The thermal hydraulics in a rod bundle representative of the start-up core of the ALLEGRO Gas cooled Fast Reactor—Experimental and numerical approaches

Abstract

The ALLEGRO project, led by the CEA in the European framework, is devoted to the conception and the building of the first Gas cooled Fast Reactor (GFR) demonstrator. In order to fulfil this ambitious challenge, the ESTHAIR program has the objective to validate some thermal-hydraulic aspects, mainly the correlations on the pressure loss and on the heat exchange coefficients within the core sub-assemblies, between the fuel pin and the helium coolant. This program is supported by: • an experimental air test section, which is designed to produce data for pressure drop and heat transfer coefficients for the various ALLEGRO fuel assembly concepts; • a numerical simulation program based on a simplified modelling of the ESTHAIR sub-assembly. The experimental pressure loss and heat transfer coefficients are compared to the existing correlations and to the calculated results. The study concludes in the good reproducibility of the experimental results by the numerical simulation, which will allow the selection of the most appropriate correlations.