Elastic moduli of $$\delta$$-Pu239 reveal aging in real time
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
We study the time evolution (aging) of the elastic moduli of an eight-year-old polycrystalline δ- Pu 2.0 at % Ga alloy (δ-Pu:Ga ) from 295K to nearly 500K in real time using Resonant Ultrasound Spectroscopy (RUS). After 8 years of aging at 295K, the bulk and shear moduli increase at a normalized rate of 0.2%/year and 0.6%/year respectively. As the temperature is raised, two time dependences are observed, an exponential one of about a week, followed by a linear one (constant rate). The linear rate is thermally activated with an activation energy of 0.33+0.06 eV. Above 420K a qualitative change in the time evolution is observed; the bulk modulus decreases with time while the shear modulus continues to stiffen. No change is observed as the α-β transition temperature is crossed as would be expected if a decomposition of δ-Pu:Ga to α-Pu and Pu3Ga occurred over the temperature range studied. Our results indicate that the main mechanism of aging is creation of defects that are partially annealed starting at T = 420 K.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC52-06NA25396; SC0001089; AC52-07NA27344
- OSTI ID:
- 1352421
- Alternate ID(s):
- OSTI ID: 1349003; OSTI ID: 1349383
- Report Number(s):
- LA-UR-16-28430; LLNL-JRNL-712781; TRN: US1700582
- Journal Information:
- Journal of Applied Physics, Vol. 121, Issue 12; ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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