[en] Experimental methods and results of measuring the reaction rate space distribution in a homogeneous elementary uranium-water cell and in cells near the heterogeneities of a B₄C rod,air and water void types are described. Investigations were conducted in a subcritical uranium-water WWER bench by activation technique with subsequent irradiated uranium foil detector separation into parts using a coordinate electric-spark tool. The induced foil γ-activity was measured by γ-spectrometry method in two Li-drifted Ge semiconductor detectors. Analysis of the distribution determination errors as well as results of evaluating the fuel element temperature with regard to experimentally produced energy release irregularity over the fuel element radius are presented. The investigations have shown that the methods applied are sensitive to heterogeneities creating over 3.5% pertubations in ²³⁸U(n, γ)-reaction rate distribution and over 2.5% ones-in ²³⁵U(n, f)-reaction distribution. The maximum asymmetry in plutonium accumulation rate distribution in the fuel ent (up to 20-30%) is observed near the air and water voids. The maximum asymmetry in ²³⁵U fission rate distribution in the fuel element (up to 10%) is observed near the absorbing element