In 2022, the physical start-up stage of the IVG.1M research reactor was successfully completed, initiated by reducing the fuel enrichment of ²³⁵U. This phase included the loading of nuclear fuel into the reactor core and conducting experiments to determine the neutron-physical characteristics of the reactor. Prior to the physical start-up, preliminary calculations were performed using the computational code MCNP6 and a full-scale model of the IVG.1M reactor with low-enriched uranium fuel (LEU). During the start-up series, the reactivity worth curves of the reactor control and protection system’s operating and compensating elements were determined. Additionally, experiments were performed to measure the reactivity effects of technological channel draining and to obtain activation reaction rates in the central experimental channel using nickel and gold activation indicators. The results of determining the neutron-physical characteristics of the IVG.1M reactor have confirmed the operability of the reactor core with LEU fuel.

Prior to the commissioning of the IVG.1M reactor with low-enriched uranium fuel, experimental studies of reactor characteristics were carried out on physical and energy start-ups, which should confirm the results of preliminary computational studies and the operability of the reactor. This article is devoted to the study of the axial and radial energy release profile in the IVG.M reactor fuel assemblies using in-reactor dosimetry techniques. The experimental results are compared with the results of neutron-physical simulations. The obtained energy release irregularity coefficients can be used in further thermo-technical calculations.