21. EUROPA - Research - Energy - - Fission Energy And Radiation Protection Research nuclear fission energy contributes successfully to meeting a large part of the evergrowing demand of energy world-wide. nuclear power supplies a third of http://europa.eu.int/comm/research/energy/fi/article_1121_en.htm

en EUROPA European Commission Energy Fission Energy and Radiation Protection Research ... Print version Fission Energy and Radiation Protection Research Understanding the Science Research Topics Current Programme Activities Links ... Projects' press releases Fission energy and radiation protection research helps exploit the full potential of nuclear fission energy. It is carried out in the European Union (EU) as a part of the 'Research and Training Programme in the field of Nuclear Energy' within the Framework Programmes of the European Atomic Energy Community (EURATOM). Fission energy Nuclear fission energy contributes successfully to meeting a large part of the ever-growing demand of energy world-wide. Nuclear power supplies a third of the EU's electricity and does not emit any greenhouse gases. Nuclear energy enables the EU to reduce its greenhouse gas emissions by 7% a year - the equivalent of the carbon dioxide (CO ) emissions produced by some 75 million cars. Thus, nuclear power contributes significantly to

22. Nuclear Energy Is The Most Certain Future Source. Here s a new page on nuclear energy Now. It is motivated by the Bush nuclear power can come from the fission of uranium, plutonium or thorium or the http://www-formal.stanford.edu/jmc/progress/nuclear-faq.html

FREQUENTLY ASKED QUESTIONS ABOUT NUCLEAR ENERGY by John McCarthy This page discusses nuclear energy as a part of a more general discussion of why human material progress is sustainable and should be sustained. Energy is just one of the questions considered. Up to: Main page on why progress is sustainable Incidentally, I'm Professor of Computer Science at Stanford University, emeritus (means retired) as of 2001 January 1. Here's my main page . I write about sustainability as a volunteer public service. I am not professionally involved with nuclear energy. Here's a new page on Nuclear Energy Now . It is motivated by the Bush Administration in the U.S. having tentatively re-opened the question of building new nuclear plants in the U.S. I hope they persist and are successful. One of the major requirements for sustaining human progress is an adequate source of energy. The current largest sources of energy are the combustion of coal, oil and natural gas. These are discussed in the main page on energy . They will last quite a while but will probably run out or become harmful in tens to hundreds of years. Solar energy will also work but is not much developed yet except for special applications because of its high cost. This high cost as a main source, e.g. for central station electricity, is likely to continue, and nuclear energy is likely to remain cheaper. A major advantage of nuclear energy (and also of solar energy) is that it doesn't put carbon dioxide (CO2) into the atmosphere. How much of an advantage depends on how bad the CO2 problem turns out to be.

23. Nuclear Power - Wikipedia, The Free Encyclopedia All current nuclear power plants are critical fission reactors, which are the focus Proponents also note that nuclear power provides steady energy at a http://en.wikipedia.org/wiki/Nuclear_power

Nuclear power From Wikipedia, the free encyclopedia. The neutrality of this article is disputed Please see discussion on the talk page This article is about power derived from nuclear reactions . For countries that possess nuclear weapons see: Nuclear powers Nuclear power is the use of sustained nuclear reactions to do useful work (in the past, this was called Atomic Energy ). Currently, Nuclear power is generated by nuclear fission reactions which occur when sufficient amounts of uranium -235 and/or plutonium are confined to a small space, often in the presence of a neutron moderator . The reaction produces heat which is converted to kinetic energy by means of a steam turbine and then a generator for electricity production. Nuclear power currently provides about 17% of the world's electricity and 7% of global energy. An international effort into the use of nuclear fusion for power is ongoing, but not expected to be available in commercially viable form for several decades. After a period of decline following the Three Mile Island accident and the incident at Chernobyl , there is a recently renewed interest in nuclear energy because it could partially address both dwindling oil reserves and global warming with fewer emissions of greenhouse gases than fossil fuel.

24. Nuclear Reactor - Wikipedia, The Free Encyclopedia Currently all commercial nuclear reactors are based on nuclear fission for The amount of energy in the reservoir of nuclear fuel is frequently http://en.wikipedia.org/wiki/Nuclear_reactor

Nuclear reactor From Wikipedia, the free encyclopedia. A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion , where the chain reaction occurs in a split second). Nuclear reactors are used for many purposes, but the most significant current uses are for the generation of electrical power and, in rare cases, for the production of plutonium for use in nuclear weapons . Currently all commercial nuclear reactors are based on nuclear fission , and are considered problematic for their safety and health risks. Experiments in fusion power seek to replace nuclear fission reactors with nuclear fusion reactors. There are other devices in which nuclear reactions occur in a controlled fashion, including radioisotope thermoelectric generators , which generate heat and power by passive radioactive decay, and Farnsworth-Hirsch fusors , in which controlled nuclear fusion is used to produce neutron radiation A nuclear power station. The nuclear reactors are inside the cylindrical containment buildings in the foreground - behind are the cooling towers (venting steam).

25. The Energy Story Chapter 7 nuclear energy fission and Fusion. Another major form of energy is nuclear energy, the energy that is trapped inside each atom. http://www.hamburger-bildungsserver.de/klima/energie/energy/energy-118.html

The Energy Story Chapter 7: Nuclear Energy - Fission and Fusion Another major form of energy is nuclear energy, 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 famous scientist Albert Einstein created the mathematical formula that explains this. It is: E = mc This equation says: E [energy] equals m [mass] times c [c stands for the speed of light. c means c times c, or the speed of light raised to the second power or c-squared.] Please note that some web browser software may not show an exponent (raising something to a power, a mathematical expression) on the Internet. Normally c-squared is shown with a smaller "2" placed above and to the right of the c. Scientists used Einstein's famous equation as the key to unlock atomic energy and also create atomic bombs. The ancient Greeks said the smallest part of nature is an atom. But they did not know 2,000 years ago about nature's even smaller parts. As we learned in chapter 2 , atoms are made up of smaller particles a nucleus of protons and neutrons, surrounded by electrons which swirl around the nucleus much like the earth revolves around the sun.

26. (S-8) Nuclear Energy Elementary review of the generation of energy by nuclear fission; a sideexcursion in an educational web site on astronomy, mechanics, and space. http://www-spof.gsfc.nasa.gov/stargaze/Snuclear.htm

Site Map (S-8) Nuclear Power Note: This is a side-excursion into the basics of nuclear energy Bear in mind that even without math, this can be a fairly difficult subject and that the discussion is rather lengthy. The ideas from section S-7 are reviewed in what follows next. The rest of the section is a qualitative discussion of all key processes involved in the practical use nuclear energy. A Review of Nuclear Structure The way the Sun generates its energy helps understand the way a nuclear power station does so. The two processes are however quite different. Here some facts about the way protons and neutrons combine to form nuclei, as covered in section S-7 about the Sun: helium Unlike gravity or electrical forces, the nuclear force is effective only at very short distances. At greater distances, the protons repel each other because they are positively charged, and charges of the same kind repel. For that reason, the protons forming the nuclei of ordinary hydrogenfor instance, in a balloon filled with hydrogendo not combine to form helium (a process which also would require some to combine with electrons and become neutrons). They cannot get close enough for the nuclear force, which attracts them to each other, to become important! Only in the core of the Sun, under extreme pressure and temperature, can such a process take place. Other small nuclei can similarly combine into bigger ones and release energy, but in combining such nuclei, the amount of energy released is much smaller. The reason is that while the process

27. Nuclear Energy nuclear energy plants produce electricity through the fission of uranium, not the burning of fuels. Consequently, nuclear power plants do not pollute the http://www.umich.edu/~gs265/society/nuclear.htm

Jon Stone Introduction Only 30 years ago, nuclear energy was an exotic, futuristic technology, the subject of experimentation and far fetched ideas. Today, nuclear energy is America's second largest source of electric power after coal. More than 110 nuclear energy plants supply more electricity than oil, natural gas or hydropower. Since 1973, they have saved American consumers approximately $44 billion, compared to the other fuels that would have been used to make electricity. Since our electricity system is interconnected, practically every American gets some electricity from nuclear energy. In addition to the economic benefits achieved through the use of nuclear energy, there are environmental benefits as well. There are, however, various drawbacks caused by the production of electricity through nuclear power. Although there are various risks involved when using nuclear energy as a source of power, we argue that the benefits greatly outweigh any potential problems that may arise. Nuclear Reactors and Their Fuel Cycles The use of nuclear reactors to generate electricity continues to increase all over the world. By December of 1979, about 128,000 million watts were being generated by 249 reactors operating in 22 countries.

28. Nuclear Chemistry nuclear energy for Power and Weapons The energy released by fission excited the European scientists who discovered the phenomenon. http://www.chemcases.com/nuclear/

Nuclear Chemistry and the Community Dr. Frank Settle Nuclear Science in: two 45 minute classes , or a quick review for interested learners, or A complete review and case study of nuclear chemistry Discovery of the Neutron Playing with Neutrons(1934-38) Discovery of Fission(1938) Discovery of Pu-239(1941) ... Case Study Visit the complete source for nuclear science information Goals: In this session you will be introduced to: Merlexi Craft: See http://merlexi.com The relationship of energy and matter The origins of nuclear energy The use of nuclear energy for power and weapons High energy radiation How spent nuclear power fuels are potential sources of nuclear weapons Insight into questions about nuclear issues that are in the news during these times of unrest. Albert Einstein as Memorialized at the US National Academy of Sciences Energy and Matter: Nuclear science began with Albert Einstein who recognized that matter and energy were equivalent. We have all heard the equation: E=mc This was Einstein's understanding at the beginning of the last century. Energy - the ability to provide heat or do work, had an equivalency with matter - the mass of the physical universe. The relationship was astonishing in that the amount of energy equivalent to a given amount of matter was related by the square of the speed of light. The equation predicted that IF matter could be converted to energy in a practical manner, a very small amount of matter would generate enormous amounts of energy.

29. Fission And Fusion If a large nucleus is split apart (fission), generous amounts of energy can be fission is a nuclear reaction in which an atomic nucleus splits, http://reactor.engr.wisc.edu/fission.htm

College of Engineering University of Wisconsin - Madison University of Wisconsin Nuclear Reactor Tour Nuclear Energy Atoms are the building blocks from which matter is formed. Everything around us is made up of atoms. Nuclear energy is contained within the center of the atom in a place known as the nucleus . Particles within the nucleus are held together by a strong force. If a large nucleus is split apart (fission) , generous amounts of energy can be liberated. Small nuclei can also be combined (fusion) with an accompanying release of energy. Using this strong force that holds the nucleus together to produce energy is essentially what the field of nuclear power generation is about. In the fission process certain heavy elements, such as some forms of Uranium , are split when a neutron strikes them. When they split, they release energy in the form of kinetic energy (heat) and radiation . The process not only produces energy but also additional neutrons that can be used to fission other Uranium nuclei and start a chain reaction.

30. NRC: Students' Corner nuclear energy is a way to generate heat using the fission process of atoms. A nuclear power plant converts the heat into electricity. http://www.nrc.gov/reading-rm/basic-ref/students.html

Home Electronic Reading Room Basic References NRC Home Page Students' Corner Teachers' Lesson Plans About NRC Glossary of Nuclear Terms Basic References ... Games Nuclear energy is a way of creating heat through the fission process of atoms. All power plants convert heat into electricity using steam. At nuclear power plants, the heat to make the steam is created when atoms split apart called fission. (Other types of power plants burn coal or oil for heat to make steam.) The fission process takes place when atoms are split into small pieces by neutrons hitting each other. These smaller pieces hit other atoms. This releases energy in the form of heat. When this process continues, it is called a chain reaction. In a nuclear power plant, uranium is the material used in the fission process. The heat from fission boils water and creates steam to turn a turbine. As the turbine spins, the generator turns and its magnetic field produces electricity. The electricity can then be carried to your home, so you can work on the computer, watch television, play video games, or make toast! When uranium a nuclear material is used as fuel in a nuclear power plant, the fission process creates heat, which boils water, creating steam. The steam turns a turbine that is connected to a generator.

31. NRC: Lesson Plans - Unit 3: Nuclear Reactors/Energy Generation To understand how the NRC regulates commercial nuclear energy. Today, we re going to talk about one of those ways nuclear fission. http://www.nrc.gov/reading-rm/basic-ref/teachers/unit3.html

Home Electronic Reading Room Basic References Teachers' Lesson Plans ... Games Links to Other Units Unit 1 - Radiation Unit 2 - The Uses of Radiation Unit 3 - Nuclear Reactors/Energy Generation Unit 4 - Radioactive Waste Unit 5 - Transportation of Radioactive Materials Objectives Questions ... Classroom Activities Time: Three hours Objectives A. Teacher: To ensure students understand how nuclear energy is generated. To help students learn how a nuclear power plant works. To understand how the NRC regulates commercial nuclear energy. B. At the conclusion of this unit the student should be able to Describe the fission process. Identify the various kinds of nuclear power plants. Discuss the process of energy generation with nuclear power plants. Investigation and Building Background 1. Introduce term: Students have little knowledge of nuclear reactors and limited understanding of the terminology used in nuclear power plants. Definitions found in dictionaries tend to be vague regarding this specialized language. 2. School resources:

32. MSN Encarta - Nuclear Energy nuclear energy is also released when the fission of a heavy nucleus such as ¯U A nuclear fission reaction releases 10 million times as much energy as is http://encarta.msn.com/encyclopedia_761558960/Nuclear_Energy.html

MSN Home My MSN Hotmail Shopping ... Sign In Web Search: Encarta Subscriber Sign In Help Home ... Upgrade your Encarta Experience Search Encarta Upgrade your Encarta Experience Spend less time searching and more time learning. Learn more Tasks Find in this article Print Preview Related Items Nuclear Weapons, explosive devices designed to release nuclear energy Plutonium, used as fuel in nuclear reactors more... Further Reading Editors' picks for Nuclear Energy Search for books and more related to Nuclear Energy Encarta Search Search Encarta about Nuclear Energy Editors' Picks Great books about your topic, Nuclear Energy ... Click here Advertisement document.write(' Nuclear Energy Encyclopedia Article Multimedia 10 items Article Outline Introduction The Atom Nuclear Energy from Fission Nuclear Power Reactors ... Nuclear Fusion I Introduction Print Preview of Section Nuclear Energy , energy released during the splitting or fusing of atomic nuclei. The energy of any system, whether physical, chemical, or nuclear, is manifested by the system’s ability to do work or to release heat or radiation. The total energy in a system is always conserved, but it can be transferred to another system or changed in form. Until about 1800 the principal fuel was wood, its energy derived from solar energy stored in plants during their lifetimes. Since the Industrial Revolution, people have depended on fossil fuels—coal, petroleum, and natural gas—also derived from stored solar energy. When a fossil fuel such as coal is burned, atoms of hydrogen and carbon in the coal combine with oxygen atoms in air. Water and carbon dioxide are produced and heat is released, equivalent to about 1.6 kilowatt-hours per kilogram or about 10 electron volts (eV) per atom of carbon. This amount of energy is typical of chemical reactions resulting from changes in the electronic structure of the atoms. A part of the energy released as heat keeps the adjacent fuel hot enough to keep the reaction going.

33. Nuclear Energy nuclear fission is also the process responsible for the large energy release in an A problem with energy from nuclear fission is that it is not clean, http://staff.science.nus.edu.sg/~parwani/htw/c2/node49.html

Next: Hydroelectric Power Up: Our Energy Sources Previous: Solar Energy Contents Nuclear Energy Nuclear fission currently supplies about of the world's energy needs, and it is likely that this source will be dominant as fossil fuels run out. The basic origin of this energy is Einstein's relation between mass and energy. In nuclear fission, an atom of Uranium splits after absorbing a slow neutron, into a number of smaller fragments. The total mass of the end products is less than the mass of the initial reactants, and the difference is precisely the produced energy. The large value of the speed of light means that, by , even a small mass can be converted into a large amount of energy. For example, the total fission of one kilogramme of Uranium can provide the same energy as that released by burning three million kilogrammes of coal! Nuclear fission is also the process responsible for the large energy release in an atomic bomb. The difference between an atomic bomb and a nuclear reactor is that in the latter the energy is released in a controlled manner. A problem with energy from nuclear fission is that it is not clean, as radioactive waste products are produced which must be disposed off somewhere. In principle one can produce energy also from nuclear fusion : When two atoms combine to form a bigger atom, the final product has less mass than the sum of original masses and again the difference is converted to energy. However although this is a cleaner resource than fission, and though the main ingredient, deuterium is plentiful in sea-water, fusion is far from a reality now because of various technological hurdles, and it is unclear if these will be overcome for it to be practical in the forseable future. Amusingly though, we are the beneficiaries of nuclear fusion: The Sun produces its energy by fusing hydrogen into helium under conditions of extreme temperature and pressure. The Sun will continue to provide energy until it dies some five billion years from now.

34. Nuclear Energy nuclear energy from fission and fusion. nuclear power is generated either through fusion or through fission. fission is the splitting of a heavy nucleus http://www.pa.msu.edu/courses/1997spring/PHY232/lectures/nuclear/bombs.html

Nuclear energy from fission and fusion Nuclear power is generated either through fusion or through fission. Fission is the splitting of a heavy nucleus into light nuclei which are more energetically favorable. Since Iron-56 is the most energetically favorable nucleus, both the fission of heavy nuclei and the fusion of light nuclei can release energy. Fission is the process used in the first nuclear weapons and in power plants. Fusion is the source of the sun's energy and is the source of energy in hydrogen bombs. Fusion is an inherently cleaner source of energy, but igniting it in a controlled way has proved problematic. (hydrogen bombs are set off by fission devices). Fission is set off by bringing together a critical mass of an element such as Uranium-235. If a sufficient amount of Uranium is brought together an emitted neutron will most likely be captured, changing the Uranium to U-236, rather than escaping from the surface. Since U-236 decays and produces 2 neutrons, the number of neutrons grows exponentially, and practically all the U-235 nuclei decay in short order. This is called a chain reaction . In a power plant the chain reaction is modified with neutron absorbing rods. Examples Nuclear physics' index

35. Accelerator-driven Systems The essence of a conventional nuclear reactor is the controlled fission chain reaction of Boldeman, JW, 1997, Accelerator driven nuclear energy systems, http://www.uic.com.au/nip47.htm

Accelerator-driven Nuclear Energy Nuclear Issues Briefing Paper 47 August 2003 Powerful accelerators can produce neutrons by spallation. This process may be linked to conventional nuclear reactor technology in Accelerator-Driven Systems (ADS) to transmute heavy isotopes in spent nuclear fuel into shorter-lived fission products. There is also increasing interest in the application of ADS to running subcritical nuclear reactors, powered by thorium. The essence of a conventional nuclear reactor is the controlled fission chain reaction of U-235 and Pu-239. This produces heat which is used to make steam which drives a turbine. The chain reaction depends on having a surplus of neutrons to keep it going (a U-235 fission requires one neutron input and produces on average 2.43 neutrons). For many years there has been interest in utilising thorium (Th-232) as a nuclear fuel since it is three times as abundant in the earth's crust as uranium. Also, all of the mined thorium is potentially useable in a reactor, compared with the 0.7% of natural uranium, so some 40 times the amount of energy per unit mass might be available. A thorium reactor would work by having Th-232 capture a neutron to become Th-233 which decays to uranium-233, which fissions. The problem is that insufficient neutrons are generated to keep the reaction going. More recently there has been interest in transmuting the long-lived transuranic radionuclides (actinides - neptunium, americium and curium particularly) formed by neutron capture in a conventional reactor and reporting with the high-level waste. If these could be made into shorter-lived radionuclides such as fission products, the management and eventual disposal of high-level radioactive waste would be easier and less expensive. As it is, most radionuclides (notably fission products) decay rapidly, so that their collective radioactivity is reduced to less than 0.1% of the original level 50 years after being removed from the reactor. However, the main long-lived ones are actinides.

36. Safety Of Nuclear Power Reactors The use of nuclear energy for electricity generation can be considered extremely in power output from the fission process ( positive void coefficient). http://www.uic.com.au/nip14.htm

Safety of Nuclear Power Reactors Nuclear Issues Briefing Paper 14 November 2003 From the outset, there has been a strong awareness of the potential hazard of both nuclear criticality and release of radioactive materials. There have been two major reactor accidents in the history of civil nuclear power - Three Mile Island and Chernobyl. One was contained and the other had no provision for containment. These are the only major accidents to have occurred in over 11 000 cumulative reactor-years of commercial operation in 32 countries. The risks from western nuclear power plants, in terms of the likelihood and consequences of an accident or terrorist attack, are minimal compared with other commonly accepted risks. The operation of many nuclear reactors in the former Eastern Bloc is of international concern, and a program of international assistance is helping to improve their safety. There have been two major accidents in the history of civil nuclear power generation; Three Mile Island (USA 1979) where the reactor was severely damaged but radiation was contained and there were no adverse health or environmental consequences Chernobyl (Ukraine 1986) where the destruction of the reactor by explosion and fire killed 31 people and had significant health and environmental consequences.

37. Nuclear Energy of what we have learned so far so as to understand the basic facts. There are two kinds of ways that nuclear energy has been used fission and fusion. http://zebu.uoregon.edu/~soper/Sun/earthnuke.html

Nuclear energy on Earth Nuclear processes can release a million times the energy of a chemical process. For this reason, mankind has tried to make use of this energy source for both military purposes and for power production. Both purposes involve very significant issues of public policy. Exploring these issues would take us too far from study of stars, but we should at least take advantage of what we have learned so far so as to understand the basic facts. There are two kinds of ways that nuclear energy has been used: fission and fusion. Fission Fission involves very heavy nuclei. The big nucleus absorbs a neutron and breaks up, releasing more neutrons. The most important reactions are U + n > two smaller nuclei + more n's naturally occuring uranium is mostly U U is separated from the U with a difficult process. Pu + n > two smaller nuclei + more n's Pu does not occur naturally it can be made in reactors U + n > two smaller nuclei + more n's U does not occur naturally it can be made in reactors Each of these reactions release about 200 MeV of energy.

38. Nuclear Energy: Nuclear Fission The development of nuclear energy from fission reactions began with the program to produce atomic weapons in the United States. Early work was carried out http://www.factmonster.com/ce6/sci/A0860068.html

Home U.S. People Word Wise ... Homework Center Fact Monster Favorites Hurricane Katrina Ramadan Children Inventors The Doctor's In ... 2006 TFK Almanac Reference Desk Atlas Almanacs Dictionary Encyclopedia ... nuclear energy Nuclear Fission The process of nuclear fission was discovered in 1938 by Otto Hahn and Fritz Strassmann and was explained in early 1939 by Lise Meitner and Otto Frisch. The fissionable isotope Since this reaction also releases an average of 2.5 neutrons, a chain reaction is possible, provided at least one neutron per fission is captured by another nucleus and causes a second fission. In an atomic bomb , the number is greater than 1 and the reaction increases rapidly to an explosion. In a nuclear reactor , where the chain reaction is controlled, the number of neutrons producing additional fission must be exactly 1.0 in order to maintain a steady flow of energy. Uranium-235, which occurs naturally as one part in 140 in a natural mixture of uranium isotopes, is not the only material fissionable by thermal neutrons. Uranium-233 and plutonium-239 can also be used but must be produced artificially. Uranium-233 is produced from thorium-232, which absorbs a neutron and then undergoes beta decay (the loss of an electron). Plutonium-239 is produced in a similar manner from uranium-238, which is the most common isotope of natural uranium. The average energy released by the fission of uranium-235 is 200 million electron volts, and that released by uranium-233 and plutonium-239 is comparable. Fission can also occur spontaneously, but the time required for a heavy nucleus to decay spontaneously by fission (10 million billion years in the case of uranium-238) is so long that induced fission by thermal neutrons is the only practical application of nuclear fission. However, spontaneous fission of uranium can be used in the

39. Nuclear Reactors A nuclear reactor operates by the controlled fission of 235U. fission occurs at a The energy of fission appears in the form of the motion of fission http://academic.brooklyn.cuny.edu/physics/sobel/Nucphys/pile.html

Controlled Fission A nuclear reactor operates by the controlled fission of U. Fission occurs at a slow steady rate, rather than suddenly in a fraction of a second, as in a bomb. Fission produces heat, and this heat is used to generate electricity, in the same way that the heat of burning oil or coal generates electricity in a conventional power plant. Continuous operation depends on each fission producing neutrons for the next fissions. But we do not look for the multiplying effect. Rather, after each fission we want to produce, on the average, one additional neutron to initiate another fission. In that way the process doesn't grow rapidly, but continues at a constant rate. Operation It is not economically practical to generate electricity using highly enriched uranium. Some reactors operate with natural uranium (0.7% U), some with slightly enriched uranium (3% U). Since weapons require about 90% U, the uranium used in reactors cannot be diverted to weapons use. Slow Neutrons The presence of large amounts of U in the reactor imposes important constraints on the reactor's design. As neutrons collide with the

40. Nuclear Energy This is how the sun produces energy. In nuclear fission, energy is released when the nuclei of atoms are split apart. nuclear fission is the only method http://lsa.colorado.edu/essence/texts/nuclear.htm

1. What Is Nuclear Energy? Nuclear energy is energy that comes from the nucleus (core) of an atom. Atoms are the particles that make up all objects in the universe. Atoms consist of neutrons, protons, and electrons. Nuclear energy is released from an atom through one of two processes: nuclear fusion or nuclear fission. In nuclear fusion, energy is released when the nuclei of atoms are combined or fused together. This is how the sun produces energy. In nuclear fission, energy is released when the nuclei of atoms are split apart. Nuclear fission is the only method currently used by nuclear plants to generate electricity. The fuel most widely used by nuclear power plants for fissioning is uranium. Uranium is the heaviest of the 92 naturally occurring elements and is classified as a metal. It is also one of the few elements that is easily fissioned. Uranium was formed when the earth was created and is found in rocks all over the world. Rocks that contain a lot of uranium are called uranium ore, or pitch-blende. Uranium, although abundant, is a nonrenewable energy source. Two forms (isotopes) of uranium are found in nature, uranium-235 and uranium-238. These numbers refer to the number of neutrons and protons in each atom.

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