COSINE is a self-reliant development code package of China which is a core and system integrated engine used for NPP’s design and analysis. cosCSLOCA is a sub-program among the thermal hydraulic design and safety analysis codes in COSINE software package. It is applicable to analyze the loss of coolant accidents(LOCA) in nuclear power plants and use the conservative models recommended in appendix K of NRC 10cfr50.46. And cosBELOCA is the loss of coolant accident best estimation analysis code which is also included in COSINE .

The Post-CHF heat transfer is an important phenomenon to predict the peak cladding temperature during a LOCA. This paper listed the correlations of Post-CHF heat transfer adopted in these two codes and introduced the flowchart of development in cosCSLOCA. In addition, the ORNL THTF tests have been used for the verification of the Post-CHF models in both cosCSLOCA and cosBELOCA. Comparisons are made between the experimental results, the results calculated by relap5/3.3, cosCSLOCA and cosBELOCA. The results show that the results of the three codes had the same trend with experiment, and the calculated cladding temperatures using cosCSLOCA are higher than cosBELOCA and relap5/3.3.Through the separate effect assessments, the conservative of the post-CHF heat transfer model in cosCSLOCA were verified.