A numerical model for analyses of reflooding phase of a LOCA

A Computer program entitled QUEN1D is developed for analyses of the reflooding phase of a LOCA in a PWR. The physical model consists of a finite vertical fuel rod whose initial surface temperature distribution is similar to a chopped cosine form. During reflooding, six different flow regions are assumed to exist. Temperature history of cladding is obtained by solving one-dimensional heat conduction equation. Heat transfer coefficients and flow characteristics for various regions are determined by solving the mass and energy conservation equations for two-phase flow with the assumption of idealized separated flow along with well-known heat transfer correlations and flow transition criteria. To examine the applicability of QUEN1D, results of analyses are compared with the PWR-FLECHT data and predictions of the existing code