A steam generator in the context of nuclear power is a crucial component. Let’s delve into its purpose and characteristics:

1. Definition and Purpose:

   • A steam generator (also known as a nuclear steam raising plant or NSRP) is a heat exchanger used to convert feedwater into steam. It achieves this by utilizing heat produced in a nuclear reactor core.
   • These generators are employed in pressurized water reactors (PWRs) between the primary and secondary coolant loops.

2. How It Works:

   • In a typical PWR design:
     • The primary coolant is high-purity water, maintained under high pressure to prevent boiling.
     • This primary coolant circulates through the reactor core, absorbing heat from the fuel rods.
     • Next, it passes through the steam generator, where it transfers its heat (via conduction through metal) to lower-pressure water.
     • The lower-pressure water is allowed to boil, producing steam.
   • Unlike boiling water reactors (BWRs), which allow primary coolant to boil directly in the reactor core, PWRs use steam generators to separate the activated primary coolant water from the secondary coolant.
   • This separation allows humans to access a PWR’s turbines and other steam plant components during operation, reducing maintenance costs and improving uptime.

3. Steam Generator Characteristics:

   • In commercial power plants:
     • Each reactor typically has two to four steam generators.
     • Each steam generator can measure up to 70 feet (21 meters) in height and weigh as much as 800 tons.
     • A single steam generator can contain anywhere from 3,000 to 16,000 tubes, each approximately 0.75 inches (19 mm) in diameter.
   • The process involves:
     • Pumping coolant (treated water) through the nuclear reactor core.
     • Heat transfer between the reactor core and the circulating water.
     • Pumping the coolant through the primary tube side of the steam generator before returning to the reactor core (referred to as the primary loop).
     • Boiling water on the shell side of the steam generator (which is kept at lower pressure than the primary side) to produce steam.