Experiments and CFD for wire-wrapped fuel assembly blockages

Liquid metal cooled fast reactors are under development world-wide with the aim to contribute to an increased sustainable nuclear future. These reactors often employ wire-wrapped fuel assemblies in the core. For the safety assessment of such reactors, a reasonable prediction of the flow and temperature field in the fuel assemblies is required, both for operational as well as for accidental conditions. This is usually achieved using a combination of experimental work and various types of numerical simulation. This paper will describe the collaborative work performed by European partners with respect to the effect of blockages in wire-wrapped fuel assemblies. To begin with, results for an unblocked situation will be presented for experiments and simulations, showing satisfactory comparison. After that, initial work performed on solid blockages will be described. It will be shown that first simulations of such blockages showed large discrepancies with experimental results. As a result, a number of sensitivity analyses revealed the major contributors to these discrepancies, which has led to the design of a porous blockage experiment and simulation campaign, which at the same time is more representative of the postulated reactor conditions. Finally, the first results of the ongoing porous blockage campaign will be shown.