Numerical investigation of flow diffuser optimization for a PWR reactor with Code-Saturne - Analysis on EPR type reactor

In order to provide scientific basis for new reactor design in terms of optimal Flow Diffuser, a study was launched on the analysis and investigation on flow distribution of existing flow diffuser design of five different reactors including EPR, VVER, Konvoi, APR+ and Westinghouse. The strategy is to change each time only the flow diffuser within the 1/5 scale BORA mock-up¹. The authors consider that the optimal design needs to reach a homogeneous inlet core flow rate, which is defined as figures of merit. This study combines PIRT (Phenomena Identification and Ranking Table) methodology and Computational Fluid Dynamics (CFD) calculations to identify the optimal flow diffuser design. This paper introduces main physical phenomena analysis with PIRT methodology to list the most important phenomena and parameters from cold legs to lower core plate which have a high level of influence on the flow distribution at reactor core inlet for EPR reactor type. CFD calculations are performed under the injection condition of 0.1 m³/s per cold leg at 1/5 scale BORA mock-up for EPR flow diffuser configuration. EDF in-house open-source codes are applied to perform CFD calculations including Salomé² for pre-processing and post-processing and Code-Saturne³ for solver.