Impact of organic acids and carbonate ions on nuclide dissolution from fuel debris

2023 Fiscal Year Final Research Report

• Project/Area Number: 20H02665
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Kyoto University
• Principal Investigator: Sasaki Takayuki 京都大学, 工学研究科, 教授 (60314291)
• Co-Investigator(Kenkyū-buntansha): 桐島 陽 東北大学, 多元物質科学研究所, 教授 (00400424) ; 秋山 大輔 東北大学, 多元物質科学研究所, 講師 (80746751)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 燃料デブリ / 東京電力福島第一原子力発電所 / 有機酸 / 炭酸 / 溶解挙動

Outline of Final Research Achievements

The chemical resistance of simulated debris to water containing organic acids and carbonic acid was investigated to consider a more realistic and feasible method for the final disposal of fuel debris w/o applying excessively conservative pretreatment. The dissolution process was evaluated thermodynamically. Focusing on the uranium-zirconium solid solutions, the uranium-iron oxide, and the uranium-calcium oxide as the simulated fuel debris, we conducted the dissolution experiment in the presence of dicarboxylic acid and/or carbonate, and analyzed the solid phase conditions and the dissolved species using various spectroscopic methods. Nuclide concentrations and dissolution rates increased with the organic acid and carbonate concentrations. Then, a new steady state between solid and liquid phases was reached due to forming a secondary solid phase on the debris surface with a redox reaction.

Free Research Field

バックエンド工学

Academic Significance and Societal Importance of the Research Achievements

本研究は、福島第一原発事故で発生したと考えられる代表的なウラン燃料デブリやその関連物質を実験室で模擬合成し、地上地下の天然水に普遍的に含まれる有機酸や炭酸を含む水に対する化学的耐性、すなわち核種の溶解反応と溶解前後のデブリ表面の化学状態変化について実験的に評価した。この基礎知見は、進行中の廃炉事業において回収が計画されているデブリの、過度に保守的でないより安全で合理的な処理処分方策の立案に有益な情報をもたらすものである。