Abstract: [Background] The cooling liquid film is very important during the depressurization and cooling down process of the passive containment cooling system (PCS) which is part of the passive reactor safety design. [Purpose] This study aims to analyze the main heat transfer phenomenon in PCS overall response process during loss of coolant accident (LOCA) accident and to verify the design liquid film coverage safety margin. [Methods] The calculating model of integral test facility and PCS prototype were established respectively using passive containment safety analysis code. Based on scaling analysis, the ∏ (similarity number) related to heat transfer in containment and the ∏ ratio between test facility and prototype were obtained in both base and severe accident condition. The importance degrees of different heat transfer modes affecting the containment cooled down were compared, and the heat transfer distortion was assessed. [Results] After the cooling liquid film was established, the break energy was mainly carried out by steam condensation inner shell and the liquid evaporation outer shell. The condensation and evaporation phenomenon was simulated accurately in the containment integral test. [Conclusion] Since the energy absorbed by heat sinks is tiny, its relatively large heat transfer distortion could be neglected. The assessment of heat transfer phenomenon scaling distortion show that the integral test facility could simulate heat transfer process of PCS prototype in low liquid film coverage condition effectively.

Key words: PCS, Liquid film coverage, Scaling analysis, Heat transfer phenomenon, Distortion assessment