GETR multi-channel core model for simulating internal natural circulation

A computer model (CORFLO) of a four-parallel-region core to analyze internal natural circulations and low flow events is described. The model is a quasi-steady state, includes top and bottom common plenums, and calculates the region flows and the fluid temperature distribution in the core. Detailed analyses of accident events (major pipe and nozzle breaks) in the General Electric Test Reactor are presented. Simulation of flow reversal cases, such as the loss of electrical power with either one or two emergency cooling valves open, is discussed. A description of a single-channel model (HOTCHAN) is presented. The model is used to determine peak temperatures and to analyze the flow in the channel with the highest power. Pump shaft seizure and pump rotor breakage events have been also simulated by the program. Because of its limitation in analyzing fast transients, the model greatly overpredicts flow temperature (or enthalpy) excursions