[en] As a part of the Fast Reactor Cycle Technology Development Project (FaCT Project), the effect of local feedback reactivities on power distributions during control rod withdrawal in a large sodium-cooled fast reactor was studied. In UTOP transient analysis based on the point reactor kinetics model, power distribution skewing due to control rod withdrawal is usually given by the steady-state core neutronics calculation results obtained prior to transient analysis. However, the power distribution skewing during transient could be different from that in the steady-state core condition due to the effect of local feedback reactivities, allowing some time delay induced by the temperature rise in the fuel assemblies adjacent to the withdrawn control rod. In particular, UTOP allows the reactor system several minutes to activate the SASS and gives sufficient time to develop local feedback reactivities. The present study includes a configuration of the core calculation model which takes into account the transient temperature rise in the fuel assemblies adjacent to the withdrawn control rod, and a calculation of the power distribution skewing of the core. The calculated results are compared with those using the steady-state core conditions. It is shown that core radial power distribution skewing is significantly mitigated by local feedback reactivities (fuel Doppler and fuel axial expansion) due to temperature rise in the fuel assemblies adjacent to the withdrawn control rod, which corresponds to the transient over power core conditions. The calculated maximum power density ratio is 1.30, smaller than 1.39 calculated under the steady-state core condition. (author)