Model application research for liquid entrainment through ADS-4 pipe in AP1000

Application research of two new liquid entrainment models for separately predicting the beginning of entrainment and branch entrainment quality is performed which is a continuation of previous experimental and theoretical studies on the entrainment at T-junction. The new onset entrainment model and branch quality model are developed on the basis of the scaling experiment for studying ADS-4 entrainment phenomenon in AP1000 plant, and the two new models along with previously published entrainment models are compared. The results show that previous models in the background of entrainment through a small break of primary pipe are not suitable for predicting the entrainment through a large size branch (e.g. ADS-4 pipe), while the two new models have a larger applicability. Also, the new entrainment models are written into the RELAP5 code, and then a typical 2-in SBLOCA transient in AP1000 is simulated separately by the modified RELAP5 and the original RELAP5 to further discuss the applicability of new models for the simulation of entrainment through ADS-4. The results show that the modified RELAP5 can get more reasonable simulation results. In view of original RELAP5 overestimated core coolant inventory, the modified RELAP5 can get a conservative core coolant inventory. Hence we can conclude that the new entrainment models are more suitable for the simulation of entrainment through ADS-4.