Study theoretically on two-phase circulation flow characteristics under ERVC condition in advanced PWR

摘要

For the problem of two-phase natural circulation flow in gap clearance between reactor vessel lower head and insulator in the condition of severe accident, one-dimensional steady-state natural flow analysis code was written by utilizing FORTRAN. Based on the code, the effects of different correlations for friction coefficient and the number of nodes of heating section on mass flow rate of two-phase natural circulation flow were studied. And the results are compared with that of Chinese REPEC experiment and simulation using RELAP5 program so as to verify the rationality and correctness of the code. Based on the experiment data, simulation results and the model, friction coefficient and the void fraction condition under ERVC correlation are obtained by fitting. The results calculated by the model using fitting friction coefficient correlation agree well with ULPU V test data. Furthermore, the effect of power, pressure, inlet area, gap diameter, flooding level and inlet water subcooling on mass flow rate and void fraction of two-phase natural circulation were studied utilizing this code.