Aging Effects on Curium-Doped Titanate Ceramic Containing Sodium-Bearing High-Level Nuclear Waste

Authors

  • Hisayoshi Mitamura,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Member, American Ceramic Society.

    • *

      Department of Environmental Safety Research, Japan Atomic Energy Research Institute.

  • Seiichiro Matsumoto,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Department of Hot Laboratories, Japan Atomic Energy Research Institute.

  • Kaye P. Hart,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Australian Nuclear Science and Technology Organisation.

  • Takashi Miyazaki,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • §

      Chiyoda Maintenance Ltd.

  • Eric R. Vance,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Member, American Ceramic Society.

    • Australian Nuclear Science and Technology Organisation.

  • Yukito Tamura,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Member, American Ceramic Society.

  • Yoshihiro Togashi,

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Department of Hot Laboratories, Japan Atomic Energy Research Institute.

  • Timothy J. White

    1. Department of Environmental Safety Research and Department of Hot Laboratories, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki, 319–11, Japan; Advanced Materials Program, Australian Nuclear Science and Technology Organisation, Lucas Heights Research Laboratories, Lucas Heights, N.S.W., Australia; Second Department of Nuclear Business, Ibaraki Center, Chiyoda Maintenance Ltd., Asahi, Kashima, Ibaraki 314–14, Japan; Electron Microscope Centre, University of Queensland, St. Lucia, Brisbane 4067, Australia
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    • Member, American Ceramic Society.

    • University of Queensland.


  • C. Jantzen—contributing editor

Abstract

Curium-doped titanate ceramic containing sodium-rich high-level nuclear waste showed a gradual decrease in density up to a dose of 8.5 × 1017α decays ·g−1. After that, the rate of density change increased apparently because of crack formation. Optical microscopy showed cracks >0.1 mm long and > 1 μm wide after a dose of 7.9 × 1017α decays ·g−1. Leach tests suggested that the dissolution-control phases for sodium and cesium changed from freudenbergite and hollandite, respectively, to intergranular phases after significant cracking. Aging also enhanced strontium losses, relative to calcium, indicating that strontium may also be partitioned to the intergranular phases. After the fresh surfaces produced by cracking were exposed to leachant, and the dissolution of soluble intergranular surfaces was complete, the leaching of nonradioactive elements from the samples having a dose of 12.3 × 1017α decays ·g−1 was limited by the following dissolution-control phases: freudenbergite (Na), hollandite (Cs and Ba), perovskite and/or zirconolite (Sr and Ca), and alloys (Mo). The leaching behavior of the nonradioactive indicator elements revealed that chemical durability was reduced by two main factors: (1) increasing the effective surface area by crack formation and (2) decreasing the stability of the actinide-host phases by α-recoil damage. In combination these factors increased longer-term (>7 days) leach rates of sodium and cesium, and strontium and calcium by 1 and 2 orders of magnitude, respectively. In spite of deterioration of the actinide-host phases, the curium leach rate after a dose of 12.3 × 1017α decays x g−1 decreased by 2 orders of magnitude, possibly as a result of precipitation of curium hydrolysis products.

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