A dynamic thermal-hydraulic simulation of the Oconee 1 main/emergency condensate/feedwater trains

Original development and validation of a RELAPB-compatible computer model that simulates the dynamic thermal-hydraulic behavior of the Oconee 1 nuclear station main and emergency condensate feedwater trains is described. The stand-alone model, which was generated for incorporation in the Idaho National Engineering Laboratory and Los Alamos National Laboratory pressurized thermal shock Oconee 1 total plant models, is introduced through a generic discussion of the nominal operation of the steam and power conversion system. This synopsis establishes a foundation for the detailed examination of the thermal-hydraulic characteristics of the main and emergency condensate feedwater train components under atypical operating conditions such as those found during the three major classes of pressurized thermal shock transients: loss of main steam, steam generator overfeed, and recoverable loss of primary coolant.

This RELAP5 model combines the operating information, system geometry, and steady-state thermodynamic state points of the Oconee 1 main and emergency condensate feedwater trains into a collection of hydrodynamic volumes, hydrodynamic junctions, and heat structures. The details of this model are defined explicitly by including both the actual RELAP5 input stream and the initial processing of this input stream.

Dynamic responses to a hypothetical main steamline break of several Oconee 1 main and emergency condensate feedwater train parameters were generated using the developed model. The results of this transient and others performed using both the Idaho National Engineering Laboratory and Los Alamos National Laboratory Oconee 1 total plant models verify the ability of this state-of-the-art thermal-hydraulic model to calculate representative steam generator secondary-side inlet dynamic fluid conditions for pressurized thermal shock scenarios.