wt.%Mo generally contains more inclusions within the grains and at grain boundaries after solidification. The effect of these inclusions on microstructural evolution (e.g. grain growth) during homogenization and as potential γ-phase decomposition nucleation sites is unclear, but likely requires additional study.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1492570
Alternate Identifier(s):
OSTI ID: 1246218
Report Number(s):
LA-UR-15-21417
Journal ID: ISSN 0022-3115
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 465; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Clarke, A. J., Clarke, K. D., McCabe, R. J., Necker, C. T., Papin, P. A., Field, R. D., Kelly, A. M., Tucker, T. J., Forsyth, R. T., Dickerson, P. O., Foley, J. C., Swenson, H., Aikin, R. M., and Dombrowski, D. E. Microstructural evolution of a uranium-10 wt.% molybdenum alloy for nuclear reactor fuels. United States: N. p., 2015. Web. doi:10.1016/j.jnucmat.2015.07.004.
Clarke, A. J., Clarke, K. D., McCabe, R. J., Necker, C. T., Papin, P. A., Field, R. D., Kelly, A. M., Tucker, T. J., Forsyth, R. T., Dickerson, P. O., Foley, J. C., Swenson, H., Aikin, R. M., & Dombrowski, D. E. Microstructural evolution of a uranium-10 wt.% molybdenum alloy for nuclear reactor fuels. United States. doi:10.1016/j.jnucmat.2015.07.004.
Clarke, A. J., Clarke, K. D., McCabe, R. J., Necker, C. T., Papin, P. A., Field, R. D., Kelly, A. M., Tucker, T. J., Forsyth, R. T., Dickerson, P. O., Foley, J. C., Swenson, H., Aikin, R. M., and Dombrowski, D. E. Tue . "Microstructural evolution of a uranium-10 wt.% molybdenum alloy for nuclear reactor fuels". United States. doi:10.1016/j.jnucmat.2015.07.004. https://www.osti.gov/servlets/purl/1492570.
@article{osti_1492570,
title = {Microstructural evolution of a uranium-10 wt.% molybdenum alloy for nuclear reactor fuels},
author = {Clarke, A. J. and Clarke, K. D. and McCabe, R. J. and Necker, C. T. and Papin, P. A. and Field, R. D. and Kelly, A. M. and Tucker, T. J. and Forsyth, R. T. and Dickerson, P. O. and Foley, J. C. and Swenson, H. and Aikin, R. M. and Dombrowski, D. E.},
abstractNote = {Low-enriched uranium-10 wt.% molybdenum (LEU-10wt.%Mo) is of interest for the fabrication of monolithic fuels to replace highly-enriched uranium (HEU) dispersion fuels in high performance research and test reactors around the world. In this work, depleted uranium-10wt.%Mo (DU- 10wt.%Mo) is used to simulate the solidification and microstructural evolution of LEU- 10wt.%Mo. Electron backscatter diffraction (EBSD) and complementary electron probe microanalysis (EPMA) reveal significant microsegregation present in the metastable γ-phase after solidification. Homogenization is performed at 800 and 1000 °C for times ranging from 1 to 32 h to explore the time-temperature combinations that will reduce the extent of microsegregation, as regions of higher and lower Mo content may influence local mechanical properties and provide preferred regions for γ-phase decomposition. We show for the first time that EBSD can be used to qualitatively assess microstructural evolution in DU-10wt.%Mo after homogenization treatments. Complementary EPMA is used to quantitatively confirm this finding. Homogenization at 1000 °C for 2 to 4 h reduces the regions that contain 8 wt.% Mo or lower, whereas homogenization at 1000 °C for longer than 8 h effectively saturates Mo chemical homogeneity, but results in substantial grain growth. The appropriate homogenization time will depend upon additional microstructural considerations, such as grain growth and intended subsequent processing. Higher carbon LEU-10wt.%Mo generally contains more inclusions within the grains and at grain boundaries after solidification. The effect of these inclusions on microstructural evolution (e.g. grain growth) during homogenization and as potential γ-phase decomposition nucleation sites is unclear, but likely requires additional study.},
doi = {10.1016/j.jnucmat.2015.07.004},
journal = {Journal of Nuclear Materials},
number = C,
volume = 465,
place = {United States},
year = {2015},
month = {7}
}

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