Nuclear power plants produce electricity in much the same way as fossil-fuel generating plants. The basic process is the creation of steam to spin a turbine and drive an electric generator. The generating equipment is similar at all thermal power plants; the major difference is nuclear power's method of creating steam.
At nuclear plants, a nuclear reactor takes the place of a combustion boiler. The heat that produces the steam comes from the energy released during fissioning (splitting the atoms) of uranium fuel, rather than from burning a fossil fuel such as coal.
A controlled nuclear chain reaction takes place in the reactor as neutrons from one splitting atom strike other atoms, causing them to split and release heat energy. This reaction can be started, controlled and stopped by movable control rods that absorb the released neutrons.
The chain reaction begins as technicians withdraw the control rods from the reactor core; the neutrons release and fissioning begins to create heat. A control rod, inserted into the reactor core, acts as a blotter to absorb free neutrons and slow the fission process. The chain reaction stops and electricity production halts when workers insert all rods.