[en] Fission density distribution in the reactor core was studied during the operation of the IBR-2 reactor at zero power in the beginning of 1978. The intensity of residual γ activity was estimated by measuring the height and turning angle of fuel element clusters with respect to scitillation detector. Fuel element clusters extracted from the reactor core were installed so that any point on their surface could be oriented from a distance to face a tungsten collimator. It is shown that volume inhomogeneity coefficient obtained experimentally is in agreement with the theoretical one, i.e. it is equal to 1.56. The most energy tense area of the reactor core was outlined. The distribution measured is in agreement within the accuracy limit with that calculated by the Monte-Carlo method. Some periphery areas of fuel element clusters were found to have higher fission intensity possibly due to fission on epithermal neutrons scattered by a moving reflector