  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).
