Two-loop PWR RELAP5 to TRACE Model Conversion and Three Dimensional Vessel Model Development for Coolant Mixing Analysis - 14157

The analysis of some Design Basis Accidents requires multidimensional prediction of the thermal-hydraulic conditions in order to realistically simulate the accident. The main goal of the paper is to present the ongoing development of a model suitable for analyzing the coolant mixing phenomena in the reactor pressure vessel (RPV) of a Westinghouse (W) two-loop pressurized water reactor (PWR). The model is being developed using the best-estimate system code Trac-Relap Advanced Computational Engine (TRACE) and consists of a one dimensional model of a W two-loop PWR with a three-dimensional model of the RPV. The one dimensional TRACE input deck was converted from an existing RELAP5 input model using the Symbolic Nuclear Analysis Package (SNAP) conversion plug-in following the Jozef Stefan Institute (JSI) RELAP5 to TRACE conversion method. The three-dimensional TRACE model has been obtained by replacing the one-dimensional model of the RPV in the developed TRACE one dimensional input model with a three-dimensional model of the RPV. The three-dimensional model of the RPV has been developed using the TRACE specialized VESSEL component. Besides the presentation of the development of TRACE one dimensional and three dimensional models a preliminary steady-state calculation using the new TRACE one dimensional model is presented. For calculations, the latest TRACE V5.0 Patch 3 computer code was used. Finally, the TRACE one dimensional calculation results are compared with the RELAP5 calculation results. (authors)