Nuclear technology 97830 225066956 2008-07-11T18:52:32Z VolkovBot 3035831 robot Modifying: [[fa:فن‌آوری هسته‌ای]] {{Refimprove|article|date=November 2006}} [[Image:Ceiling-smoke-alarm.JPG|thumb|right|200px|A residential [[smoke detector]] is for most people the most familiar piece of nuclear technology]] '''Nuclear technology''' is technology that involves the [[nuclear reaction|reactions]] of [[atomic nucleus|atomic nuclei]]. It has found applications from [[smoke detector]]s to [[nuclear reactor]]s, and from [[gun sight]]s to [[nuclear weapon]]s. There is a great deal of public concern about its possible implications, and every application of nuclear technology is reviewed with care. ==History == === Discovery === In 1896, [[Henri Becquerel]] was investigating [[phosphorescence]] in [[uranium]] salts when he discovered a new phenomenon which came to be called [[radioactivity]].<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel-bio.html Henri Becquerel]</ref> He, [[Pierre Curie]] and [[Marie Curie]] began investigating the phenomenon. In the process they isolated the element [[radium]], which is highly radioactive. They discovered that radioactive materials produce intense, penetrating rays of several distinct sorts, which they called [[alpha particle|alpha rays]], [[beta particle|beta rays]] and [[gamma ray]]s. Some of these kinds of radiation could pass through ordinary matter, and all of them could cause damage in large amounts - all the early researchers received various [[radiation burn]]s, much like [[sunburn]], and thought little of it. The new phenomenon of radioactivity was seized upon by the manufacturers of [[quack medicine]] (as had the discoveries of [[electricity]] and [[magnetism]], earlier), and any number of [[patent medicine]]s and treatments involving radioactivity were put forward. Gradually it came to be realized that the radiation produced by radioactive decay was [[ionizing radiation]], and that quantities too small to burn presented a severe long-term hazard. Many of the scientists working on radioactivity died of [[cancer]] as a result of their exposure. Radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters. As the [[atom]] came to be better understood, the nature of radioactivity became clearer; some atomic nuclei are unstable, and can decay releasing energy (in the form of: [[gamma ray]]s, high-energy [[photon]]s); ([[alpha particle]]s, a pair of [[proton]]s and a pair of [[neutron]]s; and [[beta particle]]s, high-energy [[electron]]s). === Nuclear fission === Radioactivity is generally a slow and difficult process to control, and is unsuited to building a weapon. However, other nuclear reactions are possible. In particular, a sufficiently unstable nucleus can undergo [[nuclear fission]], breaking into two smaller nuclei and releasing energy and some [[fast neutron]]s. This neutron could, if captured by another nucleus, cause that nucleus to undergo fission as well. The process could then continue in a nuclear [[chain reaction]]. Such a chain reaction could release a vast amount of energy in a short amount of time. When discovered on the eve of [[World War II]], it led multiple countries to begin programs investigating the possibility of constructing an [[atomic bomb]]—a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. The [[Manhattan Project]], run by the United States with the help of the United Kingdom and Canada, developed multiple fission weapons which were used against Japan in 1945. During the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate power. === Nuclear fusion === {{main|Timeline of nuclear fusion}} Nuclear fusion technology was initially pursued only in theoretical stages during World War II, when scientists on the Manhattan Project (led by [[Edward Teller]]) investigated the possibility of using the great power of a fission reaction to ignite fusion reactions. It took until 1952 for the first full detonation of a [[hydrogen bomb]] to take place, so-called because it utilized reactions between [[deuterium]] and [[tritium]], isotopes of [[hydrogen]]. Fusion reactions are much more energetic per unit mass of fusion material, but it is much more difficult to ignite a chain reaction than is fission. Research into the possibilities of using nuclear fusion for civilian power generation was begun during the 1940s as well. Technical and theoretical difficulties have hindered the development of working civilian fusion technology, though research continues to this day around the world. == Nuclear Weapons == The [[nuclear weapon design|design of a nuclear weapon]] is more complicated than it might seem; it is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. The construction of a nuclear weapon is also more difficult than it might seem, as no naturally occurring substance is sufficiently unstable for this process to occur. One [[isotope]] of uranium, namely uranium-235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium-238. Thus a complicated and difficult process of [[isotope separation]] must be performed to obtain uranium-235. Alternatively, the element [[plutonium]] possesses an isotope that is sufficiently unstable for this process to be usable. Plutonium does not occur naturally, so it must be manufactured in a [[nuclear reactor]]. Ultimately, [[the Manhattan Project]] manufactured nuclear weapons based on each of these. The first atomic bomb was detonated in a test code-named "[[Trinity test|Trinity]]", near [[Alamogordo]] on July 16, 1945. After much debate on the morality of using such a horrifying weapon, two bombs were dropped on the Japanese cities [[Hiroshima]] and [[Nagasaki, Nagasaki|Nagasaki]], and the Japanese surrender followed shortly. Several nations began nuclear weapons programs, developing ever more destructive bombs in an [[arms race]] to obtain what many called a [[nuclear deterrent]]. Nuclear weapons are the most destructive weapons known - the archetypal weapons of mass destruction. Throughout the [[Cold War]], the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. Generations of people grew up under the shadow of nuclear devastation. However, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source. == Nuclear Power == {{main|Nuclear power}} Commercial nuclear power began in the early 1950s in the [[US]], [[UK]], and [[Soviet Union]]. The first commercial reactors were heavily based on either research reactors or military reactors. The first commercial nuclear reactor to go online in the US was the [[Shippingport Atomic Power Station]] in [[Western Pennsylvania]]. Some countries have banned all forms of nuclear power.{{Fact|date=April 2008}} == Types of nuclear reaction == {{Cleanup-section|date=August 2007}} Most natural nuclear reactions fall under the heading of [[radioactive decay]], where a nucleus is unstable and decays after a random interval. The most common processes by which this can occur are [[alpha decay]], [[beta decay]], and [[gamma decay]]. Under suitable circumstances, a large unstable nucleus can break into two smaller nuclei, undergoing [[nuclear fission]]. If these neutrons are captured by a suitable nucleus, they can trigger fission as well, leading to a [[chain reaction]]. A mass of radioactive material large enough (and in a suitable configuration) is called a [[Critical mass (nuclear)|critical mass]]. When a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. If there are enough immediate decays to carry on the chain reaction, the mass is said to be [[prompt critical]], and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. However, if the mass is critical only when the delayed neutrons are included, the reaction can be controlled, for example by the introduction or removal of [[neutron absorber]]s. This is what allows [[nuclear reactor]]s to be built. Fast neutrons are not easily captured by nuclei; they must be slowed ([[slow neutron]]s), generally by collision with the nuclei of a [[neutron moderator]], before they can be easily captured. If nuclei are forced to collide, they can undergo [[nuclear fusion]]. This process may release or absorb energy. When the resulting nucleus is lighter than that of [[iron]], energy is normally released; when the nucleus is heavier than that of iron, energy is generally absorbed. This process of fusion occurs in stars, and results in the formation, in [[stellar nucleosynthesis]], of the light elements, from lithium to calcium, as well as some formation of the heavy elements, beyond Iron and Nickel, which cannot be created by nuclear fusion, via neutron capture - the [[S-process]]. The remaining abundance of heavy elements - from Nickel to Uranium and beyond - is due to [[supernova nucleosynthesis]], the [[R-process]]. Of course, these natural processes of astrophysics are not examples of nuclear ''technology''. Because of the very strong repulsion of nuclei, fusion is difficult to achieve in a controlled fashion. [[Hydrogen bomb]]s obtain their enormous destructive power from fusion, but obtaining controlled [[fusion power]] has so far proved elusive. Controlled fusion can be achieved in [[particle accelerator]]s; this is how many [[synthetic element]]s were produced. The [[Farnsworth-Hirsch Fusor]] is a device which can produce controlled fusion (and which can be built as a high-school science project), albeit at a net energy loss. It is sold commercially as a neutron source. The vast majority of everyday phenomena do not involve nuclear reactions. Most everyday phenomena only involve [[gravity]] and [[electromagnetism]]. Of the [[fundamental forces]] of nature, they are not the strongest, but the other two, the [[strong nuclear force]] and the [[weak nuclear force]] are essentially short-range forces so they do not play a role outside the atomic nucleus. Atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other, so in ordinary circumstances they cannot meet. == Nuclear Accidents == === Three Mile island Incident (1979) === The [[Three Mile Island incident]], which ironically occurred two weeks after the release of the disaster film ''[[The China Syndrome]]'' greatly impacted the public's perception of nuclear power. Many [[human factors]] engineering improvements were made to American power plants in the wake of Three Mile Island's partial meltdown.<ref>[http://www.alwaysimproving.com/training/Library/Documents/humanerformancetechnologyaccidentTMI.htm Human Performance Technology and the Accident at Three Mile Island]</ref> === Chernobyl Accident (1986) === The [[Chernobyl accident]] in [[1986]] further alarmed the public about nuclear power. While design differences between the [[RBMK]] reactor used at Chernobyl and most western reactors virtually eliminate the possibility of such an accident occurring outside of the former Soviet Union, it is only recently that the general public in the United States has started to embrace nuclear energy. == Examples of Nuclear Technology == ===Nuclear Power=== {{See|Nuclear Power}} Nuclear power is a type of nuclear technology involving the controlled use of nuclear fission to release energy for work including propulsion, heat, and the generation of electricity. Nuclear energy is produced by a controlled nuclear chain reaction which creates heat—and which is used to boil water, produce steam, and drive a steam turbine. The turbine can be used for mechanical work and also to generate electricity. Currently nuclear power is used to propel [[aircraft carrier]]s, [[icebreaker]]s and [[submarine]]s; and provides approximately 15.7% of the world's electricity (in 2004). The risk of radiation and cost have prohibited use of nuclear power in transport ships.<ref>[http://www.uic.com.au/nip32.htm Nuclear-powered Ships]</ref> ===Medical Applications=== '''Imaging''' - medical and dental x-ray imagers use of Cobalt-60 or other x-ray sources. [[Technetium-99m]] is used, attached to organic molecules, as radioactive tracer in the human body, before being excreted by the kidneys. Positron emitting nulceotides are used for high resolution, short time span imaging in applications known as [[Positron emission tomography]]. ===Industrial applications=== '''Oil and Gas Exploration'''- Nuclear [[well logging]] is used to help predict the commercial viability of new or existing wells. The technology involves the use of a neutron or gamma-ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography.[http://hps.org/publicinformation/radterms/radfact154.html] '''Road Construction''' - Nuclear moisture/density gauges are used to determine the density of soils, asphalt, and concrete. Typically a Cesium-137 source is used. ===Commercial applications=== An ionization [[smoke detector]] includes a tiny mass of radioactive [[americium]]-241, which is a source of [[alpha radiation]]. [[Tritium]] is used with [[phosphor]] in rifle sights to increase nighttime firing accuracy. Luminescent exit signs use the same technology.<ref>[http://www.physics.isu.edu/radinf/tritium.htm Tritium Information]</ref> ===Food Processing and Agriculture=== [[Image:RADURAcx.JPG|thumb|150px|right|The [[Radura]] logo, used to show a food has been treated with ionizing radiation.]] Food irradiation<ref name="FI">anon., Food Irradiation - A technique for preserving and improving the safety of food, WHO, Geneva, 1991</ref> is the process of exposing food to [[ionizing radiation]] in order to destroy [[microorganism]]s, [[bacteria]], [[virus]]es, or [[insect]]s that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration. [[Irradiation]] is a more general term of deliberate exposure of materials to radiation to achieve a technical goal (in this context 'ionizing radiation' is implied). As such it is also used on non-food items, such as medical hardware, plastics, tubes for gas-pipelines, hoses for floor-heating, shrink-foils for food packaging, automobile parts, wires and cables (isolation), tires, and even gemstones. Compared to the amount of food irradiated, the volume of those every-day applications is huge but not noticed by the consumer. The genuine effect of processing food by ionizing radiation relates to damages to the [[DNA]], the basic genetic information for life. Microorganisms can no longer proliferate and continue their malignant or pathogen activities. Spoilage causing micro-organisms cannot continue their activities. Insects do not survive or become incapable of proliferation. Plants cannot continue the natural ripening or aging process. All these effects are beneficial to the consumer and the food industry, likewise.<ref name="FI"/> It should be noted that the amount of energy imparted for effective food irradiation is low compared to cooking the same; even at a typical dose of 10 kGy most food, which is (with regard to warming) physically equivalent to water, would warm by only about 2.5 °C. The speciality of processing food by ionizing radiation is the fact, that the energy density per atomic transition is very high, it can cleave molecules and induce ionization (hence the name) which cannot be achieved by mere heating. This is the reason for new beneficial effects, however at the same time, for new concerns. The treatment of solid food by ionizing radiation can provide an effect similar to heat pasteurization of liquids, such as milk. However, the use of the term, cold pasteurization, to describe irradiated foods is controversial, because pasteurization and irradiation are fundamentally different processes, although the intended end results can in some cases be similar. Food irradiation is currently permitted by over 40 countries and volumes are estimated to exceed 500&thinsp;000 metric tons annually world wide. <ref>[http://nucleus.iaea.org/NUCLEUS/nucleus/Content/Applications/FICdb/FoodIrradiationClearances.jsp?module=cif NUCLEUS - Food Irradiation Clearances]</ref> <ref>Food irradiation, Position of ADA, J Am Diet Assoc. 2000;100:246-253. http://www.mindfully.org/Food/Irradiation-Position-ADA.htm retrieved 2007-11-15</ref> <ref name="IMRP2006">C.M. Deeley, M. Gao, R. Hunter, D.A.E. Ehlermann, The development of food irradiation in the Asia Pacific, the Americas and Europe; tutorial presented to the International Meeting on Radiation Processing, Kuala Lumpur, 2006. http://www.doubleia.org/index.php?sectionid=43&parentid=13&contentid=494 last visited 2007-11-16</ref> ==References== {{reflist}} == See also == * [http://www.nei.org/howitworks Nuclear Energy Institute – Beneficial Uses of Radiation] * [http://www.ans.org/pubs/journals/nt/ Nuclear Technology] {{Technology}} {{Nuclear technology}} [[category:Nuclear technology|!]] [[ar:تكنولوجيا نووية]] [[bn:নিউক্লিয় প্রযুক্তি]] [[de:Kerntechnik]] [[es:Tecnología nuclear]] [[fa:فن‌آوری هسته‌ای]] [[he:טכנולוגיה גרעינית]] [[sv:Kärnteknik]]