In the Republic of Kazakhstan, within the framework of international initiatives on the non-proliferation of nuclear weapons, the IVG.1M research reactor is being converted to low enriched fuel. Due to the change in the fuel composition, it becomes necessary to assess the power density distribution in the fuel assemblies and in the core altogether. Close attention to this parameter is explained by the fact that the non-uniformity of the radial and axial power density fields determines the operating parameters of the reactor, its power, the core resource and the efficiency of fuel utilization. The purpose of this work is approbation of the activation gamma-spectrometry method for determining the power density distribution in the fuel of the IVG.1M research reactor after conversion. Additionally, for a preliminary assessment of the experimental outcomes, the paper presents the MCNP6 calculation results for the power distribution in fuel assemblies and the peaking factors. •The possibility of converting the IVG.1M reactor to low-enriched uranium was investigated.•A review of the main experimental methods for determining the power density fields is carried out.•The experimental method of determining the power density distribution in IVG.1M during the physical start-up is proposed.•The results of MCNP6 calculation of the radial and axial power distribution in the fuel of the IVG.1M are presented.•The comparative analysis of the axial power density distribution for HEU and LEU fuel is presented.