Liquid-metal-cooled fast reactors are under development worldwide, 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 simulations. This paper describes 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 are presented for experiments and simulations, showing satisfactory comparisons. After that, initial work performed on solid blockages is described. It is shown that the first simulations of such blockages showed large discrepancies with the experimental results. As a result, a number of sensitivity analyses revealed the major contributors to these discrepancies, which led to the design of a porous blockage experiment and simulation campaign, which at the same time was more representative of the postulated reactor conditions. Finally, the results of the porous blockage campaign are shown.