Computational Scientific Study on Mechanism of Multiphase Thermal-Hydraulic Phenomena Related to IVR in Core Disruptive Accidents

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04944
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Kyushu University
• Principal Investigator: Morita Koji 九州大学, 工学研究院, 教授 (40311849)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 高速炉 / 過酷事故 / 炉心損傷事故 / 計算科学 / 粒子法 / 多相流 / 熱流動

Outline of Final Research Achievements

To clarify thermal-hydraulic phenomena that are important for achieving in-vessel retention (IVR) of core materials during severe accidents in fast reactors, a 3D thermal-hydraulic analysis code based on a computational science method (particle method) that can analyze multi-component multiphase flow behavior with heat transfer, convection, and phase changes with high accuracy has been developed as a fundamental technology. From the fast reactor safety tests conducted so far, "heat transfer behavior from the molten fuel pool to the structural wall" and "erosion behavior of the structural wall due to jet impingement" were selected as important dominant phenomena related to IVR, and 3-D particle based simulations were conducted for these phenomena. As a result, the mechanism of thermal-hydraulic behavior involved in these dominant phenomena, which is difficult to analyze with high accuracy using conventional analytical techniques based on empirical models, was clarified.

Free Research Field

原子力工学

Academic Significance and Societal Importance of the Research Achievements

本研究は、高速炉の過酷事故を対象としたものであるが、計算科学的手法である粒子法を基盤とする数値シミュレーション技術は、他の原子炉における過酷事故の熱流動現象解析にも応用できることから、汎用性、適用性に優れた原子力分野における安全評価技術のイノベーションと位置づけられる。また、本研究により、原子炉の過酷事故において重要な熱流動現象について、支配因子の影響度を定量的に明確化し、安全評価の妥当性を確認するための新たな知見や裏付けを提供できる。これにより、過酷事故評価の信頼度を向上し、原子炉の安全論理の構築に資することが期待される。