We have analyzed the measures to improve the theory for controlling the technical state of equipment in nuclear power plants. These measures should be considered as a comprehensive sectoral solution to the problem of ensuring reliable and safe operation of existing and newly constructed nuclear power plant units. The tasks discussed are of great importance for transition to a system for repairing NPP power equipment based on technical condition, as well as management of its operation, depending on reliability indicators throughout the life cycle of the NPP. The scientific and practical significance of solving these problems also consists in creating models, algorithms and computer programs aimed at ensuring reliable, safe and efficient operation of NPP power equipment. This is achieved by improving the system of maintenance and repair and operating modes, taking into account the actual technical state of the power equipment.