|Introduction to Nuclear Energy
When atoms split—or fission—they produce large amounts of energy, which is called nuclear energy. This energy is released in the form of heat. As the atom fragments hit other atoms, they also split, producing more heat. A nuclear power plant uses this heat to produce electricity. Currently nuclear power involves the controlled use of nuclear fission to release energy for work including propulsion, heat, and the generation of electricity.
Nuclear energy is one of the major forms of energy; this is the energy that is trapped inside each atom. One of the laws of the universe is that matter and energy can't be created nor destroyed. But they can be changed in form. Matter can be changed into energy. The world's most famous scientist, Albert Einstein, created the mathematical formula that explains this. It is: E = mc2
This equation says:
E [energy] equals m [mass] time’s c2 [c stands for the velocity or the speed of light. c2 means c times c, or the speed of light raised to the second power -- or c-squared.]
Scientists used Einstein's famous equation as the key to unlock atomic energy and also create atomic bombs.
The ancient Greeks also said that the smallest part of nature is an atom. But 2,000 years ago, they did not know about nature's even smaller parts. These are the parts that make an atom: the electron, proton, and neutrons. As you know, there are over 100 elements in the periodic table. The thing that makes each of those elements different is the number of electrons, protons, and neutrons. The protons and neutrons are always in the center of the atom. Scientists call the center of the atom the nucleus. The electrons are always found whizzing around the center in areas called orbital.
Nuclear power can come from the fission of uranium, plutonium or thorium or the fusion of hydrogen into helium. Today it is almost all uranium. The basic energy fact is that the fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.
Natural uranium is almost entirely a mixture of two isotopes, U-235 and U-238. U-235 can fission in a reactor, and U-238 can't to a significant extent. Natural uranium is 99.3 percent U-238 and 0.7 percent U-235.
Developments of Nuclear Energy
In 1934, physicist Enrico Fermi conducted experiments in Rome that showed neutrons could split many kinds of atoms. The results surprised even Fermi himself. When he bombarded uranium with neutrons, he did not get the elements he expected. The elements were much lighter than uranium.
In the fall of 1938, German scientists Otto Hahn and Fritz Strassman fired neutrons from a source containing the elements radium and beryllium into uranium (atomic number 92). They were surprised to find lighter elements, such as barium (atomic number 56), in the leftover materials.
These elements had about half the atomic mass of uranium. In previous experiments, the leftover materials were only slightly lighter than uranium.
Hahn and Strassman contacted Lise Meitner in Copenhagen before publicizing their discovery. She was an Austrian colleague who had been forced to flee Nazi Germany. She worked with Niels Bohr and her nephew, Otto R. Frisch. Meitner and Frisch thought the barium and other light elements in the leftover material resulted from the uranium splitting -- or fissioning. However, when she added the atomic masses of the fission products, they did not total the uranium's mass. Meitner used Einstein's theory to show the lost mass changed to energy. This proved fission occurred and confirmed Einstein's work.
In the 1950s it was discovered how to do this in hydrogen bombs by using ordinary nuclear fission bombs to set off the fusion of the hydrogen isotopes of deuterium and tritium. Projects were promptly started for doing this under less violent conditions. After 50 years, fusion reactors may be close to getting more fusion energy out of the reaction that has to be put in. Present proposals use deuterium and lithium-6, as do present hydrogen bombs. Both US and UK have nuclear energy research projects underway at the time but both were unsuccessful and no bombs were produced.
A major goal of nuclear research in the mid-1950 was to show that nuclear energy could produce electricity for commercial use. The first commercial electricity-generating plant powered by nuclear energy was located in Shipping port, Pennsylvania. It reached its full design power in 1957. Light-water reactors like shipping port use ordinary water to cool the reactor core during the chain reaction. They were the best design then available for nuclear power plants. Private industry became more and more involved in developing light-water reactors after shipping port became operational. Federal nuclear energy programs shifted their focus to developing other reactor technologies.
The U.S. had twice as many operating nuclear power plants as any other country in 1991. This was more than one-fourth of the world's operating plants. Nuclear energy supplied almost 22 percent of the electricity produced in the U.S. 31 other countries also had nuclear power plants in commercial operation or under construction. That is an impressive worldwide commitment to nuclear power technology.
During the 1990's, the U.S. faces several major energy issues and has developed several major goals for nuclear power, which are:
· To maintain exacting safety and design standards;
· To reduce economic risk;
· To reduce regulatory risk; and
· To establish an effective high-level nuclear waste disposal program.
Several of these nuclear power goals were addressed in the Energy Policy Act of 1992, which was signed into law in October of that year.
Research in other nuclear areas is also continuing in the 1990's. Nuclear technology plays an important role in medicine, industry, science, and food and agriculture, as well as power generation. For example, doctors use radioisotopes to identify and investigate the causes of disease. They also use them to enhance traditional medical treatments. In industry, radioisotopes are used for measuring microscopic thicknesses, detecting irregularities in metal casings And testing welds. Archaeologists use nuclear techniques to date prehistoric objects accurately and to locate structural defects in statues and buildings. Nuclear irradiation is used in preserving food. It causes less vitamin loss than canning, freezing, or drying.
Nuclear research has benefited mankind in many ways. But today, the nuclear industry faces huge, very complex issues. How can we minimize the risk? What do we do with the waste? The future will depend on the advanced engineering, scientific research, and the involvement of an enlightened citizenry.
How Nuclear Energy Works
1) Nuclear fission makes heat.
2) Heat water to make steam
3) Steam turns turbines
4) Turbines turn generators
5) Electrical power sent around the country.
Nuclear power stations work in 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 is pumped through the reactor to take the heat away, and the hot gas then heats water to make steam.
The steam drives turbines, which drive generators.
Modern nuclear power stations use the same type of turbines and generators as conventional power stations.
In Britain, nuclear power stations are built on the coast, and use seawater for cooling the steam ready to be pumped round again. This means that they don't have the huge "cooling towers" like 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.
How Nuclear Power is Generated
Nuclear power is derived from the enormous energy stored in an atom’s nucleus, which is composed of protons and neutrons. This energy is released through a process called fission, whereby the nucleus of a uranium atom is “shot” with an outside neutron and splits apart, releasing its neutrons, which in turn bombard other uranium atoms, resulting in a chain reaction. Nuclear power is created by capturing the heat from that chain reaction. Unlike power plants that burn fossil fuels (coal, oil, gas) and pollute the atmosphere with carbon dioxide, nuclear power is clean.
Before it can be used in the reactor, the uranium must first be mined, then milled by a leaching process to create uranium oxide called yellowcake, which is filtered and dried. The yellowcake is then converted to uranium hexafluoride, which is composed of two types of uranium: U-238 and U-235, the latter being the one that fissions most easily. To make it usable as fuel, it musts then be enriched to a higher concentration of U-235, from 1% to upwards of 5%. Once enriched, it is then processed into pellets and loaded into long, non-corrosive zirconium alloy tubes. A uranium pellet the size of your fingertip is capable of producing as much energy as 150 gallons of oil. The pellets are packed into 12 foot long vertical rods and inserte3d into the reactor, where the fission process takes place.
The heat generated created steam from water surrounding the tubes. The steam turns huge turbine blades, which drive a generator and creates electricity. The steam is then converted back to water in cooling towers and reused. Called boiling water reactors, they comprise one-third of the nation’s plants, the other two-thirds are pressurized water reactors, in which the water is heated short of the boiling point, pumped to a steam generator, and the heat from the water is transferred to a second water supply that is then boiled to make steam.
Advantages of Nuclear Energy
- The Earth has limited supplies of coal and oil. Nuclear power plants could still produce electricity after coal and oil become scarce.
- Nuclear power plants need less fuel than ones, which burn fossil fuels. One ton of uranium produces more energy than is produced by several million tons of coal or several million barrels of oil.
- Coal and oil burning plants pollute the air. Well-operated nuclear power plants do not release contaminants into the environment.
Other advantages include,
- Nuclear fuel is inexpensive
- Waste is highly compact, unlike carbon dioxide
- The compact fuel is easy to transport
Disadvantages of Nuclear Energy
- The problem of radioactive waste is still an unsolved one. The waste from nuclear energy is extremely dangerous and it has to be carefully looked after for several thousand years (10'000 years according to United States Environmental Protection Agency standards).
- Despite generally high securities standard, accidents can still happen. It is technically impossible to build a plant with 100% security. A small probability of failure will always last. The consequences of an accident would be absolutely devastating both for human being as for the nature.
- The more nuclear power plants are built, the higher is the probability of a disastrous failure somewhere in the world.
- Nuclear power plants as well as nuclear waste could be preferred targets for terrorist attacks. No atomic energy plant in the world could withstand an attack similar to 9/11 in Yew York. Such a terrorist act would have catastrophic effects for the whole world.
- Radioactive waste is produced during the operation of nuclear power plants, which in turn can be used for the production of nuclear weapons. In addition, the same know-how used to design nuclear power plants can to a certain extent be used to build nuclear weapons (nuclear proliferation).
- The energy source for nuclear energy is Uranium. Uranium is a scarce resource; its supply is estimated to last only for the next 30 to 60 years depending on the actual demand.
- The time frame needed for formalities, planning and building of a new nuclear power generation plant is in the range of 20 to 30 years in the western democracies.
Around the world, more than 400 nuclear plants are operating in 25 countries. They supply almost 17 percent of the world's electricity. In many countries, nuclear energy plays an even larger role than in the United States.
Many of these nations are building new nuclear energy plants, to meet the needs of their growing populations and expanding economies. Around the world, about 83 new nuclear energy plants are being built.
Common Discussion on Nuclear Energy
Is the use of nuclear absolutely essential to the sustainability of progress?
Probably not. Solar energy would also work, but at considerably greater cost if relied upon for most of the world's energy. While it is arguable that nuclear energy is not needed to progress, it is nonetheless there and far greater progress can be achieved with it.
What is likely to happen with nuclear energy?
The countries that need it the most will continue to use it. France gets 77 percent of its electricity from nuclear reactors, the rest being hydroelectric. Japan is close to 30 percent and increasing steadily. Japan has little domestic coal and no oil. We have plenty of coal and natural gas; can afford to import more than half of our oil. Therefore, we can afford delays caused by controversy unless we are zapped by the greenhouse effect. However, the counterculture generation is passing through the peak of its political power, and the next generations seem to be more rational about nuclear energy and many other issues.
Therefore, the U.S. is likely to resume building reactors before being driven to it by other countries getting economic advantages.
Then what about giving up on nuclear energy because of the danger of nuclear war?
Giving up on nuclear energy is unlikely to reduce the danger of nuclear wars. In fact it is likely to increase the danger, because of the advantage it would give to whoever would first reintroduce nuclear weapons. Also the poorer world that would result from the abandonment of nuclear energy would be more likely to have wars.
All this is well and good, but isn't the opposition to nuclear power strong enough to prevent its use?
Not when and if refusing to build a nuclear plant results in a substantial loss of a country's standard of living. Politicians seem to believe that mentioning nuclear energy is political poison at present. They may be right or it may be just one more superstition prevalent among politicians and their consultants. Recently a taboo against mentioning nuclear energy has developed among scientists - especially those specializing in energy. None of the articles in the recent special issue of Science devoted to energy mentioned nuclear energy - pro or con - even though nuclear energy provides 17 percent of American electricity. Perhaps energy scientists feel that mentioning nuclear energy will have an adverse effect on their grants. Perhaps there is some other reason. To some extent "hydrogen" in the energy literature is a code word for nuclear energy, since many articles promoting hydrogen don't say how else it can be generated economically in the quantities required to run an economy. Recent waves of ideology are strongly involved.
Why is reprocessing still not being done?
Although not a new technology, reprocessing can be part of the solution to nuclear waste. When nuclear power was first developed, it was assumed that spent nuclear fuel would go through a process called reprocessing. In reprocessing, one of the major transuranic wastes, 239Pu, is extracted from the spent fuel rods. This 239Pu (plutonium-239) is fissile and can be reused in power plants. The advantages of this process are somewhat obvious: The volume of waste is lessened and more fuel is created for nuclear reactors. However, as with all things, politics can get in the way. In the US plutonium reprocessing was banned because the recovered 239Pu is weapons grade material. If, after reprocessing, the fuel is stolen, it could be used by anyone to construct a nuclear weapon. As of a few years ago, the ban against reprocessing in the US was lifted, but there are still no operating reprocessing plants in the US because of the heavy regulations and the anti-nuclear sentiment of the general public. There are a few countries, which do reprocessing, however. France, for instance, regularly reprocesses its spent fuel.
Is producing nuclear energy expensive?
It is in fact one of the least expensive energy sources. In 2004, the average cost of producing nuclear energy in the United States was less than two cents per kilowatt-hour, comparable with coal and hydroelectric. Advances in technology will bring the cost down further in the future.