Nuclear Power Plants Use the Amazing Power of the Atom to Generate Electricity with a Very

Intoduction

Nuclear power plants use the amazing power of the atom to generate electricity with a very low fuel cost and much less pollution than fossil fuel plants. However, the planning, building, and operating of a nuclear power plant is a long, costly, and very complex process.

When the idea for nuclear power plants first came out, the Atomic Energy Commision (AEC) claimed that it would be a cheap way of generating electricity. Compared with fossil fuel power plants, nuclear power plants use very little fuel, so the cost is small, but it is made up for in other areas. The AEC was wrong. In fact, today, nuclear power plants cost just as much to build and run as coal plants do.

Nuclear power is generated using Uranium, which is a metal mined in various parts of the world.

The first large-scale nuclear power station opened at Calder Hall in Cumbria, England, in 1956.

Some military ships and submarines have nuclear power plants for engines.

Nuclear power produces around 11% of the world's energy needs, and produces huge amounts of energy from small amounts of fuel, without the pollution that you'd get from burning fossil fuels.

Constructing

After an order is received to start working on a nuclear power plant, the long multi-year process begins. The most important part of a plant is the nuclear reactor. That is where the nuclear reactions take place. During these reactions radiation is released. To make sure that none of this radiation is released into the environment, the building that houses the reactor must be made to hold it in. The reactor is housed in a dome-shaped building made with extremely thick walls of concrete and steel. The building must be strong enough to stand even if a jet plane crashed into it!!

The engine house is the building where the control and computer rooms are located. In the control room, engineers constantly keep watch over the entire power plant. If something were to go wrong, an alarm would sound and by the simple push of a button the problem would be automatically fixed. In the computer room, many computers are constantly recording information on every little thing that happens in the power plant. The construction of the buildings, the reactor, and the complex electrical network needed to run the power plant could take years. Then electricity can be generated.

The Generating Process

Billions and trillions of atoms, tiny little particles, make up all matter. Inside of an atom, there is a core, or nucleus made up of protons and neutrons. When the nucleus of an atom is split, nuclear fission occurs. That is what happens in the core of a nuclear reactor, and is the start of the process of generating electricity in a nuclear power plant.

Uranium, the most commom fuel, is placed in rods in the reactor's core. Free neutrons are released into the core. When a neutron hits the nucleus of a uranium atom, fission occurs, tremendous amouts of heat are released. When the nucleus was split 2 or 3 neutrons were set free. Those, in turn, split the nuclei of other atoms, setting more neutrons free. A chain reaction takes place in the core creating large amounts of heat. A coolant circulates around the rods of uranium in the core. The most used coolant is water, but newer plants use liquid metal instead.

As you might have guessed, the coolant is used to keep the reactor from getting too hot. It is also needed in the generation process. The coolant absorbs the heat produced by fission. It travels through tubes until it reaches the steam boiler. Pressure inside the tubes prevents the coolant from boiling. At the steam boiler, the heat from the coolant passes through the tube walls and heats up sea water. The sea water was pumped in from a nearby river or stream. The heated sea water boils into steam. The steam travels through pipes to a turbine. The steam causes a turbine to turn, which then turns a generator to create electricity. (Back to Generating page for more information) After the coolant releases its heat in the steam boiler, it circulates back around toward the reactor's core. A pump keeps the coolant circulating so that none of its radioactivity can escape.

If the core reaches the point where it is too hot, control rods are moved down into it. The control rods are made of an element that absorbs excess neutrons. When the control rods are moved into the core, they absorb neutrons, slowing down the chain reaction. When this happens less fission occurs and the heat is reduced.

USE

As of 2005, nuclear power provided 2.1% of the world's energy and 15% of the world's electricity, with the U.S., France, and Japan together accounting for 56.5% of nuclear generated electricity. In 2007, the IAEA reported there were 439 nuclear power reactors in operation in the world, operating in 31 countries.

In 2007, nuclear power's share of global electricity generation dropped to 14%. According to the International Atomic Energy Agency, the main reason for this was an earthquake in western Japan on 16 July 2007, which shut down all seven reactors at the Kashiwazaki-Kariwa Nuclear Power Plant. There were also several other reductions and "unusual outages" experienced in Korea and Germany. Also, increases in the load factor for the current fleet of reactors appear to have plateaued.

The United States produces the most nuclear energy, with nuclear power providing 19% of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors 78% as of 2006.In the European Union as a whole, nuclear energy provides 30% of the electricity.Nuclear energy policy differs between European Union countries, and some, such as Austria, Estonia, and Ireland, have no active nuclear power stations. In comparison, France has a large number of these plants, with 16 multi-unit stations in current use.

In the US, while the Coal and Gas Electricity industry is projected to be worth $85 billion by 2013, Nuclear Power generators are forecast to be worth $18 billion.

Many military and some civilian (such as some icebreaker) ships use nuclear marine propulsion, a form of nuclear propulsion. A few space vehicles have been launched using full-fledged nuclear reactors: the Soviet RORSAT series and the American SNAP-10A.

International research is continuing into safety improvements such as passively safe plants, the use of nuclear fusion, and additional uses of process heat such as hydrogen production (in support of a hydrogen economy), for desalinating sea water, and for use in district heating systems.

Flexibility of nuclear power plants

It is often claimed that nuclear stations are inflexible in their output, implying that other, typically fossil stations would be used to meet peak demand. Whilst it may have been true for certain reactors, this is not longer true of at least some modern designs. Nuclear plants are routinely used in load following mode on a large scale in France.

How much of the world's electricity comes from nuclear power?

Sixteen percent of the world's electricity is supplied by nuclear power, according to the World Nuclear Association. The electricity is produced by 440 nuclear reactors in 31 countries.

The United States has the most reactors with a total of 104, according to the International Atomic Energy Agency. The reactors are responsible for producing nearly 20 percent of the country's electricity.

The country that gets the highest percentage of its electricity from nuclear power is France. Its 59 reactors generate more than 78 percent of its electricity

How it works:

Nuclear power stations work in pretty much the same way as fossil fuel-burning stations, except that a "chain reaction" inside a nuclear reactor makes the heat instead.

The reactor uses Uranium rods as fuel, and the heat is generated by nuclear fission: neutrons smash into the nucleus of the uranium atoms, which split roughly in half and release energy in the form of heat.

Carbon dioxide gas or water is pumped through the reactor to take the heat away, this then heats water to make steam.

The steam drives turbines which drive generators. Video clip: Nuclear reactor

Modern nuclear power stations use the same type of turbines and generators as conventional power stations.

In Britain, nuclear power stations are often built on the coast, and use sea water for cooling the steam ready to be pumped round again. This means that they don't have the huge "cooling towers" seen at other power stations.

The reactor is controlled with "control rods", made of boron, which absorb neutrons. When the rods are lowered into the reactor, they absorb more neutrons and the fission process slows down. To generate more power, the rods are raised and more neutrons can crash into uranium atoms.

Natural uranium is only 0.7% "uranium-235", which is the type of uranium that undergoes fission in this type of reactor.

The rest is U-238, which just sits there getting in the way. Modern reactors use "enriched" uranium fuel, which has a higher proportion of U-235.

The fuel arrives encased in metal tubes, which are lowered into the reactor whilst it's running, using a special crane sealed onto the top of the reactor.

With an AGR or Magnox station, carbon dioxide gas is blown through the reactor to carry the heat away. Carbon dioxide is chosen because it is a very good coolant, able to carry a great deal of heat energy. It also helps to reduce any fire risk in the reactor (it's around 600 degrees Celsius in there) and it doesn't turn into anything nasty (well, nothing long-lived and nasty) when it's bombarded with neutrons.

You have to be very careful about the materials you use to build reactors - some materials will turn into horrible things in that environment. If a piece of metal in the reactor pressure vessel turns brittle and snaps, you're probably in trouble - once the reactor has been built and started you can't go in there to fix anything..

Uranium itself isn't particularly radioactive, so when the fuel rods arrive at the power station they can be handled using thin plastic gloves. A rod can last for several years before it needs replacing.

It's when the "spent" fuel rods are taken out of the reactor that you need the full remote-control robot arms and Homer Simpson equipment

Why use nuclear power?

Unlike burning fossil fuels, using nuclear fission to generate electricity produces no soot or greenhouse gases. This helps keep the skies clean and doesn't contribute to global warming. The World Nuclear Association estimates that the electricity industry would add 2.6 billion tons of carbon dioxide to the atmosphere each year if it used coal power instead of nuclear.

Some governments also like nuclear power because it reduces their dependency on foreign oil.

Finally, the fuel used to power nuclear reactors is very compact in comparison to fossil fuels. For instance, one pound of uranium can supply the same energy as 3 million pounds of coal. This makes it attractive for use in nuclear-powered vehicles like submarines, aircraft carriers and spacecraft.

How does a nuclear power plant produce electricity?

A nuclear power plant is basically a steam power plant that is fueled by a radioactive element, like uranium. The fuel is placed in a reactor and the individual atoms are allowed to split apart. The splitting process, known as fission, releases great amounts of energy. This energy is used to heat water until it turns to steam.

From here, the mechanics of a steam power plant take over. The steam pushes on turbines, which force coils of wire to interact with a magnetic field. This generates an electric current.

Why does splitting a uranium atom release energy?

The answer has to do with Einstein's most famous equation -- E=mc² -- which essentially says that energy is directly related to mass.

Under the right conditions, a uranium atom will split into two smaller atoms and throw off two or sometimes three neutrons in the process. (Neutrons are the glue that hold atoms together.)

The combined mass of these resulting particles tends to be roughly 99.9 percent of the mass of the original uranium atom. The other 0.1 percent of the original mass got converted to energy, as Einstein described.

The energy is released in the form of gamma rays. These rays are similar to X-rays and can cause burns, cancer and genetic mutations in living things. They can be slowed or stopped with thick walls of concrete, lead or packed dirt.

Where do the extra neutrons go when the atom splits?

The neutrons hit other atoms in the reactor core, starting a chain reaction. Initially, about 3 or 4 percent of the uranium atoms are uranium-235 -- the same as the first set of atoms that split. If these atoms are hit with neutrons, they split readily and throw off more energy and neutrons.

But the other 96 or 97 percent of the uranium atoms in the core initially are of a type that is hard to split, known as uranium-238. If hit with a neutron, a uranium-238 atom will absorb the neutron and eventually turn into plutonium-239. It's not until these plutonium atoms are hit again with more neutrons that they finally split and release energy.

Advantages

Nuclear power costs about the same as coal, so it's not expensive to make.

Does not produce smoke or carbon dioxide, so it does not contribute to the greenhouse effect.

Produces huge amounts of energy from small amounts of fuel.

Produces small amounts of waste.

Nuclear power is reliable.

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Disadvantages

Although not much waste is produced, it is very, very dangerous.

It must be sealed up and buried for many thousands of years to allow the radioactivity to die away.

For all that time it must be kept safe from earthquakes, flooding, terrorists and everything else. This is difficult.

Nuclear power is reliable, but a lot of money has to be spent on safety - if it does go wrong, a nuclear accident can be a major disaster.

People are increasingly concerned about this - in the 1990's nuclear power was the fastest-growing source of power in much of the world. In 2005 it was the second slowest-growing

Nuclear Waste

During fission, very harmful radiation rays are released. The most harmful of which are gamma rays. When the human body is exposed to radiation, it can cause tumors and can do extreme damage to the reproductive organs. For this reason, problems associated with radioactivity can be passed on to the victim's children as well. That is why radioactive waste produced by nuclear power plants is so dangerous.

After about 18 months in a reactor, fission begins to slow down, and the uranium rods must be replaced. It takes about 2 months to remove the old rods and place in the new ones. The used-up uranium rods are stuck in containers which are placed in swimming-pool sized tanks of water. In these tanks, the old rods lose some of their radioactivity and begin to cool down. However, many nuclear power plants are now running into the problem of their water tanks getting full of the rods, and are in need of a permanent storage place.

Many scientists have argued about a long term storage for our nuclear waste. Many think the waste should be placed in concrete containers and buried far beneath the Earth's surface. Others say that some of the waste should be loaded into rockets and shot at the sun. Some countries have already decided on their plans. Canada is currently looking at a plan to bury their radioactive waste underneath the Canadian Shield. The United States has a plan to bury their waste underground in Nevada where some nuclear experiments and tests have already been conducted. So far, continuing debates have prevented much of anything from being done about nuclear waste. Unfortunatelly, after buried underground, the nuclear waste can take millions of years to decay.

Nuclear reactor technology

Just as many conventional thermal power stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear power plants convert the energy released from the nucleus of an atom, typically via nuclear fission.

When a relatively large fissile atomic nucleus (usually uranium-235 or plutonium-239) absorbs a neutron, a fission of the atom often results. Fission splits the atom into two or more smaller nuclei with kinetic energy (known as fission products) and also releases gamma radiation and free neutrons. A portion of these neutrons may later be absorbed by other fissile atoms and create more fissions, which release more neutrons, and so on.