잔열제거계통 배관에서의 열성층 현상에 관한 연구

Numerical study is carried out for thermal stratification on residual heat removal piping connected with RCS piping of NPP. The turbulent penetration length reaches to 1^st isolation valve. Thermal stratification mainly occurs in the horizontal piping connected with elbow. The maximum temperature difference occurs in the location where horizontal piping starts passing elbow. The temperature difference between upper and lower of horizontal piping changes with valve leak, curve radius of elbow, pipe thick and connection of hotleg injection line. Thermal stratification effect in the backward of 1^st valve is small when piping thick is not considered and when valve is isolated, but is large when piping thick is considered or when valve leaks.