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 thin walled U-Bend 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 turn to steam and then make its way out of the steam generator(s) and on to the turbine-generators.

Note that the two loops are constantly separated and therefore any radioactive contamination from the reactor core remains in the primary cooling loop and does not get transferred to the secondary cooling loop.

A common way of inspecting steam generator tubing is by the non-destructive testing method of eddy current.

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.

Steam generators are found only in pressurized water reactor (PWR) type nuclear power plants.