Compositional control of radionuclide retention in hollandite‐based ceramic waste forms for Cs‐immobilization

Journal Article · Mon Dec 31 00:00:00 EST 2018 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/jace.16258· OSTI ID:1508181

Zhao, Mingyang ^[1]; Xu, Yun ^[1]; Shuller‐Nickles, Lindsay ^[2]; Amoroso, Jake ^[3]; Frenkel, Anatoly I. ^[4]; Li, Yuanyuan ^[5]; Gong, Weiping ^[6]; Lilova, Kristina ^[6]; Navrotsky, Alexandra  ^[6]; Brinkman, Kyle S.  ^[7]

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1. Department of Materials Science and Engineering Clemson South Carolina
2. Department of Environmental Engineering and Earth Sciences Clemson South Carolina, Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management (NEESRWM) Clemson University Clemson South Carolina
3. Savannah River National Laboratory Aiken South Carolina
4. Department of Materials Science and Chemical Engineering Stony Brook University Stony Brook New York, Division of Chemistry Brookhaven National Laboratory Upton New York
5. Department of Materials Science and Chemical Engineering Stony Brook University Stony Brook New York
6. Peter A. Rock Thermochemistry Laboratory and NEAT ORU University of California Davis Davis Carolina
7. Department of Materials Science and Engineering Clemson South Carolina, Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management (NEESRWM) Clemson University Clemson South Carolina

Abstract Hollandite materials, as a class of crystalline nuclear waste forms, are promising candidates for the immobilization of radioactive elements, such as Cs, Ba, as well as a variety of lanthanide and transition‐metal fission products. In this study, three Ga‐doped titanate hollandite‐type phases, Ba _1.33 Ga _2.67 Ti _5.33 O ₁₆ , Ba _0.667 Cs _0.667 Ga ₂ Ti ₆ O ₁₆ , and Cs _1.33 Ga _1.33 Ti _6.67 O ₁₆ , were synthesized using a solid‐state reaction route. All synthesized phases adopted a single phase tetragonal structure, as determined by powder X‐ray diffraction ( XRD ), and elemental analysis confirmed the measured stoichiometries were close to targeted compositions. Extended X‐ray absorption fine structure spectroscopy ( EXAFS ) was used to determine the local structural features for the framework of octahedrally coordinated cations. EXAFS data indicated that Cs _1.33 Ga _1.33 Ti _6.67 O ₁₆ possessed the most disordered local structure centered around the Ga dopant. The enthalpies of formation of all three hollandite phases measured using high‐temperature oxide melt solution calorimetry were found to be negative, indicating enthalpies of formation of these hollandites from oxides are thermodynamically stable with respect to their constituent oxides. Furthermore, the formation enthalpies were more negative and hence more favorable with increased Cs content. Finally, aqueous leaching tests revealed that high Cs content hollandite phases exhibited greater Cs retention as compared to low Cs content hollandite. While preliminary in nature, this work draws attention to the links between the capacity for radionuclide retention, atomistic level structural features and bulk thermodynamic properties of materials.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DE‐ SC0012530; DE‐FG02‐03ER15476; DE‐SC0001089; DE‐SC0016574; DE‐AC09‐08SR22470
• OSTI ID: 1508181
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Vol. 102 Journal Issue: 7; ISSN 0002-7820
• Publisher: Wiley-Blackwell
• Country of Publication: United States
• Language: English