09 February 2011

Difference between pressurized water reactor and boiling water reactor

Pressurized water reactor
Boiling water reactor
The coolant is not permitted to boil in the core of the PWR.
The coolant is permitted to boil in the core of the BWR.
In a PWR the heat from the reactor is passed through a boiler to generate steam which goes to the turbine that drives the electrical generator. This is called an indirect cycle.
In a BWR the steam generated in the reactor core is taken straight to the turbine, without the use of an intermediate boiler. This is known a direct cycle.
The pressure in a pressurized water reactor varies from the primary to the secondary system. In the primary system, the pressure is maintained at about 2250 pounds per square inch to prevent steam from forming. The pressure is then lowered for steam, at 600 pounds per square inch, to form. The pressure is controlled by a pressurizer.
The boiling water reactor operates at constant pressure. The primary system operates at pressure about one-half that of a pressurized water reactor's primary system while producing steam of equal quality.