Events that lead to damage to the blades can occur during the operation of turbine equipment at nuclear power plants. In some cases, it may not be possible to quickly replace damaged parts. The purpose of this study is to investigate the possibility of operating the K-1000-60/3000 turbine with dismantled nozzle and working blades of the 5th stage. A mathematical model of the flowing part of a high-pressure cylinder based on the object-oriented approach is developed. The main thermodynamic and kinematic parameters of the flow are investigated. A significant change in the steam parameters in the extraction III, which feeds the main deaerator of the unit, has been established. The steam pressure in this extraction decreases by 37% and is insufficient to ensure the nominal deaeration of the feeding water. At the same time, the total power of the cylinder without the 5th stage is reduced by 3%. The thermal and stress-strain state of a high-pressure rotor in the project version and without a damaged stage was investigated. A decrease in the overall stress level and migration of the areas of maximum stresses were observed. The low-cycle fatigue of the rotor was investigated at typical operating conditions. It was found that the individual rotor life without the 5th stage increases by 5.6%.