Preliminary Thesis on the First and Second Part of the ALLEGRO CFD Benchmark Exercise

TL;DR

This paper presents initial findings and 3D CFD modeling of flow in a nuclear fuel rod bundle test section, aiming to improve simulation accuracy for nuclear reactor coolant behavior.

Contribution

It introduces a new CFD modeling approach for the ALLEGRO benchmark and provides detailed geometry and flow analysis for nuclear fuel assembly simulations.

Findings

CFD models help understand inlet flow conditions.

Flow straightener effectively conditions velocity fields.

3D modeling supports accurate simulation of nuclear fuel bundles.

Abstract

At BME (Budapest University of Technology and Economics) NTI (Institute of Nuclear Technics), a 7 pin rod bundle test section has been built in order to investigate the hydraulic behavior of the coolant in such design and to develop CFD models that could properly simulate the flow conditions in the ALLEGRO core. PIROUETTE (PIv ROd bUndlE Test faciliTy at bmE) is a test facility, which was designed to investigate the emerging flow conditions in various nuclear fuel assembly rod bundles. The measurement method is based on Particle Image Velocimetry (PIV) with Matching of Index of Refractory (MIR) method. In the test loop, it was necessary to install a flow straightener that was able to condition the velocity field before the rod bundle. The results of CFD simulations could be used to improve the understanding of the inlet conditions in the rod bundle test section.The second part of the benchmark deals with the 3D CFD modeling of the velocity field within the 7 pin rod bundle placed in the test section. The geometry of the test section will be given to the participants in an easy-to-use 3D format (.obj, .stp or .stl).