Bubble formation and lattice parameter changes resulting from He irradiation of defect-fluorite Gd₂Zr₂O₇

Journal Article · Mon Jun 06 00:00:00 EDT 2016 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2016.05.045· OSTI ID:1356957

Taylor, Caitlin A.  ^[1]; Patel, Maulik K. ^[1]; Aguiar, Jeffery A. ^[2]; Zhang, Yanwen ^[3]; Crespillo, Miguel L. ^[1]; Wen, Juan ^[4]; Xue, Haizhou ^[1]; Wang, Yongqiang ^[5]; Weber, William J. ^[6]

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1. Univ. of Tennessee, Knoxville, TN (United States). Department of Materials Science and Engineering
2. Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Performance and Design Department; National Renewable Energy Lab. (NREL), Golden, CO (United States). Material Science Center
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Univ. of Tennessee, Knoxville, TN (United States). Department of Materials Science and Engineering
4. Lanzhou Univ. (China). School of Nuclear Science and Technology; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
6. Univ. of Tennessee, Knoxville, TN (United States). Department of Materials Science and Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

We report that pyrochlores have long been considered as potential candidates for advanced ceramic waste-forms for the immobilization of radioactive waste nuclides. This work provides evidence that Gd₂Zr₂O₇, often considered the most radiation tolerant pyrochlore, could be susceptible to radiation damage in the form of bubble nucleation at the highest He doses expected over geological time. Ion irradiations were utilized to experimentally simulate the radiation damage and He accumulation produced by α-decay. Samples were pre-damaged using 7 MeV Au³⁺ to induce the pyrochlore to defect-fluorite phase transformation, which would occur due to α-recoil damage within several hundred years of storage in a Gd₂Zr₂O₇ waste-form. These samples were then implanted to various He concentrations in order to study the long-term effects of He accumulation. Helium bubbles 1–3 nm in diameter were observed in TEM at a concentration of 4.6 at.% He. Some bubbles remained isolated, while others formed chains 10–30 nm in length parallel to the surface. GIXRD measurements showed lattice swelling after irradiating pristine Gd₂Zr₂O₇ with 7 MeV Au³⁺ to a fluence of 2.2 × 10¹⁵ Au/cm². An increase in lattice swelling was also measured after 2.2 × 10¹⁵ Au/cm² + 2 × 10¹⁵ He/cm² and 2.2 × 10¹⁵ Au/cm² + 2 × 10¹⁶ He/cm². A decrease in lattice swelling was measured after irradiation with 2.2 × 10¹⁵ Au/cm² + 2 × 10¹⁷ He/cm², the fluence where bubbles and bubble chains were observed in TEM. Lastly, bubble chains are thought to form in order to reduce lattice strain normal to the surface, which is produced by the Au and He irradiation damage.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-00OR22725; AC52-06NA25396; AC04-94AL85000; NE0000693
• OSTI ID: 1356957
• Journal Information: Acta Materialia, Vol. 115, Issue C; ISSN 1359-6454
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
36 MATERIALS SCIENCE
Pyrochlore
Helium bubble
Radiation damage
Nuclear waste
Lattice swelling