Nuclear power

There is one powerful, reliable energy source that, when it is up and running, emits no greenhouse gases at all. Nuclear fission exploits the colossal amount of energy released by radioactive uranium when its atoms are split in a nuclear reactor. But radiation is extremely dangerous, and since a reactor can also be used to make nuclear weapons, nuclear power is the subject of fierce debate between those who support this form of energy generation and those who oppose it.

NUCLEAR FISSION

A single atom of uranium is unbelievably small, but it can be made to yield a huge amount of energy by splitting the nucleus at its heart into two smaller parts. This can be done by hitting it with a tiny particle called a neutron. As each atomic nucleus splits, it releases energy and more neutrons. These split more nuclei in a chain reaction. If this is not controlled, it can cause a nuclear explosion, but if it takes place in a carefully designed nuclear reactor, it just generates a lot of heat.

^-Split nucleus Energy /// Neutr

Neutron t /

Uranium nucleus split by neutron

Neutron

Reactor is enclosed in strong concrete building

Heat from the reactor is passed through boiler , to turn water to steam

Inside a nuclear power plant

Heat from the reactor is passed through boiler , to turn water to steam

Inside a nuclear power plant

Control rods adjust rate of nuclear reaction

Nuclear fuel rods generate heat in reactor

Fluid "coolant" carries heat away from reactor

NUCLEAR POWER PLANT

This nuclear power plant in England has two nuclear reactors. Each one contains rods of radioactive uranium that interact in a nuclear chain reaction. The reaction is regulated by "control rods"that are lowered between the radioactive fuel rods to absorb neutrons and stop the rods from interacting. The heat generated by the nuclear reaction heats a fluid that is pumped through a boiler to turn water into steam. This powers turbines linked to electricity generators.

Steam powers turbine linked to electrical generator

Generator produces electricity

Electricity carried away by power lines

Control rods adjust rate of nuclear reaction

Nuclear fuel rods generate heat in reactor

Fluid "coolant" carries heat away from reactor

Steam powers turbine linked to electrical generator

Generator produces electricity

Electricity carried away by power lines

Cooled steam forms water, which is pumped back to boiler

\Cooled water returns from cooling tower

Hot water flows I to cooling tower

Cooled steam forms water, which is pumped back to boiler

Steam cooled by cold water

\Cooled water returns from cooling tower

Hot water flows I to cooling tower

CARBON-FREE POWER

Nearly 80 percent of France's electricity is generated by nuclear energy. It powers France's famous high-speed train, or Train a Grande Vitesse (TGV), which covers long distances at up to 186 mph (300 km/h), rivaling aircraft for speed, but with zero carbon emissions. This gives France a relatively low "carbon footprint"in relation to its wealth and industrial productivity. However, although many other nations would like to follow France's example, nuclear power stations are very expensive and take a long time to build. Setting up an entire network can take ten years or more.

RADIOACTIVE WASTE

A nuclear power station uses a tiny quantity of nuclear fuel, but after it has been used, it remains highly radioactive for thousands of years. This is a serious problem, because the radiation is very dangerous to health. The waste must be handled by remote control and stored in special facilities while scientists try to find ways of making it safe. Here spent nuclear fuel is stored in a tank of water, which stops the radiation from escaping.

NUCLEAR WEAPONS

As well as generating power, nuclear reactors can be adapted to make nuclear bombs capable of destroying entire cities. If nuclear power becomes widely used, more countries may develop nuclear weapons, and possibly use them to threaten or even destroy their enemies. Radioactive material might also be stolen by terrorists, who could pack it around ordinary explosives to make"dirty bombs" that could spread dangerously radioactive dust.

Australian uranium mine

Hydrogen nucleus with two neutrons (tritium)

URANIUM MINING

Uranium—the radioactive metal used as nuclear fuel—is a rare metal that may be in short supply within a few decades. Mining it uses a lot of conventional energy that generates greenhouse gases, as does the construction of a nuclear power plant, so nuclear power is not entirely carbon-neutral. The mines also leave huge scars in the landscape.

Hydrogen nucleus with one neutron (deuterium)

NUCLEAR FUSION

If small atomic nuclei are smashed together, they can fuse together to make bigger nuclei. This is the opposite of nuclear fission, but it also produces huge amounts of energy. All the energy radiated by the Sun is generated by this nuclear fusion process. It does not involve radioactive fuel, and it does not create radioactive waste. But it does require a colossal input of energy to get it started, and controlling the process is very difficult. Experimental fusion reactors are now being tested at several laboratories around the world, but it will be a very long time before nuclear fusion is used to generate electricity.

Helium nucleus forms

NUCLEAR ACCIDENTS

In 1986 the Chernobyl reactor near Kiev in Ukraine overheated and blew up. Radioactive dust spread over a large area of the former USSR, and some was even carried around the world by the wind. Many people died of radiation poisoning, including a lot of the workers seen here trying to clear up the contamination. Many more will probably suffer cancers triggered by the radiation. The Chernobyl plant was a primitive, badly-run reactor, and modern nuclear power stations are far safer, yet many people worry that other nuclear power plants could explode. They also fear that nuclear plants could become terrorist targets.

Helium nucleus forms

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