[en] Method of topological description of former nuclear tests is demonstrated using Semipalatinsk nuclear test site as an example. Information about the field extracted from the topology of 2D cross-section of 3D surfaces constructed on experimental data. Complexity of isolines system for each cross section is estimated by algebraic sum of contours bounded the areas where the field is higher than the given level. The method gives an opportunity to do morphological analysis of radionuclide fields using archive data and can be used for ecological diagnosis of different contamination