NPPs with VVER Reactors: System Efficiency of Variable Frequency Drives in the Main Circulation Pumps

Today the problem of maneuverability of nuclear power plants primarily related to those power systems where their market share is growing steadily, as in the center of the European part of the Russian Federation. One of the most effective technologies to fundamentally solve the problem of maneuverability of the water-cooled reactor is modernization of the main circulation pumps by installing variable frequency drives. These drives are used to increase the capacity of a nuclear power plant to a super-nominal, to control the frequency in the power system and to eliminate the system accidents. A technique for calculating the efficiency of variable frequency drives in the main circulation pumps of nuclear power plants with VVER reactors is proposed. The most important advantage achieved with the variable frequency drive of the main circulation pump is a possibility for an additional increase in the power up to 107 - 110% (at NPPs with VVER-1000 an increase up to 104% was achieved) without reducing the safety factor prior to the heat exchange crisis by increasing the coolant velocity. It is shown that an increase in the power, maneuverability, and acceleration capability of VVER nuclear power plants through installation of variable frequency drives in the main circulation pumps leads to an increase in the efficiency of NPPs.