On the efficiency of variable frequency drives of the main circulating pumps of nuclear power plants with water-cooled (VVER) and fast neutron reactors (BN)

Abstract

In case of communication losses with the power system and violations of external power supply, difficulties arise with the removal of residual heat generation of stopped reactor plants of NPP with water-water power reactors (VVER). The structural share of these power units grows. That is why they should be responsible for successful emergency frequency control, preventing the collapse of the power system. This is especially important when the frequency decreases with a prolonged growing generation deficit. In this article, we consider the possibilities of increasing the acceleration of NPP with VVER due to the implementation of fast load surges, as well as through prolonged operation with a power higher than the nominal. In both cases, an increase in the rotational speed of the main circulation pumps by the regulation of their drive motors by frequency converters is proposed for NPPs with VVER to increase the values of the crisis heat flow and increase the permissible temperature at the outlet from the core for the same safety reserves. The article briefly analyzes the experience of the introduction and operation of the variable frequency drive of the main circulation pumps at nuclear power plants with fast neutron reactors BN-600 and BN-800. It is noted that due to the smooth regulation of the flow of sodium coolant by the pumps in the main circuits, the problem of the maneuverability of nuclear power plants with BN reactors was largely solved. These decisions, taken already at the design stage of the third and fourth power units of the Beloyarsk NPP and proven positively in operation, were implemented in the project of the 5 th power unit with a fast neutron reactor BN of 1200 MW.