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Title: Isochronal Annealing Studies in Pu and Pu Alloys Using Magnetic Susceptibility

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [2]
  1. Lawrence Livermore National Laboratory (LLNL)
  2. {Dick} G [ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
930927
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Alloys and Compounds; Journal Volume: 444; Journal Issue: 0
Country of Publication:
United States
Language:
English

Citation Formats

McCall, S. K., Fluss, M. J., Chung, B. W., McElfresh, M. W., Chapline, G.F., Jackson, D. D., and Haire, Richard. Isochronal Annealing Studies in Pu and Pu Alloys Using Magnetic Susceptibility. United States: N. p., 2007. Web. doi:10.1016/j.jallcom.2006.12.090.
McCall, S. K., Fluss, M. J., Chung, B. W., McElfresh, M. W., Chapline, G.F., Jackson, D. D., & Haire, Richard. Isochronal Annealing Studies in Pu and Pu Alloys Using Magnetic Susceptibility. United States. doi:10.1016/j.jallcom.2006.12.090.
McCall, S. K., Fluss, M. J., Chung, B. W., McElfresh, M. W., Chapline, G.F., Jackson, D. D., and Haire, Richard. Mon . "Isochronal Annealing Studies in Pu and Pu Alloys Using Magnetic Susceptibility". United States. doi:10.1016/j.jallcom.2006.12.090.
@article{osti_930927,
title = {Isochronal Annealing Studies in Pu and Pu Alloys Using Magnetic Susceptibility},
author = {McCall, S. K. and Fluss, M. J. and Chung, B. W. and McElfresh, M. W. and Chapline, G.F. and Jackson, D. D. and Haire, Richard},
abstractNote = {},
doi = {10.1016/j.jallcom.2006.12.090},
journal = {Journal of Alloys and Compounds},
number = 0,
volume = 444,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The isochronal annealing of the low temperature accumulated damage from the radioactive decay of plutonium in {alpha}-Pu, {delta}-Pu{sub 1-x}Ga{sub x} (x = 0.043) and {delta}-Pu{sub 1-x}Am{sub x} (x = 0.224) was characterized using magnetic susceptibility. In each specimen, thermal annealing, as tracked by magnetic susceptibility, only commenced when T > 33 K and the magnetic susceptibility changes due to defects were fully annealed at T not, vert, similar 300 K. The {alpha}-Pu magnetic susceptibility isochronal annealing data is similar to earlier measurements of resistivity characterized isochronal annealing. However, the {delta}-Pu{sub 1-x}Ga{sub x} (x = 0.043) magnetic susceptibility isochronal annealing data,more » when compared with similar resistivity data, indicates that for this alloy magnetic susceptibility studies are more sensitive to vacancies than to the interstitials accumulated at low temperatures. The Pu{sub 1-x}Am{sub x} (x = 0.224) alloy shows a remarkable change in properties, over a limited temperature range beginning where interstitial defects are first mobile, and characterized by an induced effective moment of order 1.1 {mu}{sub B}/Pu. This transient behavior may be evidence for a disorder driven low temperature phase transition, perhaps indicative of a compositional and structural proximity to a state possessing significant magnetic moments.« less
  • Results of radiation damage in Pu and Pu{sub 1-x}Am{sub x} alloys studied with magnetic susceptibility, {chi}(T), and resistivity are presented. Damage accumulated at low temperatures increases {chi}(T) for all measured alloys, with the trend generally enhanced as the lattice expands. There is a trend towards saturation observable in the damage induced magnetic susceptibility data, that is not evident in similar damage induced resistivity data taken on the same specimen. A comparison of isochronal annealing curves measured by both resistivity and magnetic susceptibility on a 4.3at% Ga stabilized {delta}-Pu specimen show that Stage I annealing, where interstitials begin to move, ismore » largely transparent to the magnetic measurement. This indicates that interstitials have little impact on the damage induced increase in the magnetic susceptibility. The isochronal annealing curves of the Pu{sub 1-x}Am{sub x} alloys do not show distinct annealing stages as expected for alloys. However, samples near 20% Am concentration show an unexpected increase in magnetization beginning when specimens are annealed to 35K. This behavior is also reflected in a time dependent increase in the magnetic susceptibility of damaged specimens indicative of first order kinetics. These results suggest there may be a metastable phase induced by radiation damage and annealing in Pu{sub 1-x}Am{sub x} alloys.« less
  • Results of radiation damage in Pu and Pu{sub 1-x}Am{sub x} alloys studied with magnetic susceptibility, {chi}(T), and resistivity are presented. Damage accumulated at low temperatures increases {chi}(T) for all measured alloys, with the trend generally enhanced as the lattice expands. There is a trend towards saturation observable in the damage induced magnetic susceptibility data. that is not evident in similar damage induced resistivity data taken on the same specimen. A comparison of isochronal annealing curves measured by both resistivity and magnetic susceptibility on a 4.3 at% Ga stabilized {delta}-Pu specimen show that Stage I annealing, where interstitials begin to move,more » is largely transparent to the magnetic measurement. This indicates that interstitials have little impact on the damage induced increase in the magnetic susceptibility. The isochronal annealing curves of the Pu{sub 1-x}Am{sub x} alloys do not show distinct annealing stages as expected for alloys. However, samples near 20% Am concentration show an unexpected increase in magnetization beginning when specimens are annealed to 35 K. This behavior is also reflected in a time dependent increase in the magnetic susceptibility of damaged specimens indicative of first order kinetics. These results suggest there may be a metastable phase induced by radiation damage and annealing in Pu{sub 1-x}Am{sub x} alloys. (authors)« less
  • The effects on the local structure due to self-irradiation damage of Ga stabilized δ-Pu stored at cryogenic temperatures have been examined using extended x-ray absorption fine structure (EXAFS) experiments. Extensive damage, seen as a loss of local order, was evident after 72 days of storage below 15 K. The effect was observed from both the Pu and the Ga sites, although less pronounced around Ga. Isochronal annealing was performed on this sample to study the annealing processes that occur between cryogenic and room temperature storage conditions, where damage is mostly reversed. Damage fractions at various points along the annealing curve havemore » been determined using an amplitude-ratio method, a standard EXAFS fitting, and a spherical crystallite model, and provide information complementary to the previous electrical resistivity- and susceptibility-based isochronal annealing studies. The use of a spherical crystallite model accounts for the changes in EXAFS spectra using just two parameters, namely, the crystalline fraction and the particle radius. Together, these results are discussed in terms of changes to the local structure around Ga and Pu throughout the annealing process and highlight the unusual role of Ga in the behavior of the lowest temperature anneals.« less
  • The effects on the local structure due to self-irradiation damage of Ga stabilized δ-Pu stored at cryogenic temperatures have been examined using extended x-ray absorption fine structure (EXAFS) experiments. Extensive damage, seen as a loss of local order, was evident after 72 days of storage below 15 K. The effect was observed from both the Pu and the Ga sites, although less pronounced around Ga. Isochronal annealing was performed on this sample to study the annealing processes that occur between cryogenic and room temperature storage conditions, where damage is mostly reversed. Damage fractions at various points along the annealing curvemore » have been determined using an amplitude-ratio method, a standard EXAFS fitting, and a spherical crystallite model, and provide information complementary to the previous electrical resistivity- and susceptibility-based isochronal annealing studies. The use of a spherical crystallite model accounts for the changes in EXAFS spectra using just two parameters, namely, the crystalline fraction and the particle radius. Altogether, these results are discussed in terms of changes to the local structure around Ga and Pu throughout the annealing process and highlight the unusual role of Ga in the behavior of the lowest temperature anneals.« less