A steam generator is a heat exchange device that produces the steam required for a steam turbine. In a nuclear reactor, the energy produced by nuclear fission is carried away by the coolant, and the heat is transferred to the feedwater of the secondary circuit through the steam generator, producing steam with a certain pressure, temperature, and dryness. This steam then enters the steam turbine to do work, converting thermal energy into electrical or mechanical energy. As shown in Fig. 1.1 , in this energy conversion process, the steam generator functions as both a primary and secondary circuit device, so it is called the hub of the primary and secondary circuits.