Steam generator (nuclear power)

A steam generator (aka nuclear steam raising plant ('NSRP')) is a heat exchanger used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactor between the primary and secondary coolant loops.

In typical PWR designs, the primary coolant is high-purity water, kept under high pressure so it cannot boil. This primary coolant is pumped through the reactor core where it absorbs heat from the fuel rods. It then passes through the steam generator, where it transfers its heat (via conduction through metal) to lower-pressure water which is allowed to boil.