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Study on the solubility and structure of actinide hydroxides and oxides

Research Project

Project/Area Number 16K18348
Research Category

Grant-in-Aid for Young Scientists (B)

Allocation TypeMulti-year Fund
Research Field Nuclear engineering
Research InstitutionKyoto University

Principal Investigator

Kobayashi Taishi  京都大学, 工学研究科, 准教授 (80630269)

Project Period (FY) 2016-04-01 – 2020-03-31
Project Status Completed (Fiscal Year 2019)
Budget Amount *help
¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
Fiscal Year 2019: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2017: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2016: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Keywords放射性廃棄物処分 / 4価金属イオン / 溶解度 / 構造解析 / 化学熱力学 / 粒子サイズ効果 / ジルコニウム / 水酸化物 / 酸化物 / 階層構造 / X線小角散乱 / ゼータ電位 / 水酸化物固相 / SAXS / XAFS / トリウム / 結晶子サイズ / アクチノイド / 粒子サイズ / 固液界面
Outline of Final Research Achievements

Under the geochemical conditions of radioactive waste disposal, migration behaviors of radionuclides with tetravalent oxidation state are primarily controlled by the solubilities of their amorphous hydroxides. The present study revealed that the amorphous hydroxides consisted of oligomeric polynuclear hydrolysis species, primary particles with approximately 3 nm in size, and their aggregates larger than 100 nm from the combined measurements of X-ray adsorption spectroscopy, small angle X-ray scattering, and X-ray diffraction. The solubility of the amorphous hydroxides and crystalline oxides were investigated as functions of pH and temperatures to discuss the solubility behavior from the thermodynamic point of view. It was then suggested that the primary particle in the hierarchal structure of tetravalent hydroxides and oxides controlled the apparent solubility.

Academic Significance and Societal Importance of the Research Achievements

従来の4価金属イオンの水酸化物や酸化物に関する溶解度研究では、バルク結晶構造の同定が中心であったが、本研究では異なる分析手法を組み合わせることで幅広い空間スケールにおける固相の構造を調べた。溶解度制限固相としての1次粒子の存在を新たに提案するなど研究成果の学術的な意義は大きい。また、4価金属イオンとして振る舞う放射性核種の溶解挙動は、既存の放射性廃棄物のみならず、福島事故によって発生した燃料デブリの安定性評価においても重要であり、燃料デブリの処理処分という社会的な課題解決に向けた貢献も少なくないと考えられる。

Report

(5 results)
  • 2019 Annual Research Report   Final Research Report ( PDF )
  • 2018 Research-status Report
  • 2017 Research-status Report
  • 2016 Research-status Report
  • Research Products

    (8 results)

All 2019 2018 2017

All Journal Article (2 results) (of which Int'l Joint Research: 1 results,  Peer Reviewed: 2 results) Presentation (6 results) (of which Int'l Joint Research: 3 results,  Invited: 1 results)

  • [Journal Article] Structural Approach to Understanding the Solubility of Metal Hydroxides2019

    • Author(s)
      T. Kobayashi, S. Nakajima, R. Motokawa, D. Matsumura, T. Saito, T. Sasaki
    • Journal Title

      Langmuir

      Volume: 35 Issue: 24 Pages: 7995-8006

    • DOI

      10.1021/acs.langmuir.9b01132

    • Related Report
      2019 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Solubilities and solubility products of thorium hydroxide under moderate temperature conditions2018

    • Author(s)
      S. Nishikawa, T. Kobayashi, T. Sasaki, I. Takagi
    • Journal Title

      Radiochimica Acta

      Volume: 106 Issue: 8 Pages: 655-668

    • DOI

      10.1515/ract-2017-2917

    • Related Report
      2018 Research-status Report 2017 Research-status Report
    • Peer Reviewed
  • [Presentation] 4価金属酸化物および水酸化物コロイドのゼータ電位と粒径分布の測定と解釈2019

    • Author(s)
      伏見朋和, 小林大志, 佐々木隆之, 元川竜平
    • Organizer
      日本放射化学会第63回討論会
    • Related Report
      2019 Annual Research Report
  • [Presentation] 4価アクチノイドの錯生成および溶解度に関する熱力学的研究2019

    • Author(s)
      小林大志
    • Organizer
      日本放射化学会第63回討論会
    • Related Report
      2019 Annual Research Report
    • Invited
  • [Presentation] STRUCTURE OF SOLUBILITY LIMITING SOLID PHASE IN Zr(IV) HYDROXIDE SYSTEMS UNDER ELEVATED TEMPERATURE2018

    • Author(s)
      T. Kobayashi, S. Nakajima, R. Motokawa, T. Saito, T. Sasaki
    • Organizer
      International Symposium on Solubility Phenomena and Related Equilibrium Processes
    • Related Report
      2018 Research-status Report
    • Int'l Joint Research
  • [Presentation] Zr水酸化物コロイドのゼータ電位の測定と熱力学的解釈2018

    • Author(s)
      伏見朋和, 小林大志, 佐々木隆之
    • Organizer
      原子力学会2018年秋の大会
    • Related Report
      2018 Research-status Report
  • [Presentation] Solubility Limiting Solid Phase in Zr(IV)/Th(IV) Hydroxide System under Elevated Temperature: Solubility and SWAXS Studies2017

    • Author(s)
      T. Kobayashi, S. Nakajima, S. Nishikawa, R. Motokawa, T. Saito, T. Sasaki
    • Organizer
      Migration 2017
    • Related Report
      2017 Research-status Report
    • Int'l Joint Research
  • [Presentation] SAXS study on temperature dependence of the solid phase transformation on the solubility of zirconium hydroxide2017

    • Author(s)
      S. Nakajima, T. Kobayashi, R. Motokawa, T. Saito, T. Sasaki
    • Organizer
      Actinides 2017
    • Related Report
      2017 Research-status Report
    • Int'l Joint Research

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Published: 2016-04-21   Modified: 2021-02-19  

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