Evaluation of tritium inventory in the vacuum vessel of fusion reactor by modeling the irradiation defects transport behaviors

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K13903
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 14020:Nuclear fusion-related
• Research Institution: National Institute for Fusion Science
• Principal Investigator: Kobayashi Makoto 核融合科学研究所, 研究部, 助教 (50791258)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 照射損傷 / 中性子 / 水素同位体

Outline of Final Research Achievements

A calculation code to estimate the time evolution of a concentration of irradiation defect clusters in tungsten has been developed to predict the tritium inventory in fusion reactor. The model in the code was based on rate theory, taking account of various transport processes of defect clusters. The these kinetics, while increasing the size of clusters, could be estimated by an empirical physics model.
A benchmark test for 6.4 MeV Fe ion irradiation and 20 MeV W ion irradiation was conducted, comparing the depth profile of vacancy concentration in tungsten evaluated by the developed code to that of deuterium which decorating vacancies reported in literature. The estimated depth profile of vacancy cluster concentration in tungsten was consistent with that of deuterium. In near-saturation conditions of deuterium decoration in vacancies, the deuterium-vacancy ratio was estimated to be about 6, agreeing with previous theoretical studies of hydrogen trapping capacity in a vacancy well.

Free Research Field

核融合炉工学

Academic Significance and Societal Importance of the Research Achievements

核融合炉真空容器には放射性物質であるトリチウムが蓄積し、真空喪失などの事故時に放出することが予測されるため、トリチウム蓄積量と正確に予測することで事故リスクの評価が初めて可能になる。本研究で開発した計算コードは核融合炉の運転に伴い劇的に変化するトリチウム蓄積量を定量評価可能とするものであるため、核融合炉の社会実装に大きく貢献できる成果と考える。
さらに、固体中の欠陥蓄積は原子炉材料や宇宙材料などとも共通の課題であり、それを精度よく予測できる技術は様々な波及効果もあり、学術的にも意義の大きい研究であると考えている。