A Study of the Possibility to Uprate an NPP with a VVER-1200 Reactor through Feedwater Heating in an Economizer with Installing an Additional Turbine

A search of efficient ways for uprating the existing NPPs deserves close attention owing to significant saving of expenditures for implementing them in comparison with construction of new NPPs. In this connection, a new method for uprating an NPP with water-cooled reactors is proposed and discussed, which involves heating of feedwater in an economizer prior to supplying it to the steam generators by using the reactor coolant from the steam generator’s outlet. This results in an increased main steam output from the steam generator without changing its thermal power capacity, and a decrease in the average coolant temperature in the reactor core without changing it at the reactor outlet helps increase the core reactivity. With excess steam supplied to an additional steam turbine unit, it becomes possible to decrease the total costs for a power unit’s modernization and enhance the NPP safety through providing backup power supply for power plant auxiliaries in case of an emergency involving station blackout. A process cycle circuit of an NPP with a VVER-1200 reactor involving feedwater heating in an economizer upstream of the steam generator is developed and substantiated. The economizer main characteristics required for feedwater heating to 245 and 265°C are determined. The effect from installing the economizer on the reactor coolant pump operation and on the reactor coolant circuit as a whole is determined. It is shown that the power output of the NPP unit with a VVER-1200 reactor and with an additional turbine increases by 37.17 and 95.88 MW, respectively, with feedwater heated to 245 and 265°С.