Heat Transfer Degradation under irradiation environment

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H02645
• 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: The University of Tokyo
• Principal Investigator: Okamoto Koji 東京大学, 大学院工学系研究科(工学部), 教授 (80204030)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 限界熱流束 / 伝熱劣化 / 照射効果 / 原子力安全 / 放射線

Outline of Final Research Achievements

Heat transfer characteristics had been affected by the irradiation. The CHF (Critical Heat Flux) experiment had been carried out using the silver surface, aluminum surface and carbon steel surface, irradiated by gamma-ray and electron-beam. The image processing and boiling curve had been evaluated to understand the CHF. The CHF may occur under the boiling bubble covering the heating surface. Nucleate site had been affected by the irradiated oxidized surface. Then, the bubble generation with many nucleate site causes the coverage of heating surface, resulting in the heat transfer degradation. The microscopic characteristics of irradiated oxidized surface has strong relation to macroscopic heat transfer characteristics.

Free Research Field

原子力工学

Academic Significance and Societal Importance of the Research Achievements

材料表面の酸化被膜の性状により、放射線照射による伝熱性能が影響を受けることを明らかとした。特に、銀やアルミにおいては、酸化被膜に電子線またはガンマ線が照射されると、ミクロな沸騰核に影響を及ぼし、結果として沸騰伝熱に影響を与えることが明らかとなった。特に限界熱流束など、安全性に影響のある伝熱性能においては、放射線によるミクロな酸化被膜の状態変化が、マクロな沸騰現象に影響を与えることを明らかとした。伝熱劣化は炭素鋼では観測されず、実機においては安全性には大きな影響を与えない可能性がある。