The information on this page was prepared by:
| Benjie DeVera | devera@usc.edu | Undeclared Engineering |
Pressurized Water Reactor
The pressurized water reactor (PWR) is one of the most common reactor type used in the world. It gives about 64% of the total power of today’s operating nuclear power plants. Out of 104 licensed operating nuclear plants in the United States, 69 of them are PWRs. PWR functions similarly with a BWR but is distinguished by the the components inside the containment structure: the pressurizer and the number of cooling loops (sometimes called circuits) that connects to it.
Inside the reactor vessel or the core is where heat is created. To remain a liquid throughout the process, the pressurizer keeps the pressure high to balance it with the temperature in the primary loop. Pressurized water goes into the primary coolant loop, which continues to carry the heat into the steam generator. The steam generator is connected to a secondary loop, heated by the primary loop that provides steam for the turbines. The maximum turbine temperature is limited to that heat in the reactor core. As the turbine rotates, the generator connected to it will produce the electric energy. The steam falls to the condenser where it condenses and becomes liquid again. It goes into the feedwater in the bottom of the reactor (not labeled in the diagram) that is connected to the primary loop that goes into the reactor core.
The primary and secondary loops serve for safer purposes. When water inside the core is overheated, pressure sensors inside the pressurizer detects it from the secondary loop and opens spray valves at the top to condense back some of the steam and ultimately lowers its pressure. Similarly when the temperature declines, heaters in the bottom of the primary loop turns on that increases the reactor core’s temperature and pressure. Another advantage the PWRs have regarding the two loops is that it allows isolation to the environment. For example, the water in the primary loop affects the water in the secondary loop independently because the reactor vessel separates it. Control rods control the heating process inside the vessels’ temperature.