Development, Verification and Validation of the Multi-Scale CATHARE-NEPTUNE_CFD Coupling

International audienceSystem Thermal Hydraulics codes have been extensively used and validated for operational and accidental transients in Pressurized Water Reactors. However, when complex 3D phenomena are expected to occur (e.g., during a Pressurized Thermal Shock), these codes can offer limited predictive capabilities due to the mostly 1D-lumped approach that they rely on.In the context of the French Neptune project, involving CEA, EDF, Framatome and IRSN, CEA and EDF develop the coupling between the System Thermal-Hydraulics code CATHARE and the Computational Multiphase Fluid Dynamics code NEPTUNE_CFD. The aim of this coupling is to develop a simulation tool that can be used for complete reactor calculations without loss of resolution while offering an affordable computational cost.In this paper, the coupling methodology implemented for both single and two-phase flow is presented. Then, the road map for the verification and validation of the coupling is explained and results are presented and discussed

Assessment of Neptune_CFD Applied to the Study of a Passive Safety Condenser: Modeling and First Validation Elements

International audienceInnovative systems are being considered for its application in Generation III and III+ concepts aiming safety enhancement and cost reduction by means of decreasing operator intervention dependency, maintenance and the redundancies of active systems. Several passive systems designs are studied such as a particular solution of a safety condenser where the residual heat of the core is removed by condensing the steam from the secondary circuit through a tube bundle immersed in a cooling pool. The application of numerical tools (such as the system code CATHARE) in the study of safety related transients with these systems is led by CEA, EDF and FRAMATOME in a conjointly effort. The main activity is code development and validation for the description of the condensation physics in the secondary and low pressure boiling in the cooling pool. On a numerical multiscale approach, CFD solutions are being assessed as well, foreseeing an eventual up-scaling to system codes to enrich the validation process. In this work, first steps towards the application of neptune_cfd for a safety condenser configuration are presented, including a contribution to its condensation model validation by confronting it against experimental data. The model implemented in the code for the condensation within tubes is described, and some selected experiences from the separate effects test bench COTURNE are chosen to be simulated. Results of the simulations are presented from which some conclusions are drawn, inaddition, perspectives for further validation are discussed