Study on severe accidents of oxide-fueled sodium-cooled fast reactors, 1; Project overview and progress until 2025

Yamano, Hidemasa  ; Matsuba, Kenichi  ; Sasa, Kyohei*; Kinoshita, Enki*; Morita, Koji*; Saito, Yasushi*; Ito, Kei*; Suzuki, Toru*

A research project on severe accidents of oxide-fueled core has been started since 2024 as research and development in a conceptual design stage of demonstration sodium-cooled fast reactors in Japan. It is necessary to develop analytical methodologies and technical bases to confirm the effectiveness of various design measures, which are introduced to the demonstration reactor in order to achieve recriticality elimination and in-vessel retention. The project implements element testing, integral testing, analytical methodology development and reactor application analyses, in which involved are important phenomena of fuel discharge behavior, core residual fuel coolability, and debris-bed formation behavior and coolability. This paper describes the project overview and progress until 2025.