Evaluation of the Impact of Core Power Distribution on Reflooding Phenomenon in CCTF Test

The cylindrical core test facility (CCTF) is taken as the research object, optimal estimation program for transient behavior of LWR cooling system under accident condition RELAP5 and autonomous core design and safety analysis program LOCUST are used to evaluate the impact of core power distribution on the reflooding phenomenon under CCTF C2-SH2 (Run54) test conditions. The research shows: ① The calculations, such as the pressure drop in the descending section and core and the steam mass flowrate at the outlet of the code, provide good agreement with the test results; ② For the calculation of the average channel cladding peak temperature at 1.015 m of the core, the cladding peak temperatures calculated by RELAP5 and LOCUST programs are 816 K and 813 K respectively, the test results are 898 K, the calculated value is about 82 K lower than the test value, and the average channel cladding temperature finally stabilized at about 400 K. The calculated results are consistent with the test results. Therefore, the results of this study show that the LOCUST program can better simulate the transient process of the reflooding phase in the large-break loss-of-coolant accident (LBLOCA).