A comprehensive analysis of emergency power supply systems at NPPs with WWER-1000 type reactors based on additional steam turbines in the context of Balakovo NPP

Abstract

An emergency power supply system for NPPs based on additional steam-turbine units is pro-posed. Under complete blackout of a station, it is possible to cool-down the VVER-1000 type reactors using the energy of residual heat release of the reactors. While maintaining the temperature of the primary coolant at the constant level, it will be possible to use additional steam-turbine units for electricity generation. The system is considered in the context of two units of Balakovo nuclear power plant. The calculations showed that a single low-power steam-turbine unit by utilizing the energy of residual heat release from one reactor is capable to provide electricity for two VVER-1000 power units, including the cases when the first circuit in one of the units is depressurized. It is shown that in line with IAEA requirements, the proposed system makes it possible to ensure the safety of nuclear power plants in case of complete blackout. At the same time, under standard operating conditions of NPP, additional steam-turbine units participate in generation of electricity. On the basis of statistical and probability analysis, we determined the annual reduction in the risk of the core damage. The technical and economic efficiency of the proposed redundancy system was assessed, taking into account the annual reduction in the risk of the core damage and cases with no damage. It is shown that the system is cost effective due to electricity generation under the regular NPP operation mode, even without any account for lowering the risks of the core damage.