Heat conduction analyses on rewetting front propagation during transients beyond anticipated operational occurrences for BWRs

与能本 泰介; 柴本 泰照; 佐藤 聡; 岡垣 百合亜

Journal of Nuclear Science and Technology, 53(9), p.1342 - 1352, 2016/09

AA2015-0497.pdf:1.05MB

https://doi.org/10.1080/00223131.2015.1108882

BWRの運転時の異常な過渡変化を超える過渡事象におけるドライアウトした燃料表面のリウェット挙動に関して、当研究グループで以前実施した研究では、リウェット直前の冷却として定義する先行冷却により、その伝播速度が強く支配されることが示された。本研究では、この先行冷却の特徴を把握するために、実験結果に対して、さらに工学解析と熱伝導解析を実施した。特徴把握のため、まず、先行冷却を熱伝達率評価値を用いて定量的に定義し、先行冷却が開始するタイミングでの被覆管温度の関数としてリウェット速度を検討した。その結果、リウェット点近傍での最大伝熱量によりリウェット速度が制限される傾向が示され、熱伝導解析の結果と整合した。

Evaluation of liquid film front behavior during rewetting process based on visualization experiment

Le, T. D.; 和田 裕貴; 柴本 泰照; 与能本 泰介

no journal, , 

A rewetting phenomenon by liquid film propagation is one of key factors to evaluate peak cladding temperature and dryout duration after the occurrence of the post-boiling transition. The AESJ (2003) proposed the empirical correlation to predict the rewetting velocity in the anticipated operational occurrence conditions, which was recently applied to the evaluation of fuel rod surface temperature during an anticipated transient without scram for the safety review on the Japanese new regulation. Our previous studies have indicated the propagation velocity of the rewetting front is significantly affected by the heat transfer in the dried region immediately before the rewetting front, which is defined as precursory cooling (PC). The mechanism of the PC is still not clarified because of insufficient related studies. Therefore, this study visually investigates liquid film front behavior on a single heater pin surface with air-water flow at atmospheric pressure. Results showed oscillatory formation of dry patches in the liquid film in the vicinity of the rewetting front. This oscillation continued until the heated rod was completely cooled.