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.
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.
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.
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.
There are two other kinds of nuclear power plants that I am going to explain. These two are a fission power plant that uses a breeder reactor, and a fusion power plant.
Another kind of fission reactor is the breeder reactor. A breeder power plant runs the exact same way as a Light-Water power plant described above, except it uses plutonium, instead of uranium, as its fuel. After the plutonium has been taken from the core of the reactor, it can be reprocessed. The plutonium is sent to a reprocessing plant where it is reprocessed and recycled. After this, it is sent back to the nuclear power plant and can be used in the reactor again.
Each time the plutonium is reprocessed, more and more energy is drawn from it, and after many years it reaches a point where it can not be used anymore. Power plants which use plutonium as fuel would have a lower cost because of the small amount of fuel needed. Reprocessing also helps out with our problem of nuclear waste. The United States does not use breeder reactors. President Carter shut down the program because he was afraid that terrorists would get a hold of a sample of plutonium. Plutonium, unlike uranium, can be used in making atomic bombs.
Fusion is the exact opposite process of fission. In fusion, the nuclei of two atoms combine to form one atom, unlike fission where the nucleus of one atom is split into two. Fusion is the same process that takes place deep within the core of the sun. The one major plus of fusion plants is that they release absoluteley no radiation. Very intense heat levels are needed for fusion to occur. That is why it is so hard to use. The energy it takes to run a fusion power plant is about the same as what is produced.
Although nuclear power plants have many advantages, they have some major problems. If anything were ever to go wrong inside the reactor, the results could be disasterous. One of the most dangerous difficulties is the possibility of a nuclear meltdown. This occurs when the core overheats in an uncontrolled manner -- the core simply melts. Such an event would release amazing amounts of radioactivity. There are many emergency cooling systems and back-ups to prevent the reactor from getting to meltdown temperatures.
One problem that was not stopped was the incident at Chernobyl. The Chernobyl plant reached 150 times its normal power level. The pressure inside the water holding tubes there became so great that finally the plant just blew itself apart. Poor construction and operation of the power plant caused the disaster. The disaster killed 31 people and 20 square miles of land are now uninhabitable. Some people say that the Chernobyl accident is responsible for many cases of cancer all across Europe. The scientists and environmentalists fighting against nuclear power, use accidents like these as their argument.
Scientists all over the world are debating about nuclear power, and whether or not it is safe to be used. Over 100 nuclear power plants now produce 20% of the United States' electricity, but the industry has stopped growing. Nuclear generated electricity is losing it's financial advantage over coal-powered electricity. Nuclear power plants still have the advantages of fuelcosts and no air or water pollution. The future of nuclear power is hard to predict. Will it become the most widely used source of electricity, or will it's disadvantages overcome these advantages?
Our References Were:
The Economics of Nuclear Power (web page)
1993 Uranium Institute Symposium Abstract (web page)
Frequently Asked Questions About Nuclear Energy (web page) at http://iip.ucsd.edu/step/projects95/Nuclear.Issues/nuclear.html