Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed.
116-457: ATW may refer to: Technology [ edit ] Accelerator transmutation of waste , a way of processing radioactive waste Atari Transputer Workstation , a computer produced in 1980s Asynchronous TimeWarp , a technique used in virtual reality headsets Entertainment [ edit ] All Too Well , a song written by American singer-songwriter Taylor Swift and Liz Rose and performed by
232-545: A nuclear halo . Table of thermal and physical properties of helium gas at atmospheric pressure: Helium has a valence of zero and is chemically unreactive under all normal conditions. It is an electrical insulator unless ionized . As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential . Helium can form unstable compounds , known as excimers , with tungsten, iodine, fluorine, sulfur, and phosphorus when it
348-441: A superfluid phase, but only at much lower temperatures; as a result, less is known about the properties of the isotope. Helium II is a superfluid, a quantum mechanical state of matter with strange properties. For example, when it flows through capillaries as thin as 10 to 100 nm it has no measurable viscosity . However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium
464-456: A cloud of hydrogen and helium containing heavier elements in dust grains formed previously by a large number of such stars. These grains contained the heavier elements formed by transmutation earlier in the history of the universe. All of these natural processes of transmutation in stars are continuing today, in our own galaxy and in others. Stars fuse hydrogen and helium into heavier and heavier elements (up to iron), producing energy. For example,
580-421: A few millikelvins. It is possible to produce exotic helium isotopes , which rapidly decay into other substances. The shortest-lived heavy helium isotope is the unbound helium-10 with a half-life of 2.6(4) × 10 s . Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 and helium-8 are created in certain nuclear reactions . Helium-6 and helium-8 are known to exhibit
696-524: A gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is. This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K), which is only one-fourth the value expected from classical physics . Quantum mechanics is needed to explain this property and thus both states of liquid helium (helium I and helium II) are called quantum fluids , meaning they display atomic properties on
812-472: A helium-oxygen bond could be stable. Two new molecular species, predicted using theory, CsFHeO and N(CH 3 ) 4 FHeO, are derivatives of a metastable FHeO anion first theorized in 2005 by a group from Taiwan. Helium atoms have been inserted into the hollow carbon cage molecules (the fullerenes ) by heating under high pressure. The endohedral fullerene molecules formed are stable at high temperatures. When chemical derivatives of these fullerenes are formed,
928-444: A large amount of energy. The released neutrons then cause fission of other uranium atoms, until all of the available uranium is exhausted. This is called a chain reaction . Artificial nuclear transmutation has been considered as a possible mechanism for reducing the volume and hazard of radioactive waste . The term transmutation dates back to alchemy . Alchemists pursued the philosopher's stone , capable of chrysopoeia –
1044-410: A lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator . Equal mixtures of liquid He and He below 0.8 K separate into two immiscible phases due to their dissimilarity (they follow different quantum statistics : helium-4 atoms are bosons while helium-3 atoms are fermions ). Dilution refrigerators use this immiscibility to achieve temperatures of
1160-434: A macroscopic scale. This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion ( thermal energy ) from masking the atomic properties. Liquid helium below its lambda point (called helium II ) exhibits very unusual characteristics. Due to its high thermal conductivity , when it boils, it does not bubble but rather evaporates directly from its surface. Helium-3 also has
1276-465: A minuscule amount of gold from bismuth, at a net energy loss. The Big Bang is thought to be the origin of the hydrogen (including all deuterium ) and helium in the universe. Hydrogen and helium together account for 98% of the mass of ordinary matter in the universe, while the other 2% makes up everything else. The Big Bang also produced small amounts of lithium , beryllium and perhaps boron . More lithium, beryllium and boron were produced later, in
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#17327753530101392-489: A natural nuclear reaction, cosmic ray spallation . Stellar nucleosynthesis is responsible for all of the other elements occurring naturally in the universe as stable isotopes and primordial nuclide , from carbon to uranium . These occurred after the Big Bang, during star formation. Some lighter elements from carbon to iron were formed in stars and released into space by asymptotic giant branch (AGB) stars. These are
1508-459: A negative Joule–Thomson coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule–Thomson inversion temperature (of about 32 to 50 K at 1 atmosphere) does it cool upon free expansion. Once precooled below this temperature, helium can be liquefied through expansion cooling. Most extraterrestrial helium is plasma in stars, with properties quite different from those of atomic helium. In
1624-427: A new form of hydrogen with half-integer transition levels. In 1912, Alfred Fowler managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin. Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He . Fowler
1740-516: A phenomenon now called superfluidity . This phenomenon is related to Bose–Einstein condensation . In 1972, the same phenomenon was observed in helium-3 , but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff , David M. Lee , and Robert C. Richardson . The phenomenon in helium-3 is thought to be related to pairing of helium-3 fermions to make bosons , in analogy to Cooper pairs of electrons producing superconductivity . In 1961, Vignos and Fairbank reported
1856-595: A plasma, helium's electrons are not bound to its nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind together with ionized hydrogen, the particles interact with the Earth's magnetosphere , giving rise to Birkeland currents and the aurora . Helium liquifies when cooled below 4.2 K at atmospheric pressure. Unlike any other element, however, helium remains liquid down to
1972-441: A pressurizing and purge gas, as a protective atmosphere for arc welding , and in processes such as growing crystals to make silicon wafers —account for half of the gas produced. A small but well-known use is as a lifting gas in balloons and airships . As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice . In scientific research,
2088-430: A rate three times that of air and around 65% that of hydrogen. Helium is the least water- soluble monatomic gas, and one of the least water-soluble of any gas ( CF 4 , SF 6 , and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10 , respectively, versus helium's 0.70797 x 2 /10 ), and helium's index of refraction is closer to unity than that of any other gas. Helium has
2204-478: A reconsideration of the Pickering–Fowler series as central evidence in support of his model of the atom . This series is named for Edward Charles Pickering , who in 1896 published observations of previously unknown lines in the spectrum of the star ζ Puppis (these are now known to occur with Wolf–Rayet and other hot stars). Pickering attributed the observation (lines at 4551, 5411, and 10123 Å ) to
2320-408: A relatively short half life to a stable isotope of ruthenium , a precious metal , there might also be some economic incentive to transmutation, if costs can be brought low enough. Of the remaining five long-lived fission products, selenium-79 , tin-126 and palladium-107 are produced only in small quantities (at least in today's thermal neutron , U -burning light water reactors ) and
2436-486: A research fellow working under Rutherford, with the transmutation of nitrogen into oxygen , using alpha particles directed at nitrogen N + α → O + p. Rutherford had shown in 1919 that a proton (he called it a hydrogen atom) was emitted from alpha bombardment experiments but he had no information about the residual nucleus. Blackett's 1921–1924 experiments provided the first experimental evidence of an artificial nuclear transmutation reaction. Blackett correctly identified
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#17327753530102552-445: A result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity,
2668-405: A scale of decades to ~305 years ( tin-121m is insignificant because of the low yield), and are not easily transmuted because they have low neutron absorption cross sections . Instead, they should simply be stored until they decay. Given that this length of storage is necessary, the fission products with shorter half-lives can also be stored until they decay. The next longer-lived fission product
2784-399: A smaller amount of this element at the end of cycle. During the cycle, plutonium can be burnt in a power reactor, generating electricity. This process is not only interesting from a power generation standpoint, but also due to its capability of consuming the surplus weapons grade plutonium from the weapons program and plutonium resulting of reprocessing used nuclear fuel. Mixed oxide fuel
2900-593: A spectrum of radioactive and nonradioactive fission products . Ceramic targets containing actinides can be bombarded with neutrons to induce transmutation reactions to remove the most difficult long-lived species. These can consist of actinide-containing solid solutions such as (Am,Zr)N , (Am,Y)N , (Zr,Cm)O 2 , (Zr,Cm,Am)O 2 , (Zr,Am,Y)O 2 or just actinide phases such as AmO 2 , NpO 2 , NpN , AmN mixed with some inert phases such as MgO , MgAl 2 O 4 , (Zr,Y)O 2 , TiN and ZrN . The role of non-radioactive inert phases
3016-463: A surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity . Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin . As
3132-449: A temperature of absolute zero . This is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. Pressures above about 25 atmospheres are required to freeze it. There are two liquid phases: Helium I is a conventional liquid, and Helium II, which occurs at a lower temperature, is a superfluid . Below its boiling point of 4.22 K (−268.93 °C; −452.07 °F) and above
3248-721: A theatre education organization Arriva Trains Wales , a former train operating company in the United Kingdom Atlantic and Western Railway , in North Carolina, United States Places [ edit ] Agua Tibia Wilderness , a protected area in California Appleton International Airport (IATA airport code: ATW), in Appleton, Wisconsin, United States Military [ edit ] Anti-Tank Weapon,
3364-414: A type of red giant that "puffs" off its outer atmosphere, containing some elements from carbon to nickel and iron. Nuclides with mass number greater than 64 are predominantly produced by neutron capture processes—the s -process and r -process –in supernova explosions and neutron star mergers . The Solar System is thought to have condensed approximately 4.6 billion years before the present, from
3480-650: A weapon designed to destroy tanks . Other [ edit ] Around the World Atsugewi language (ISO 639-3: atw), a language of North America Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title ATW . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=ATW&oldid=1212328849 " Category : Disambiguation pages Hidden categories: Short description
3596-464: A γ phase, which is body-centered cubic (bcc). There are nine known isotopes of helium of which two, helium-3 and helium-4 , are stable . In the Earth's atmosphere, one atom is He for every million that are He . Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements;
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3712-403: Is 0.187 ± 0.009 g/cm . At higher temperatures, helium will solidify with sufficient pressure. At room temperature, this requires about 114,000 atm. Helium-4 and helium-3 both form several crystalline solid phases, all requiring at least 25 bar. They both form an α phase, which has a hexagonal close-packed (hcp) crystal structure, a β phase, which is face-centered cubic (fcc), and
3828-565: Is samarium-151 , which has a half-life of 90 years, and is such a good neutron absorber that most of it is transmuted while the nuclear fuel is still being used; however, effectively transmuting the remaining Sm in nuclear waste would require separation from other isotopes of samarium . Given the smaller quantities and its low-energy radioactivity, Sm is less dangerous than Sr and Cs and can also be left to decay for ~970 years. Finally, there are seven long-lived fission products . They have much longer half-lives in
3944-407: Is a non-renewable resource because once released into the atmosphere, it promptly escapes into space . Its supply is thought to be rapidly diminishing. However, some studies suggest that helium produced deep in the Earth by radioactive decay can collect in natural gas reserves in larger-than-expected quantities, in some cases having been released by volcanic activity. The first evidence of helium
4060-399: Is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. If the interior of the container is heated, the superfluid helium changes to non-superfluid helium. In order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases
4176-447: Is created by the natural radioactive decay of heavy radioactive elements ( thorium and uranium , although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei . This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation . Terrestrial helium
4292-402: Is different from Wikidata All article disambiguation pages All disambiguation pages Accelerator transmutation of waste A transmutation can be achieved either by nuclear reactions (in which an outside particle reacts with a nucleus) or by radioactive decay , where no outside cause is needed. Natural transmutation by stellar nucleosynthesis in the past created most of
4408-456: Is mainly to provide stable mechanical behaviour to the target under neutron irradiation. There are issues with this P&T (partitioning and transmutation) strategy however: The new study led by Satoshi Chiba at Tokyo Tech (called "Method to Reduce Long-lived Fission Products by Nuclear Transmutations with Fast Spectrum Reactors" ) shows that effective transmutation of long-lived fission products can be achieved in fast spectrum reactors without
4524-413: Is no exception. Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons. Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps. Such models show that each electron in helium partly screens the nucleus from
4640-441: Is one of these. Its blend of oxides of plutonium and uranium constitutes an alternative to the low enriched uranium fuel predominantly used in light water reactors. Since uranium is present in mixed oxide, although plutonium will be burnt, second generation plutonium will be produced through the radiative capture of uranium-238 and the two subsequent beta minus decays. Fuels with plutonium and thorium are also an option. In these,
4756-479: Is produced in fusion reactions from hydrogen, though its estimated abundance in the universe is about 10 relative to helium-4. The unusual stability of the helium-4 nucleus is also important cosmologically : it explains the fact that in the first few minutes after the Big Bang , as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding
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4872-459: Is similar to this in both the Sun and Jupiter , because of the very high nuclear binding energy (per nucleon ) of helium-4 , with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay . The most common isotope of helium in the universe is helium-4, the vast majority of which was formed during
4988-520: Is subjected to a glow discharge , to electron bombardment, or reduced to plasma by other means. The molecular compounds HeNe, HgHe 10 , and WHe 2 , and the molecular ions He 2 , He 2 , HeH , and HeD have been created this way. HeH is also stable in its ground state but is extremely reactive—it is the strongest Brønsted acid known, and therefore can exist only in isolation, as it will protonate any molecule or counteranion it contacts. This technique has also produced
5104-466: Is the second least reactive noble gas after neon , and thus the second least reactive of all elements. It is chemically inert and monatomic in all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity , specific heat , and sound speed in the gas phase are all greater than any other gas except hydrogen . For these reasons and the small size of helium monatomic molecules, helium diffuses through solids at
5220-416: Is thus energetically extremely stable for all these particles and has astrophysical implications. Namely, adding another particle – proton, neutron, or alpha particle – would consume rather than release energy; all systems with mass number 5, as well as beryllium-8 (comprising two alpha particles), are unbound. For example, the stability and low energy of the electron cloud state in helium accounts for
5336-402: The 2017 Qatar diplomatic crisis severely affected helium production there. 2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages. Nasdaq reported (2015) that for Air Products , an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints. In
5452-431: The Big Bang . Large amounts of new helium are created by nuclear fusion of hydrogen in stars . Helium was first detected as an unknown, yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet , Captain C. T. Haig, Norman R. Pogson , and Lieutenant John Herschel, and was subsequently confirmed by French astronomer Jules Janssen . Janssen is often jointly credited with detecting
5568-573: The Naval Aircraft Factory -built USS Shenandoah , flew in September 1923. Although the extraction process using low-temperature gas liquefaction was not developed in time to be significant during World War I, production continued. Helium was primarily used as a lifting gas in lighter-than-air craft. During World War II, the demand increased for helium for lifting gas and for shielded arc welding . The helium mass spectrometer
5684-624: The beta decay of tritium . Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle . He is much more abundant in stars as a product of nuclear fusion. Thus in the interstellar medium , the proportion of He to He is about 100 times higher than on Earth. Extraplanetary material, such as lunar and asteroid regolith , have trace amounts of helium-3 from being bombarded by solar winds . The Moon 's surface contains helium-3 at concentrations on
5800-413: The lambda point of 2.1768 K (−270.9732 °C; −455.7518 °F), the isotope helium-4 exists in a normal colorless liquid state, called helium I . Like other cryogenic liquids, helium I boils when it is heated and contracts when its temperature is lowered. Below the lambda point, however, helium does not boil, and it expands as the temperature is lowered further. Helium I has
5916-626: The uranium ore cleveite , which is now not regarded as a separate mineral species, but as a variety of uraninite . In 1903, large reserves of helium were found in natural gas fields in parts of the United States, by far the largest supplier of the gas today. Liquid helium is used in cryogenics (its largest single use, consuming about a quarter of production), and in the cooling of superconducting magnets , with its main commercial application in MRI scanners. Helium's other industrial uses—as
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#17327753530106032-411: The Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Helium-4, by contrast, comprises about 24% of the mass of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen. Helium
6148-465: The Interior to empty the reserve, with sales starting by 2005. Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available. For many years, the United States produced more than 90% of commercially usable helium in
6264-498: The Plutonium content of used MOX-fuel. The heavier elements could be transmuted in fast reactors , but probably more effectively in a subcritical reactor which is sometimes known as an energy amplifier and which was devised by Carlo Rubbia . Fusion neutron sources have also been proposed as well suited. There are several fuels that can incorporate plutonium in their initial composition at their beginning of cycle and have
6380-619: The United States in 1965 was more than eight times the peak wartime consumption. After the Helium Acts Amendments of 1960 (Public Law 86–777), the U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a 425-mile (684 km) pipeline from Bushton, Kansas , to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture
6496-403: The absence of uranium in the fuel, there is no second generation plutonium produced, and the amount of plutonium burnt will be higher than in mixed oxide fuels. However, uranium-233, which is fissile, will be present in the used nuclear fuel. Weapons-grade and reactor-grade plutonium can be used in plutonium–thorium fuels, with weapons-grade plutonium being the one that shows a bigger reduction in
6612-440: The alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells . It was also formed in enormous quantities during Big Bang nucleosynthesis . Helium-3 is present on Earth only in trace amounts. Most of it has been present since Earth's formation, though some falls to Earth trapped in cosmic dust . Trace amounts are also produced by
6728-455: The amount of plutonium-239. Some radioactive fission products can be converted into shorter-lived radioisotopes by transmutation. Transmutation of all fission products with half-life greater than one year is studied in Grenoble, with varying results. Strontium-90 and caesium-137, with half-lives of about 30 years, are the largest radiation (including heat) emitters in used nuclear fuel on
6844-412: The behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity ) and to those looking at the phenomena, such as superconductivity , produced in matter near absolute zero . On Earth, it is relatively rare—5.2 ppm by volume in the atmosphere . Most terrestrial helium present today
6960-446: The element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements. In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions that involve either heavy-particle emission or fusion. Some stable helium-3 (two protons and one neutron)
7076-478: The element, along with Norman Lockyer . Janssen recorded the helium spectral line during the solar eclipse of 1868, while Lockyer observed it from Britain. However, only Lockyer proposed that the line was due to a new element, which he named after the Sun. The formal discovery of the element was made in 1895 by chemists Sir William Ramsay , Per Teodor Cleve , and Nils Abraham Langlet , who found helium emanating from
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#17327753530107192-515: The existence of a different phase of solid helium-4, designated the gamma-phase. It exists for a narrow range of pressure between 1.45 and 1.78 K. After an oil drilling operation in 1903 in Dexter, Kansas produced a gas geyser that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, with
7308-517: The existence of this new element. The ending "-ium" is unusual, as it normally applies only to metallic elements; probably Lockyer, being an astronomer, was unaware of the chemical conventions. In 1881, Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D 3 spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius . On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating
7424-451: The few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4. All heavier elements (including those necessary for rocky planets like
7540-436: The first in the noble gas group in the periodic table . Its boiling point is the lowest among all the elements , and it does not have a melting point at standard pressures. It is the second-lightest and second most abundant element in the observable universe , after hydrogen . It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance
7656-516: The former Access 31 , a former Perth television station with callsign ATW, now replaced by West TV Air Transport World , a magazine Ansem the Wise, a character from the Kingdom Hearts series American Travelways, a fictional airline in the 1986 film The Delta Force ATW (album) , an album by All Them Witches Organizations [ edit ] American Theatre Wing ,
7772-420: The heat. Helium II has no such valence band but nevertheless conducts heat well. The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound . Helium II also exhibits a creeping effect. When
7888-580: The heavier chemical elements in the known existing universe, and continues to take place to this day, creating the vast majority of the most common elements in the universe, including helium , oxygen and carbon . Most stars carry out transmutation through fusion reactions involving hydrogen and helium, while much larger stars are also capable of fusing heavier elements up to iron late in their evolution. Elements heavier than iron, such as gold or lead , are created through elemental transmutations that can naturally occur in supernovae . One goal of alchemy,
8004-567: The helium stays inside. If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy . Many fullerenes containing helium-3 have been reported. Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds. Under high pressures helium can form compounds with various other elements. Helium-nitrogen clathrate (He(N 2 ) 11 ) crystals have been grown at room temperature at pressures ca. 10 GPa in
8120-400: The help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% methane (a combustible percentage only with sufficient oxygen), 1% hydrogen , and 12% an unidentifiable gas. With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium. This showed that despite its overall rarity on Earth, helium
8236-594: The initial formation of the Solar System (such as potassium-40 , uranium and thorium), plus the radioactive decay of products of these nuclides (radium, radon, polonium, etc.). See decay chain . Transmutation of transuranium elements (i.e. actinides minus actinium to uranium ) such as the isotopes of plutonium (about 1wt% in the light water reactors ' used nuclear fuel or the minor actinides (MAs, i.e. neptunium , americium , and curium ), about 0.1wt% each in light water reactors' used nuclear fuel) has
8352-419: The last two should be relatively inert. The other two, zirconium-93 and caesium-135 , are produced in larger quantities, but also not highly mobile in the environment. They are also mixed with larger quantities of other isotopes of the same element. Zirconium is used as cladding in fuel rods due to being virtually "transparent" to neutrons, but a small amount of Zr is produced by neutron absorption from
8468-440: The lightest chemical elements could be explained by the process of nucleosynthesis in stars. The alchemical tradition sought to turn the "base metal", lead, into gold. As a nuclear transmutation, it requires far less energy to turn gold into lead; for example, this would occur via neutron capture and beta decay if gold were left in a nuclear reactor for a sufficiently long period of time. Glenn Seaborg succeeded in producing
8584-429: The lines to nitrogen . His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science. In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube , then creating a discharge in the tube, to study the spectrum of the new gas inside. In 1908, helium
8700-427: The mineral cleveite (a variety of uraninite with at least 10% rare-earth elements ) with mineral acids . Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas, liberated by sulfuric acid , he noticed a bright yellow line that matched the D 3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes . It
8816-438: The modern nuclear fission reaction discovered in 1938 by Otto Hahn , Lise Meitner and their assistant Fritz Strassmann in heavy elements. In 1941, Rubby Sherr , Kenneth Bainbridge and Herbert Lawrence Anderson reported the nuclear transmutation of mercury into gold . Later in the twentieth century the transmutation of elements within stars was elaborated, accounting for the relative abundance of heavier elements in
8932-431: The moment of realization, Soddy later recalled, he shouted out: "Rutherford, this is transmutation!" Rutherford snapped back, "For Christ's sake, Soddy, don't call it transmutation . They'll have our heads off as alchemists." Rutherford and Soddy were observing natural transmutation as a part of radioactive decay of the alpha decay type. The first artificial transmutation was accomplished in 1925 by Patrick Blackett ,
9048-614: The need for isotope separation. This can be achieved by adding a yttrium deuteride moderator. For instance, plutonium can be reprocessed into mixed oxide fuels and transmuted in standard reactors. However, this is limited by the accumulation of plutonium-240 in spent MOX fuel, which is neither particularly fertile (transmutation to fissile plutonium-241 does occur, but at lower rates than production of more plutonium-240 from neutron capture by plutonium-239 ) nor fissile with thermal neutrons. Even countries like France which practice nuclear reprocessing extensively, usually do not reuse
9164-497: The neutral molecule He 2 , which has a large number of band systems , and HgHe, which is apparently held together only by polarization forces. Van der Waals compounds of helium can also be formed with cryogenic helium gas and atoms of some other substance, such as LiHe and He 2 . Theoretically, other true compounds may be possible, such as helium fluorohydride (HHeF), which would be analogous to HArF , discovered in 2000. Calculations show that two new compounds containing
9280-425: The neutrons released in the fission of plutonium are captured by thorium-232 . After this radiative capture, thorium-232 becomes thorium-233, which undergoes two beta minus decays resulting in the production of the fissile isotope uranium-233 . The radiative capture cross section for thorium-232 is more than three times that of uranium-238, yielding a higher conversion to fissile fuel than that from uranium-238. Due to
9396-424: The notion of atoms (from the alchemical theory of corpuscles ) to explain various chemical processes. The disintegration of atoms is a distinct process involving much greater energies than could be achieved by alchemists. It was first consciously applied to modern physics by Frederick Soddy when he, along with Ernest Rutherford in 1901, discovered that radioactive thorium was converting itself into radium . At
9512-467: The nuclear structure of the elements. Such machines include particle accelerators and tokamak reactors. Conventional fission power reactors also cause artificial transmutation, not from the power of the machine, but by exposing elements to neutrons produced by fission from an artificially produced nuclear chain reaction . For instance, when a uranium atom is bombarded with slow neutrons, fission takes place. This releases, on average, three neutrons and
9628-415: The observed light curves of supernova stars such as SN 1987A show them blasting large amounts (comparable to the mass of Earth) of radioactive nickel and cobalt into space. However, little of this material reaches Earth. Most natural transmutation on the Earth today is mediated by cosmic rays (such as production of carbon-14 ) and by the radioactive decay of radioactive primordial nuclides left over from
9744-471: The order of 10 ppb , much higher than the approximately 5 ppt found in the Earth's atmosphere. A number of people, starting with Gerald Kulcinski in 1986, have proposed to explore the Moon, mine lunar regolith, and use the helium-3 for fusion . Liquid helium-4 can be cooled to about 1 K (−272.15 °C; −457.87 °F) using evaporative cooling in a 1-K pot . Similar cooling of helium-3, which has
9860-475: The other, so that the effective nuclear charge Z eff which each electron sees is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus. The nucleus of the helium-4 atom is identical with an alpha particle . High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud . This symmetry reflects similar underlying physics:
9976-402: The pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. This arrangement
10092-477: The perspective of quantum mechanics , helium is the second simplest atom to model, following the hydrogen atom . Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem ) and helium
10208-422: The potential to help solve some problems posed by the management of radioactive waste by reducing the proportion of long-lived isotopes it contains. (This does not rule out the need for a deep geological repository for high level radioactive waste .) When irradiated with fast neutrons in a nuclear reactor , these isotopes can undergo nuclear fission , destroying the original actinide isotope and producing
10324-664: The present occurs when certain radioactive elements present in nature spontaneously decay by a process that causes transmutation, such as alpha or beta decay . An example is the natural decay of potassium-40 to argon-40 , which forms most of the argon in the air. Also on Earth, natural transmutations from the different mechanisms of natural nuclear reactions occur, due to cosmic ray bombardment of elements (for example, to form carbon-14 ), and also occasionally from natural neutron bombardment (for example, see natural nuclear fission reactor ). Artificial transmutation may occur in machinery that has enough energy to cause changes in
10440-420: The pressure, causing liquid to fountain out of the container. The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of copper . This is because heat conduction occurs by an exceptional quantum mechanism. Most materials that conduct heat well have a valence band of free electrons which serve to transfer
10556-522: The prohibitive cost of the gas, German Zeppelins were forced to use hydrogen as lifting gas, which would gain infamy in the Hindenburg disaster . The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War . Helium use in
10672-613: The range 211,000 years to 15.7 million years. Two of them, technetium-99 and iodine-129 , are mobile enough in the environment to be potential dangers, are free ( Technetium has no known stable isotopes) or mostly free of mixture with stable isotopes of the same element, and have neutron cross sections that are small but adequate to support transmutation. Additionally, Tc can substitute for uranium-238 in supplying Doppler broadening for negative feedback for reactor stability. Most studies of proposed transmutation schemes have assumed Tc , I , and transuranium elements as
10788-418: The regular zircalloy without much ill effect. Whether Zr could be reused for new cladding material has not been subject of much study thus far. Helium Helium (from Greek : ἥλιος , romanized : helios , lit. 'sun') is a chemical element ; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert , monatomic gas and
10904-617: The reserve to continue to sell the gas. Other large reserves were in the Hugoton in Kansas , United States, and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma . New helium plants were scheduled to open in 2012 in Qatar , Russia, and the US state of Wyoming , but they were not expected to ease the shortage. In 2013, Qatar started up the world's largest helium unit, although
11020-422: The restoring force is the van der Waals force . These waves are known as third sound . Helium remains liquid down to absolute zero at atmospheric pressure, but it freezes at high pressure. Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) at about 25 bar (2.5 MPa) of pressure. It is often hard to distinguish solid from liquid helium since the refractive index of
11136-571: The second leading producer of helium. Through this time, both helium consumption and the costs of producing helium increased. From 2002 to 2007 helium prices doubled. As of 2012 , the United States National Helium Reserve accounted for 30 percent of the world's helium. The reserve was expected to run out of helium in 2018. Despite that, a proposed bill in the United States Senate would allow
11252-462: The solar spectrum, which he named the D 3 because it was near the known D 1 and D 2 Fraunhofer lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer named the element with the Greek word for the Sun, ἥλιος ( helios ). It is sometimes said that English chemist Edward Frankland was also involved in the naming, but this is unlikely as he doubted
11368-412: The targets for transmutation, with other fission products, activation products , and possibly reprocessed uranium remaining as waste. Technetium-99 is also produced as a waste product in nuclear medicine from Technetium-99m , a nuclear isomer that decays to its ground state which has no further use. Due to the decay product of Tc (the result of Tc capturing a neutron) decaying with
11484-481: The transformation of base metals into gold. While alchemists often understood chrysopoeia as a metaphor for a mystical or religious process, some practitioners adopted a literal interpretation and tried to make gold through physical experimentation. The impossibility of the metallic transmutation had been debated amongst alchemists, philosophers and scientists since the Middle Ages. Pseudo-alchemical transmutation
11600-440: The transmutation of base substances into gold, is now known to be impossible by chemical means but possible by physical means. As stars begin to fuse heavier elements, substantially less energy is released from each fusion reaction. This continues until it reaches iron which is produced by an endothermic reaction consuming energy. No heavier element can be produced in such conditions. One type of natural transmutation observable in
11716-450: The two phases are nearly the same. The solid has a sharp melting point and has a crystalline structure, but it is highly compressible ; applying pressure in a laboratory can decrease its volume by more than 30%. With a bulk modulus of about 27 MPa it is ~100 times more compressible than water. Solid helium has a density of 0.214 ± 0.006 g/cm at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa)
11832-406: The underlying integration process and the identity of the residual nucleus. In 1932, a fully artificial nuclear reaction and nuclear transmutation was achieved by Rutherford's colleagues John Cockcroft and Ernest Walton , who used artificially accelerated protons against lithium-7 to split the nucleus into two alpha particles. The feat was popularly known as "splitting the atom", although it was not
11948-512: The universe. Save for the first five elements, which were produced in the Big Bang and other cosmic ray processes, stellar nucleosynthesis accounted for the abundance of all elements heavier than boron . In their 1957 paper Synthesis of the Elements in Stars , William Alfred Fowler , Margaret Burbidge , Geoffrey Burbidge , and Fred Hoyle explained how the abundances of essentially all but
12064-683: The world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In the mid-1990s, a new plant in Arzew , Algeria, producing 17 million cubic metres (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year. In 2004–2006, additional plants in Ras Laffan , Qatar , and Skikda , Algeria were built. Algeria quickly became
12180-536: Was also vital in the atomic bomb Manhattan Project . The government of the United States set up the National Helium Reserve in 1925 at Amarillo, Texas , with the goal of supplying military airships in time of war and commercial airships in peacetime. Because of the Helium Act of 1925 , which banned the export of scarce helium on which the US then had a production monopoly, together with
12296-409: Was available to make elements 3, 4 and 5. It is barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon , carbon. However, due to the short lifetime of the intermediate beryllium-8, this process requires three helium nuclei striking each other nearly simultaneously (see triple-alpha process ). There was thus no time for significant carbon to be formed in
12412-570: Was concentrated in large quantities under the American Great Plains , available for extraction as a byproduct of natural gas . Following a suggestion by Sir Richard Threlfall , the United States Navy sponsored three small experimental helium plants during World War I. The goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. A total of 5,700 m (200,000 cu ft) of 92% helium
12528-500: Was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than 5 K (−268.15 °C; −450.67 °F). He tried to solidify it by further reducing the temperature but failed, because helium does not solidify at atmospheric pressure. Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm of helium in 1926 by applying additional external pressure. In 1913, Niels Bohr published his "trilogy" on atomic structure that included
12644-493: Was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala , Sweden, who collected enough of the gas to accurately determine its atomic weight . Helium was also isolated by American geochemist William Francis Hillebrand prior to Ramsay's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed
12760-695: Was initially skeptical but was ultimately convinced that Bohr was correct, and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium." Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory. In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero ,
12876-602: Was injected and stored in the Cliffside gas field until needed, at which time it was further purified. By 1995, a billion cubic meters of the gas had been collected and the reserve was US$ 1.4 billion in debt, prompting the Congress of the United States in 1996 to discontinue the reserve. The resulting Helium Privatization Act of 1996 (Public Law 104–273) directed the United States Department of
12992-457: Was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun . The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur , India. This line was initially assumed to be sodium . On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in
13108-406: Was observed. Existing theory explains this using the two-fluid model for helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state , which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid. In the fountain effect , a chamber
13224-471: Was outlawed and publicly mocked beginning in the fourteenth century. Alchemists like Michael Maier and Heinrich Khunrath wrote tracts exposing fraudulent claims of gold making. By the 1720s, there were no longer any respectable figures pursuing the physical transmutation of substances into gold. Antoine Lavoisier , in the 18th century, replaced the alchemical theory of elements with the modern theory of chemical elements, and John Dalton further developed
13340-522: Was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. Owing to the relatively tight binding of helium-4 nuclei, its production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and thus few neutrons were available to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy ) and thus, once helium had been formed, no energetic drive
13456-517: Was produced in the program even though less than a cubic meter of the gas had previously been obtained. Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's C-class blimp C-7, which flew its maiden voyage from Hampton Roads, Virginia , to Bolling Field in Washington, D.C., on December 1, 1921, nearly two years before the Navy's first rigid helium-filled airship,
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