We have used the representativity theory in order to extend the validation of DARWIN. It concerns the upper and lower axial blankets of the fissile assemblies of SFR’s. These are not covered by the DOUBLON experiment measurements. We compute representativity factors of the final 239Pu/238U ratio in various fertile zones. The measurements in the radial zone reduce the uncertainty of the axial blankets calculations. The uncertainty reduction is a factor 5, since the experimental uncertainty is low. The uncertainty reduction decreases if the error becomes important. The 240Pu/238U ratio is studied with a similar method.