rector model for Ringhals-1 simulator RELAP5-HD SimExec design

It was decided to upgrade the recent reactor model of Ringhals-1 (R1) simulator by employing the modern simulation technologies based on the RELAP5-HD and Simulate-3R (S3R) codes. RELAP5-HD, which is the SimExec (GSE Simulator Executive) version of Relap5-3D, is used for the thermal hydraulics calculations while Simulate-3R is used for the 3D core neutron kinetics simulation. The RELAP5-HD model was designed using non-equilibrium, non-homogeneous and two-phase flow options. The semi-implicit solution scheme was used to solve the set of equations. The thermal hydraulic model of the core was designed by subdividing the reactor core into the six sectors. These six sectors comprise 13 thermal hydraulic channels, which are derived from 648 actual fuel assemblies. The S3R code uses a model which includes all 648 fuel assemblies. Both thermal hydraulic and neutronic models of the active core contain 12 axial planes. In addition, the S3R model has upper and lower axial reflectors along with radial reflectors. Downcomers, inlets and outlets to the external loops and lower plenum were constructed using 3D components in order to account for asymmetry phenomenon, which may appear during the trip of pumps or malfunctions in the feedwater system. The latest simulation technology, allowing usage of several SimExec's, was used for this project. Two SimExec's were used for the complete modelling of the reactor system. SimExec-1 was acting as a master and running all modules included in the Balance of Plant (BOP) simulator part. SimExec-2, containing RELAP5-HD and S3R, was used as servers (slaves) performing actual calculations requested by the BOP. In the SimExec-2 environment, RELAP5-HD performs thermal hydraulic calculations and sends results to the S3R through SimExec-1. S3R runs 3D neutron kinetics calculations based on mapping and interpretation of feedbacks from the RELAP5-HD. After S3R's calculations are completed, power distribution in the 3D core is obtained. A mapping procedure, programmed in S3R, lumps calculated power and sends to the RELAP5-HD for next calculation step. RELAP5-HD was compiled as an executable and linked using standard linking procedure in the SimExec environment. The model itself is designed by using standardized data input file, which describes the thermal hydraulic model. A standard version of SNAP package was used as a tool for graphical input deck design. The multi-server SimExec technology allows accessing all possible RELAP5-HD and S3R variables by employing different visualization tools. Using these tools it is possible to visualize the simulation models and study complex phenomenon in more intuitive way. These visualization tools are as plug-ins into the simulation models and can be used for debugging of the models and more comprehensive training of operators and design engineers. (authors)