Nuclear Power

How is nuclear power produced

The nuclear reactor lies at the heart of nuclear power.  It provides the conditions necessary for maintaining a controlled nuclear chain reaction, which releases heat to raise steam for generating electricity.  Where electricity is created from nuclear plants the process relies on nuclear fission. 

In this process, the nucleus of a heavy element, such as uranium, splits when bombarded by a free neutron in a nuclear reactor.  The fission process for uranium atoms yields two smaller atoms, one to three free neutrons, plus an amount of energy. Because more free neutrons are released from a uranium fission event than are required to initiate the event, the reaction can become self-sustaining, a chain reaction, under controlled conditions, thus producing a tremendous amount of energy.
 
In the vast majority of the world's nuclear power plants, heat energy generated by burning uranium fuel is collected in ordinary water and is carried away from the reactor's core either as steam in boiling water reactors or as superheated water in pressurised-water reactors. In a pressurised-water reactor, the superheated water in the primary cooling loop is used to transfer heat energy to a secondary loop for the creation of steam.

In either a boiling-water or pressurised-water installation, steam under high pressure is the medium used to transfer the nuclear reactor's heat energy to a turbine that mechanically turns a dynamo (or electric generator). Boiling-water and pressurised-water reactors are called light-water reactors, because they utilise ordinary water to transfer the heat energy from reactor to turbine in the electricity generation process. In other reactor designs, the heat energy is transferred by pressurised heavy water, gas, or another cooling substance.

Because the water used to remove heat from the core in a light-water reactor absorbs some of the free neutrons normally generated during operation of the reactor, the concentration of the naturally fissionable 235U isotope in uranium used to fuel light-water reactors must be increased above the level of natural uranium to assist in sustaining the nuclear chain reaction in the reactor core: the remainder of the uranium in the fuel is 238U. Increasing the concentration of 235U in nuclear fuel uranium above the level that occurs in natural uranium is accomplished through the process of enrichment.