Major Components
Reactor
A reactor vessel with 8-inch thick steel walls houses the fuel rods. Within the reactor vessel, nuclear fission--the process of splitting atoms of uranium to release energy--occurs. This energy heats pressurized water to more than 600 degrees Fahrenheit without boiling. During the reactor operation, water flows rapidly through the reactor vessel.
This water serves two key purposes. It acts first as a coolant to transfer heat from the fuel rods to the steam generator. Second, it slows down neutrons and increases the probability of fission. Just as in a baseball game -- where a batter is more likely to hit a slow ball than a fast ball -- a slow-moving neutron is more likely to hit a uranium atom and split it.
The "moderating" effect of the water adds another safety feature. Any loss of water would slow down the chain reaction.
Fuel Rod Assemblies
Fuel Rod Assemblies are comprised of fuel rod bundles and control rods.
The fuel is made up of small uranium pellets, about as big as the end of a finger. These pellets are dense, ceramic materials placed end-to-end inside long metal tubes called fuel rods. The fuel rods are then grouped together in bundles, and arranged so that control rods can be placed between them.
Control rods are used to slow or stop the fission process. They are made with a substance that absorbs neutrons. Moving them in or out of the reactor controls the amount of heat being produced.
Steam Generation System
After leaving the reactor, the hot pressurized water passes through pipes submerged in cooler water in a steam generator. Within this generator, the pressurized water gives up its heat to a second, separate supply of water which boils -- making steam for the turbine.
After giving up its heat, the pressurized water recycles back to the reactor vessel to be reheated again.
The reactor vessel and steam generator are enclosed in a massive, reinforced, air-tight concrete structure, called the containment, with concrete and steel walls more than four feet thick.
Turbine / Generator
As in a coal, oil or natural gas power plant, this steam passes through a steam line and into a turbine generator. Steam striking the propeller-like blades causes them to rotate just as the wind blows the blades of a windmill.
This rotation of the turbine blades spins the shaft of the generator. Inside, coils of wire, and magnetic fields interact to produce electricity.
A third, separate cool water system from the ocean interacts with the steam to condense it back into water for recycling to the steam generator.
