Microstructural characterization of the as-cast and annealed Pu-10Zr alloy

Assel Aitkaliyeva; Cynthia A. Adkins; Jacob Hirschhorn; Casey McKinney; Michael R. Tonks; Fidelma Giulia Di Lemma

doi:10.1016/j.jnucmat.2019.05.051

Microstructural characterization of the as-cast and annealed Pu-10Zr alloy

Assel Aitkaliyeva, Cynthia A. Adkins, Jacob Hirschhorn, Casey McKinney, Michael R. Tonks, Fidelma Giulia Di Lemma

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

5 Scopus citations

Abstract

Phase diagrams constructed for the Pu-Zr binary system report the existence of θ-(Pu,Zr), δ-(Pu,Zr), γ-Pu, α-Pu, β-Pu, and ζ-Pu₂₈Zr phases in Pu-enriched region, when Pu concentrations exceed 75 at.% (equivalent to 89 wt% Pu). The compound θ-(Pu,Zr) has been said to occur at about 20 at.% Zr, but the regions for θ-(Pu,Zr) on the Pu-rich side have not been well defined. In an effort to understand the phases formed in Pu-Zr binary alloys and define the boundary between θ-(Pu,Zr), (θ+δ), and δ-(Pu,Zr) regions, Pu-10Zr (in wt.%, equivalent 23 at.%) alloys were scrutinized in this contribution. This manuscript details microstructural characterization and phase identification results obtained using electron microscopy-based techniques for a Pu-10Zr alloy before and after annealing at 550 °C. In contradiction with predicted phase diagrams, no θ-(Pu,Zr) was detected in any of the examined specimens. The phases present in as-cast fuel included a δ-(Pu,Zr) matrix with a number of smaller, randomly distributed α-Zr, ZrO₂, Zr₃O, PuO, and κ-PuZr₂ inclusions. Heat treatment annealed out the intermetallic κ-PuZr₂ phase and resulted in formation of small δ′-Pu and β-Pu inclusions. Similar to the as-cast alloys, the matrix of the annealed alloys was consistent with δ-(Pu,Zr) phase and contained small α-Zr, ZrO₂, and PuO₂ inclusions. Two different microscopy-based techniques were used for phase identification, but neither identified any θ-(Pu,Zr) phase. Differential scanning calorimetry was then used to determine the phase transition temperatures and enthalpies of transition for the identified phases. While our data is similar to the existing phase diagrams, a number of discrepancies are reported that call for a careful re-examination of the Pu-Zr system. This contribution discusses different scenarios that could explain the discrepancies between obtained and historical data, and provides the most logical conclusion that could be reached based on the obtained results.

Original language	English
Pages (from-to)	80-90
Number of pages	11
Journal	Journal of Nuclear Materials
Volume	523
DOIs	https://doi.org/10.1016/j.jnucmat.2019.05.051
State	Published - Sep 2019
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. The EBSD data collection and analysis was supported as part of a Nuclear Science User Facilities (NSUF) project. Fidelma Di Lemma would like to acknowledge NSUF scientist program funds, James Madden, and Daniel Murray for the help with EBSD data acquisition. 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.

Funders	Funder number
Fuel Cycle Research and Development
U.S. Department of Energy
Office of Nuclear Energy	DE-AC07-05ID14517
Laboratory Directed Research and Development

Keywords

Metallic fuel
Microstructure
Phase identification
Phase transition temperatures
Plutonium-zirconium

Access to Document

10.1016/j.jnucmat.2019.05.051

Cite this

@article{5fa7c0b7aead4e20aa65f41c091018bb,

title = "Microstructural characterization of the as-cast and annealed Pu-10Zr alloy",

abstract = "Phase diagrams constructed for the Pu-Zr binary system report the existence of θ-(Pu,Zr), δ-(Pu,Zr), γ-Pu, α-Pu, β-Pu, and ζ-Pu28Zr phases in Pu-enriched region, when Pu concentrations exceed 75 at.% (equivalent to 89 wt% Pu). The compound θ-(Pu,Zr) has been said to occur at about 20 at.% Zr, but the regions for θ-(Pu,Zr) on the Pu-rich side have not been well defined. In an effort to understand the phases formed in Pu-Zr binary alloys and define the boundary between θ-(Pu,Zr), (θ+δ), and δ-(Pu,Zr) regions, Pu-10Zr (in wt.%, equivalent 23 at.%) alloys were scrutinized in this contribution. This manuscript details microstructural characterization and phase identification results obtained using electron microscopy-based techniques for a Pu-10Zr alloy before and after annealing at 550 °C. In contradiction with predicted phase diagrams, no θ-(Pu,Zr) was detected in any of the examined specimens. The phases present in as-cast fuel included a δ-(Pu,Zr) matrix with a number of smaller, randomly distributed α-Zr, ZrO2, Zr3O, PuO, and κ-PuZr2 inclusions. Heat treatment annealed out the intermetallic κ-PuZr2 phase and resulted in formation of small δ′-Pu and β-Pu inclusions. Similar to the as-cast alloys, the matrix of the annealed alloys was consistent with δ-(Pu,Zr) phase and contained small α-Zr, ZrO2, and PuO2 inclusions. Two different microscopy-based techniques were used for phase identification, but neither identified any θ-(Pu,Zr) phase. Differential scanning calorimetry was then used to determine the phase transition temperatures and enthalpies of transition for the identified phases. While our data is similar to the existing phase diagrams, a number of discrepancies are reported that call for a careful re-examination of the Pu-Zr system. This contribution discusses different scenarios that could explain the discrepancies between obtained and historical data, and provides the most logical conclusion that could be reached based on the obtained results.",

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

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

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

year = "2019",

month = sep,

doi = "10.1016/j.jnucmat.2019.05.051",

language = "English",

volume = "523",

pages = "80--90",

journal = "Journal of Nuclear Materials",

issn = "0022-3115",

publisher = "Elsevier",

}

TY - JOUR

T1 - Microstructural characterization of the as-cast and annealed Pu-10Zr alloy

AU - Aitkaliyeva, Assel

AU - Adkins, Cynthia A.

AU - Hirschhorn, Jacob

AU - McKinney, Casey

AU - Tonks, Michael R.

AU - Di Lemma, Fidelma Giulia

PY - 2019/9

Y1 - 2019/9

N2 - Phase diagrams constructed for the Pu-Zr binary system report the existence of θ-(Pu,Zr), δ-(Pu,Zr), γ-Pu, α-Pu, β-Pu, and ζ-Pu28Zr phases in Pu-enriched region, when Pu concentrations exceed 75 at.% (equivalent to 89 wt% Pu). The compound θ-(Pu,Zr) has been said to occur at about 20 at.% Zr, but the regions for θ-(Pu,Zr) on the Pu-rich side have not been well defined. In an effort to understand the phases formed in Pu-Zr binary alloys and define the boundary between θ-(Pu,Zr), (θ+δ), and δ-(Pu,Zr) regions, Pu-10Zr (in wt.%, equivalent 23 at.%) alloys were scrutinized in this contribution. This manuscript details microstructural characterization and phase identification results obtained using electron microscopy-based techniques for a Pu-10Zr alloy before and after annealing at 550 °C. In contradiction with predicted phase diagrams, no θ-(Pu,Zr) was detected in any of the examined specimens. The phases present in as-cast fuel included a δ-(Pu,Zr) matrix with a number of smaller, randomly distributed α-Zr, ZrO2, Zr3O, PuO, and κ-PuZr2 inclusions. Heat treatment annealed out the intermetallic κ-PuZr2 phase and resulted in formation of small δ′-Pu and β-Pu inclusions. Similar to the as-cast alloys, the matrix of the annealed alloys was consistent with δ-(Pu,Zr) phase and contained small α-Zr, ZrO2, and PuO2 inclusions. Two different microscopy-based techniques were used for phase identification, but neither identified any θ-(Pu,Zr) phase. Differential scanning calorimetry was then used to determine the phase transition temperatures and enthalpies of transition for the identified phases. While our data is similar to the existing phase diagrams, a number of discrepancies are reported that call for a careful re-examination of the Pu-Zr system. This contribution discusses different scenarios that could explain the discrepancies between obtained and historical data, and provides the most logical conclusion that could be reached based on the obtained results.

AB - Phase diagrams constructed for the Pu-Zr binary system report the existence of θ-(Pu,Zr), δ-(Pu,Zr), γ-Pu, α-Pu, β-Pu, and ζ-Pu28Zr phases in Pu-enriched region, when Pu concentrations exceed 75 at.% (equivalent to 89 wt% Pu). The compound θ-(Pu,Zr) has been said to occur at about 20 at.% Zr, but the regions for θ-(Pu,Zr) on the Pu-rich side have not been well defined. In an effort to understand the phases formed in Pu-Zr binary alloys and define the boundary between θ-(Pu,Zr), (θ+δ), and δ-(Pu,Zr) regions, Pu-10Zr (in wt.%, equivalent 23 at.%) alloys were scrutinized in this contribution. This manuscript details microstructural characterization and phase identification results obtained using electron microscopy-based techniques for a Pu-10Zr alloy before and after annealing at 550 °C. In contradiction with predicted phase diagrams, no θ-(Pu,Zr) was detected in any of the examined specimens. The phases present in as-cast fuel included a δ-(Pu,Zr) matrix with a number of smaller, randomly distributed α-Zr, ZrO2, Zr3O, PuO, and κ-PuZr2 inclusions. Heat treatment annealed out the intermetallic κ-PuZr2 phase and resulted in formation of small δ′-Pu and β-Pu inclusions. Similar to the as-cast alloys, the matrix of the annealed alloys was consistent with δ-(Pu,Zr) phase and contained small α-Zr, ZrO2, and PuO2 inclusions. Two different microscopy-based techniques were used for phase identification, but neither identified any θ-(Pu,Zr) phase. Differential scanning calorimetry was then used to determine the phase transition temperatures and enthalpies of transition for the identified phases. While our data is similar to the existing phase diagrams, a number of discrepancies are reported that call for a careful re-examination of the Pu-Zr system. This contribution discusses different scenarios that could explain the discrepancies between obtained and historical data, and provides the most logical conclusion that could be reached based on the obtained results.

KW - Metallic fuel

KW - Microstructure

KW - Phase identification

KW - Phase transition temperatures

KW - Plutonium-zirconium

UR - http://www.scopus.com/inward/record.url?scp=85066636790&partnerID=8YFLogxK

U2 - 10.1016/j.jnucmat.2019.05.051

DO - 10.1016/j.jnucmat.2019.05.051

M3 - Article

AN - SCOPUS:85066636790

SN - 0022-3115

VL - 523

SP - 80

EP - 90

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

ER -

Microstructural characterization of the as-cast and annealed Pu-10Zr alloy

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this