Elucidation of chemical stability and interaction of waste elements for the creation of liquid transmutation targets

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K14560
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Tohoku University
• Principal Investigator: Shishido Hiroki 東北大学, 工学研究科, 助教 (90827792)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 溶融塩 / 核変換 / 核分裂生成物 / 電子状態 / 電気化学 / 分子動力学法 / 密度汎関数理論 / Flinabe

Outline of Final Research Achievements

We have proposed a molten salt-based nuclear transmutation target for transmitting high-level waste from nuclear power plants. It is necessary to clarify the interaction between long-lived fission products and molten salt solvents and to establish a methodology to evaluate chemical stability and physical properties for developing the transmutation target. This study evaluated the physical properties and redox potential of the fluoride molten salts and long-lived fission products as solvents using molecular dynamics simulation. We have revealed the effect of fission product elements on the viscosity formation in the BeF2 molten salt mixture. We have attempted to predict the redox potential of fission products in molten fluoride salts using first-principles calculations. The results showed that it is possible to evaluate the redox potential of fission products, although some accuracy issues remain.

Free Research Field

溶融塩工学

Academic Significance and Societal Importance of the Research Achievements

三元系混合塩LiF-NaF-BeF2の物性を数値解析により予測可能であることを示した。これら物性の中でも特に実験測定が困難である熱伝導率に対し、当該混合塩の熱伝導率はカチオンの電荷の非対称性のため既存のスケーリング則からは外れることを示した。また、ZrF4のような共有結合性の強いフッ化物はBeと同様にFイオンと強く結びつくため、BeF2に対する粘度低減の寄与が小さいことを明らかとした。LiFのようなイオン結合性が強いフッ化物が粘度低減の効果は大きく、長寿命核分裂生成物の中ではCsFが粘度低減に寄与する可能性が示唆される。本知見は溶融塩核変換ターゲットの材料設計において指針を与えるものである。