In search of θ-(Pu,Zr) in binary Pu–Zr: Thermal and microstructural analyses of Pu − 30Zr alloy

Assel Aitkaliyeva; Cynthia A. Adkins; Casey McKinney; Jacob Hirschhorn; Michael R. Tonks

doi:10.1016/j.jnucmat.2019.151875

In search of θ-(Pu,Zr) in binary Pu–Zr: Thermal and microstructural analyses of Pu − 30Zr alloy

Assel Aitkaliyeva, Cynthia A. Adkins, Casey McKinney, Jacob Hirschhorn, Michael R. Tonks

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

The existing Pu–Zr binary phase diagrams report the stability of the compound θ-(Pu,Zr) in the low temperature region between 300 and 0 °C. Furthermore, the current understanding is that θ-(Pu–Zr) is thermodynamically favored over the metastable δ-(Pu,Zr) phase. In an effort to shed light on the phases formed in Pu–Zr binary alloys and reduce uncertainties in the poorly defined boundary between the θ-(Pu,Zr), (θ+δ), δ-(Pu,Zr), and (θ+α-Zr) regions, Pu − 30Zr (in wt.%, equivalent 53 at.%) alloys were subjected to microstructural characterization, annealing, and differential scanning calorimetry (DSC). The results indicate that the alloy is composed of δ-(Pu,Zr) matrix, with a number of smaller, randomly distributed α-Zr precipitates. The phase transition temperatures (determined based on the DSC data) and phases identified in Pu − 30Zr alloys (based on crystallographic data) compare well to those predicted by the phase diagrams with the exception of the θ-(Pu–Zr) phase. Our data indicates that θ-(Pu–Zr) is metastable and can be observed only within a small temperature window (100–300 °C). The consecutive heating cycles remove θ-(Pu–Zr) from the system, and no traces of θ-(Pu–Zr) remain at room temperature, as evidenced by microstructural characterization. This calls for reevaluation of the binary Pu–Zr phase diagram, with particular attention paid to the existence of θ-(Pu–Zr) and its stability.

Original language	English
Article number	151875
Journal	Journal of Nuclear Materials
Volume	528
DOIs	https://doi.org/10.1016/j.jnucmat.2019.151875
State	Published - Jan 2020
Externally published	Yes

Funding

This work was supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-05ID14517, as part of Fuel Cycle Research and Development (FCRD) program of the US DOE and INL Laboratory Directed Research and Development (LDRD) program. Authors would like to acknowledge the staff of Fuel Manufacturing Facility (FMF), Electron Microscopy Laboratory (EML), and Analytical Laboratory at the Materials and Fuels Complex (MFC) at Idaho National Laboratory and Materials Characterization Suite (MaCS) at the Center of Advanced Energy Studies (CAES) for their effort in fabrication, handling, and transfer of the alloys used in this work. This work was supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-05ID14517 , as part of Fuel Cycle Research and Development (FCRD) program of the US DOE and INL Laboratory Directed Research and Development (LDRD) program. Authors would like to acknowledge the staff of Fuel Manufacturing Facility (FMF), Electron Microscopy Laboratory (EML), and Analytical Laboratory at the Materials and Fuels Complex (MFC) at Idaho National Laboratory and Materials Characterization Suite (MaCS) at the Center of Advanced Energy Studies (CAES) for their effort in fabrication, handling, and transfer of the alloys used in this work. Appendix A

Funders	Funder number
Center of Advanced Energy Studies
DOE Idaho Operations Office	DE-AC07-05ID14517
Fuel Cycle Research and Development
Idaho National Laboratory and Materials Characterization Suite
U.S. Department of Energy
Office of Nuclear Energy
Laboratory Directed Research and Development

Keywords

Metallic fuel
Microstructure
Phase identification
Phase transition temperatures
Plutonium-zirconium

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10.1016/j.jnucmat.2019.151875

Cite this

@article{3b245b6ebfcc47c8992097f348425e3b,

title = "In search of θ-(Pu,Zr) in binary Pu–Zr: Thermal and microstructural analyses of Pu − 30Zr alloy",

abstract = "The existing Pu–Zr binary phase diagrams report the stability of the compound θ-(Pu,Zr) in the low temperature region between 300 and 0 °C. Furthermore, the current understanding is that θ-(Pu–Zr) is thermodynamically favored over the metastable δ-(Pu,Zr) phase. In an effort to shed light on the phases formed in Pu–Zr binary alloys and reduce uncertainties in the poorly defined boundary between the θ-(Pu,Zr), (θ+δ), δ-(Pu,Zr), and (θ+α-Zr) regions, Pu − 30Zr (in wt.%, equivalent 53 at.%) alloys were subjected to microstructural characterization, annealing, and differential scanning calorimetry (DSC). The results indicate that the alloy is composed of δ-(Pu,Zr) matrix, with a number of smaller, randomly distributed α-Zr precipitates. The phase transition temperatures (determined based on the DSC data) and phases identified in Pu − 30Zr alloys (based on crystallographic data) compare well to those predicted by the phase diagrams with the exception of the θ-(Pu–Zr) phase. Our data indicates that θ-(Pu–Zr) is metastable and can be observed only within a small temperature window (100–300 °C). The consecutive heating cycles remove θ-(Pu–Zr) from the system, and no traces of θ-(Pu–Zr) remain at room temperature, as evidenced by microstructural characterization. This calls for reevaluation of the binary Pu–Zr phase diagram, with particular attention paid to the existence of θ-(Pu–Zr) and its stability.",

keywords = "Metallic fuel, Microstructure, Phase identification, Phase transition temperatures, Plutonium-zirconium",

author = "Assel Aitkaliyeva and Adkins, {Cynthia A.} and Casey McKinney and Jacob Hirschhorn and Tonks, {Michael R.}",

note = "Publisher Copyright: {\textcopyright} 2019 Elsevier B.V.",

year = "2020",

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doi = "10.1016/j.jnucmat.2019.151875",

language = "English",

volume = "528",

journal = "Journal of Nuclear Materials",

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T2 - Thermal and microstructural analyses of Pu − 30Zr alloy

AU - Aitkaliyeva, Assel

AU - Adkins, Cynthia A.

AU - McKinney, Casey

AU - Hirschhorn, Jacob

AU - Tonks, Michael R.

PY - 2020/1

Y1 - 2020/1

N2 - The existing Pu–Zr binary phase diagrams report the stability of the compound θ-(Pu,Zr) in the low temperature region between 300 and 0 °C. Furthermore, the current understanding is that θ-(Pu–Zr) is thermodynamically favored over the metastable δ-(Pu,Zr) phase. In an effort to shed light on the phases formed in Pu–Zr binary alloys and reduce uncertainties in the poorly defined boundary between the θ-(Pu,Zr), (θ+δ), δ-(Pu,Zr), and (θ+α-Zr) regions, Pu − 30Zr (in wt.%, equivalent 53 at.%) alloys were subjected to microstructural characterization, annealing, and differential scanning calorimetry (DSC). The results indicate that the alloy is composed of δ-(Pu,Zr) matrix, with a number of smaller, randomly distributed α-Zr precipitates. The phase transition temperatures (determined based on the DSC data) and phases identified in Pu − 30Zr alloys (based on crystallographic data) compare well to those predicted by the phase diagrams with the exception of the θ-(Pu–Zr) phase. Our data indicates that θ-(Pu–Zr) is metastable and can be observed only within a small temperature window (100–300 °C). The consecutive heating cycles remove θ-(Pu–Zr) from the system, and no traces of θ-(Pu–Zr) remain at room temperature, as evidenced by microstructural characterization. This calls for reevaluation of the binary Pu–Zr phase diagram, with particular attention paid to the existence of θ-(Pu–Zr) and its stability.

AB - The existing Pu–Zr binary phase diagrams report the stability of the compound θ-(Pu,Zr) in the low temperature region between 300 and 0 °C. Furthermore, the current understanding is that θ-(Pu–Zr) is thermodynamically favored over the metastable δ-(Pu,Zr) phase. In an effort to shed light on the phases formed in Pu–Zr binary alloys and reduce uncertainties in the poorly defined boundary between the θ-(Pu,Zr), (θ+δ), δ-(Pu,Zr), and (θ+α-Zr) regions, Pu − 30Zr (in wt.%, equivalent 53 at.%) alloys were subjected to microstructural characterization, annealing, and differential scanning calorimetry (DSC). The results indicate that the alloy is composed of δ-(Pu,Zr) matrix, with a number of smaller, randomly distributed α-Zr precipitates. The phase transition temperatures (determined based on the DSC data) and phases identified in Pu − 30Zr alloys (based on crystallographic data) compare well to those predicted by the phase diagrams with the exception of the θ-(Pu–Zr) phase. Our data indicates that θ-(Pu–Zr) is metastable and can be observed only within a small temperature window (100–300 °C). The consecutive heating cycles remove θ-(Pu–Zr) from the system, and no traces of θ-(Pu–Zr) remain at room temperature, as evidenced by microstructural characterization. This calls for reevaluation of the binary Pu–Zr phase diagram, with particular attention paid to the existence of θ-(Pu–Zr) and its stability.

KW - Metallic fuel

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KW - Phase identification

KW - Phase transition temperatures

KW - Plutonium-zirconium

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In search of θ-(Pu,Zr) in binary Pu–Zr: Thermal and microstructural analyses of Pu − 30Zr alloy

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In search of θ-(Pu,Zr) in binary Pu–Zr: Thermal and microstructural analyses of Pu − 30Zr alloy

Abstract

Funding

Keywords

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Cite this

In search of θ-(Pu,Zr) in binary Pu–Zr: Thermal and microstructural analyses of Pu − 30Zr alloy