PLANTWIDE RESERVATION OF OWN NEEDS OF A NPP BASED ON THE HEAT ACCUMULATION SYSTEM, INCLUDING A LOW-POWER STEAM TURBINE
Modern safety systems have a number of disadvantages, such as high cost and single-purpose use, leading to the cost of maintenance. Previously, an alternative option for cooling down VVER-type reactors with complete de-energization by power supplying of own needs consumers through the beneficial use of residual heat energy from the core to generate steam, which serves as working heat for an additional low-power multi-functional steam turbine, was developed and justified. As calculations based on the experimental data of the Balakovo NPP showed, the energy of residual heat generation of one VVER-1000 reactor is enough to cool two VVER-1000 reactors in an emergency situation, accompanied by a complete blackout when the primary circuit is depressurized on one of them for 72 hours. In the normal mode, the effective operation of an additional steam turbine can be ensured by combining the nuclear power plant with a heat accumulation system. An energy complex based on combining nuclear power plants with a phase transition accumulator and an additional multifunctional steam turbine installation has been developed. The investigation of the developed energy complex for the possibility of accumulating excess energy of the reactors residual heat and, as it decreases, effectively using the accumulated excess purposely to increase the time of autonomous power supply of the station's own needs in emergency situations accompanied by complete blackout, was carried out. The effect can be achieved due to the possibility of increasing the temperature of the feed water at the entrance to the steam generators of nuclear power plants, that in conditions of decreasing residual heat energy, will be possible to maintain at the required level the flow rate of generated fresh steam into a multifunctional steam turbine. The worst case, when the accumulator is in a discharged state, was investigated for two emergency situations with a complete blackout of four power units: without depressurization and with depressurization of the first reactor circuit of one of them.