When it comes to efficiency and reliability, no other electricity source can match nuclear. Nuclear power plants can continuously generate large-scale, around-the-clock electricity for many months at a time, without interruption. Nuclear energy supplies about 10 percent of the world's electricity and approximately 20 percent of the energy in the United States. A total of 30 countries worldwide are operating nuclear reactors for electricity generation.
The fissioning of atoms in the chain reaction also releases a large amount of energy as heat. The generated heat is removed from the reactor by a circulating fluid, typically water. This heat can then be used to generate steam, which drives turbines for electricity production. In order to ensure the nuclear reaction takes place at the right speed, reactors have systems that accelerate, slow or shut down the nuclear reaction, and the heat it produces.
This is normally done with control rods, which typically are made out of neutron-absorbing materials such as silver and boron. Two examples of nuclear fissioning of uranium, the most commonly used fuel in nuclear reactors. Nuclear reactors come in many different shapes and sizes — some use water to cool their cores, whilst others use gas or liquid metal. Control rods can then be inserted into the reactor core to reduce the reaction rate or withdrawn to increase it.
The heat created by fission turns the water into steam, which spins a turbine to produce carbon-free electricity. All commercial nuclear reactors in the United States are light-water reactors. This means they use normal water as both a coolant and neutron moderator.
These reactors pump water into the reactor core under high pressure to prevent the water from boiling. The water in the core is heated by nuclear fission and then pumped into tubes inside a heat exchanger. Those tubes heat a separate water source to create steam. The steam then turns an electric generator to produce electricity.
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