Reduced RANS approach validation to model passive heat removal due to inter-wrapper flow

•Reduced-resolution CFD modelling of inter-wrapper flow in LMFRs is considered.•A resolution sensitivity study is performed for the influence on inter-wrapper flow.•Reduced-resolution scheme is selected with a maximum temperature difference of 16%.•Approach is validated using experimental data of unblocked/blocked bundle configurations.•Heat removal is predicted within 11%, with a substantial in computational cost.