Experimental validation of control rod related perturbations of moderator regions in an SCWR-like fuel lattice

► Reaction rate distributions in SCWR-like lattices were calculated and measured. ► Experiments agree well with calculations using the probabilistic MCNPX. ► The deterministic code CASMO-4E generally agrees with MCNPX. ► Leakage gradients in the lattice require a special leakage treatment in CASMO-4E. ► Earlier doubts about CASMO's reliability for such lattices could be dispelled.