Steam generator
In a nuclear power plant, steam generators are where the primary cooling loop transfers its thermal energy into the secondary cooling loop. Typically, this involves the high-pressure primary cooling loop going through a large number of winding and zig-zagging tubes that are surrounded by a bath containing the water in the secondary cooling loop. The heat then causes the water in the secondary cooling loop to evaporate and then make its way out of the steam generator.
Note that the two loops are constantly separated and therefore any contamination from the core remains in the primary cooling loop and does not get transferred to the secondary cooling loop.
It is extremely difficult to explain the steam generators without going into detail about the primary cooling loop, secondary cooling loop, tertiary cooling loop, containment, and so on.
