Thermal-Hydraulic Analysis of the Flow in the MICAS Experimental Facility Using CFD
Résumé
France has been developing Sodium Cooled Fast Reactors (SFRs) extensively in past five decades with lot of research being carried out in development phase. In the framework of Generation IV reactor program, extensive R&D is ongoing at CEA. Computational Fluid Dynamics (CFD) is a computational method that is being utilized in multi-scale calculations to correctly take into account complex 3D effects in safety transients. Recently investigated under these activities is thermal-hydraulic behavior in experimental and numerical setup, as they have been identified as important scientific subject in the development of SFRs. New experiments have been carried out, which provides the new insight into the design options and also provide a good amount of data for numerical study and codes validation. As sodium is a complex fluid to work with in experiments, large scale experimental tests were performed with water as the fluid. For this purpose, MICAS facility was developed, which represent the hot pool facility of the SFR in a 1/6th scaled down model. For experimental reasons, this facility is built in transparent polymer along with all internal features for accurate optical measurements of the flow field under various flow conditions.
The flow in the MICAS facility has been studied experimentally in details in two stages. First stage of test was conducted in isothermal conditions to study gas entrainment and hydraulic aspects of the flow, this has been already studied in detail in past. To study the thermal aspects, the second stage of tests were performed at steady-state thermal conditions. In this paper we present the computational analysis with focus on stabilized behavior thermal-hydraulic tests carried out with the TrioCFD code, which is the reference CFD code of Energy Systems Division of the CEA. The code has been developed and validated over the time from more than 25 years, to perform thermo-hydraulic analysis in nuclear reactors. Objective of the code is to able to study flow fields in different environments including capability to model complex geometrical structures with high resolution in time and space. It is also designed to utilize HPC (High Performance Computing) features to allow best management between mesh resolution and computational performance.
The main purpose of this study is to deal with the thermal distribution inside the hot pool facility and to study distribution of the flow and thermal behavior around the internal components. We will focus on validation of temperature values and temperature mixing during the phase when water at higher temperature is entered from core exit and at lower temperature is injected from the reflector and the internal storage areas; comparing with experimental data obtained by thermocouple trees at strategic locations.