What is the difference in PWR and BWR reactors?
Pressurized water reactor The most common of the reactor types, PWR reactors, originated as a submarine power plant. In PWRs, the water is kept under pressure so that it heats but does not boil. Coolant water from the reactor flows in a cooling circuit through the core of the reactor under very high pressure. A secondary circuit produces steam to drive the turbine. The water that is turned into steam travels in separate pipes and never mixes with the coolant water. PWRs use ordinary water as both coolant and moderator. A PWR has fuel assemblies of 200 to 300 rods each that are arranged vertically in the core. Large reactors have about 150 to 250 fuel assemblies. Boiling water reactor BWR reactors have many similarities to PWRs, except the water flows in only a single circuit under a lower pressure. The water that is heated by fission actually boils, and 12 to 15 percent of the water in the top part of the core is steam; therefore, the water has a lower moderating effect. A secondary co
