REFLOD3B: A computer code simulating PWR system behavior during reflood

The REFLOD3B computer code was developed by the Babcock ampersand Wilcox (B ampersand W) Fuel Company to calculate the system behavior of a pressurized water reactor (PWR) during the refill and reflood phases of a large-break loss-of-coolant accident (LOCA). REFLOD3B solves one-dimensional mass, momentum, and energy conservation equations. The code has been extensively used to analyze B ampersand W-designed plants and was recently modified to analyze recirculating steam generator PWRs. Modification included a new carryout rate fraction (CRF) correlation, CRFCKN; the addition of FLECHT and ANC correlations to determine core heat transfer; and a model to simulate the mass flow rate into the core bypass region. The code was assessed against FLECHT-SEASET gravity reflood test 33338. The CRFCKN correlation and the results of the FLECHT-SEASET test simulation are summarized here