Nuclear Reactors
Types of Reactors | Parts of a Reactor | Links to Additional Information
Types of Nuclear Reactors
All of the reactors that produce mass quantities of electricity for the general public use fission. Believe it or not, most power plants work on the same principle; water is heated and changed to steam, the steam turns a turbine, and the spinning turbine generates the electricity. The only difference between different power plants is the fuel source used to heat the water!
In a boiling water reactor (BWR), water is piped directly into the reactor vessel where the nuclear fission is taking place. The energy released in the fission process boils the water, changing it to steam. This steam is then piped out of the reaction vessel and containment structure into the turbine. The pressure of the steam turns the turbine, which in turn powers the generators.
In a pressurized water reactor (PWR), water is piped into the containment vessel, but is not in direct contact with the material undergoing nuclear fission. The energy released in the fission process superheats water in the reactor vessel, which in turn heats water in a separate, sealed off container. This water is then changed to steam. This steam is then piped out of the reaction vessel and containment structure into the turbine. The pressure of the steam turns the turbine, which in turn powers the generators.
Parts of a Reactor
- Fuel Rods - Contains thousands of pellets of uranium fuel, usually in the form of uranium dioxide (UO2) or uranium hexafluoride (UF6). One pellet (roughly the size of a small piece of chalk) can produce an amount of energy comparable to 1 ton of coal.
- Control Rods - When fission occurs, the neutrons that are released cause other fission reactions. If left unchecked, a chain-reaction will occur with horrific consequences. To limit the number of neutrons that are allowed to split other atoms, control rods made of boron or cadmium are used to absorb these neutrons. The control rods are raised and lowered into the reaction vessel, depending on how much electricity needs to be generated by the reactor.
- Moderator - The neutrons that are released during fission are moving at extremely high rates of speed. In fact, they are moving too fast to effectively continue the fission process. A moderator is used to slow down these neutrons. Ordinary water, heavy water (made with deuterium, aka Hydrogen-2), or graphite are commonly used moderator materials.
- Generator - This includes the system of pipes that hold the water that is turned to steam. The steam then turns the turbines, as described and illustrated above.
- Cooling System - After the steam turns the turbines, it condenses, and is recycled back through the reactor. In order to condense this steam, however, the heat must be removed. One method is by piping water in from a nearby body of water (i.e. - lake, river, etc.). This water absorbs the heat and turns to steam (which is then released through the familiar large steam stacks), or is returned to the original body of water.
Links to Additional Information
top
