3. DESCRIPTION OF PROGRAM OR FUNCTION
COBRA-3C/RERTR is a modification of the COBRA-3C/MIT, thermal-hydraulic nuclear reactor subchannel analysis program for research and test reactors (RERTRs), which are operated at low pressure and low temperatures and may use plate-type fuel elements and heavy water as coolant. COBRA-3C/RERTR incorporates critical heat flux correlations suitable for low-pressure systems, flow instability correlations, two-phase heat transfer coefficients suitable for research and test reactors, thermodynamic properties of heavy water, the capability of calculating the thickness of oxide film on an aluminum fuel plate, and the void fraction model based on the Bowring bubble detachment criterion. A plotting capability is included to display transient results.
The program calculates the steady-state power margins for reactors using either rod- or plate-type fuel elements. For the rod-type fuel the power margin is limited by surface clad temperature based on subcooled nucleate boiling heat transfer. For the plate-type fuel the power margin is limited by the flow instability rate (FIR), which is defined as the ratio of the reactor power at which the flow instability will occur to the operating power. The program is also capable of calculating the limiting thermal-hydraulic parameters in a RERTR for both loss-of-flow and power-ramp transients. COBRA-3C/RERTR uses the proprietary ISSCO DISSPLA graphics software which is not included.