The uranium -235 nuclear fuel in the nuclear reactor carries out chain nuclear reaction, resulting in high temperature. The high temperature "boils" the pure water in the closed cycle in the nuclear reactor into steam, which is accelerated into steam flow through the nozzle to drive the steam turbine to run. The speed of the steam turbine is reduced by the speed reducer to drive the propeller. The whole process of energy conversion is roughly as follows: nuclear energy → thermal energy → mechanical energy → kinetic energy.
Nuclear energy comes from the fission of uranium atoms in nuclear reactors. When uranium nuclear fission (called "chain reaction"), it will produce huge heat energy. The function of nuclear reactor is like a familiar boiler, but the water in the boiler is generally heated by fire, and the water in the nuclear reactor is "heated" by nuclear fuel, so the nuclear reactor used to be commonly known as "atomic boiler".
A nuclear power plant usually consists of a primary circuit and a secondary circuit, both of which are closed loop circuits.
The primary circuit consists of main coolant system and various auxiliary systems. The main coolant system includes nuclear reactor, main coolant pump, steam generator, voltage regulator and other equipment. After the high-temperature and high-pressure pure water in the primary loop is heated by the nuclear fuel, driven by the main coolant pump, the heat is transferred to the secondary loop water through the steam generator, making it become steam, and then the cooling water in the primary loop returns to the nuclear reactor again, continuing to take away the heat generated by the nuclear fuel and slowing down the neutron's participation in the chain nuclear reaction. So the water in the main circuit is called coolant and retarder. The heat released by nuclear fuel is controlled by control rods.
In the second loop, the steam heated by the first loop flows in the first half and the water cooled by the condenser flows in the second half. The intersection of the primary circuit and the secondary circuit is the steam generator. The water in the secondary loop is heated in the steam generator and becomes saturated steam to drive the turbine generator and provide power.