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100-527: It was modeled on the Canadian Chalk River National Research X-perimental (NRX) reactor. The 40 MW reactor used natural uranium fuel, while using heavy water as a moderator . It is a tank reactor type with a core size of 3.14 m (H) × 2.67 m (D). It first went critical July 10, 1960. The reactor was not under IAEA safeguards (which did not exist when the reactor was sold), although Canada stipulated, and

200-551: A World War II cooperative effort between Britain , the United States , and Canada , NRX was a multipurpose research reactor used to develop new isotopes, test materials and fuels, and produce neutron radiation beams, that became an indispensable tool in the blossoming field of condensed matter physics . The nuclear physics design of NRX emerged from the Montreal Laboratory of Canada's National Research Council , which

300-545: 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

400-441: 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

500-421: 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

600-476: A further power increase. About 14 seconds later valves were manually opened to drain the heavy water moderator from the calandria. As this took some time to become effective, power increased for 5 more seconds, peaked at an estimated 100 MW, then went down as the moderator level decreased and was at zero 25 seconds later. The whole accident, from low to high to zero power took about 108 seconds. Meanwhile, some fuel elements melted and were pierced in several places;

700-524: 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

800-472: 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,

900-650: A hexagonal lattice, 14,000 litres (3,100 imp gal; 3,700 US gal) of heavy water and helium gas to displace air and prevent corrosion . The level of water in the reactor could be adjusted to help set the power level. Sitting in the vertical tubes and surrounded by air were fuel elements or experimental items. This design was a forerunner of the CANDU reactors. The fuel elements contained fuel rods 3.1 metres (10 ft) long, 31 millimetres (1.2 in) in diameter and weighing 55 kilograms (121 lb), containing uranium fuel and sheathed in aluminium. Surrounding

1000-496: A life of twenty more years, India had declared that this reactor would be shut down by 2010 in accordance with the Indo-US nuclear accord reached between Indian Prime Minister Manmohan Singh and US President George W. Bush . The reactor was shut down on 31 December 2010. 19°00′28″N 72°55′07″E  /  19.00778°N 72.91861°E  / 19.00778; 72.91861 NRX NRX ( National Research Experimental )

1100-410: 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

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1200-434: 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

1300-459: 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

1400-427: 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

1500-516: 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

1600-591: 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

1700-441: 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,

1800-430: 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

1900-478: 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

2000-445: 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,

2100-463: 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

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2200-449: 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

2300-466: A year. CIRUS was shut down in September 1997 for refurbishment and was scheduled to resume operation in 2003. The reactor was brought back into operation two years late in 2005. During refurbishing, a low-temperature vacuum evaporation-based desalination unit was also coupled to the reactor to serve as demonstration of using waste heat from a research reactor for sea desalination. Even if the reactor has

2400-464: 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;

2500-403: 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

2600-434: Is a chemical element ; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert , monatomic gas and 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

2700-407: 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

2800-570: Is commonly used with no relation to the Chalk River plant. On December 12, 1952, the NRX reactor suffered a partial meltdown due to operator error and mechanical problems in the shut-off systems. For test purposes, some of the fuel channels had been disconnected from high-pressure water cooling and were connected by hoses to a temporary cooling system; one low-power channel was cooled only by airflow. During tests at low power, with low coolant flux through

2900-399: 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

3000-447: 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

3100-413: 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

CIRUS reactor - Misplaced Pages Continue

3200-516: Is often jointly credited with detecting 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

3300-527: 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 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

3400-474: 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

3500-520: 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

3600-466: 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

3700-416: 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

3800-402: 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

3900-506: 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

4000-624: 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

4100-413: 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

CIRUS reactor - Misplaced Pages Continue

4200-445: The safeguard bank while the other eight were controlled in an automatic sequence. Two pushbuttons on the main panel in the control room activated magnets to seal the rods to the pneumatic system, and the pushbutton to cause the pneumatic insertion of the rods into the core was located a few feet away. NRX was for a time the world's most powerful research reactor , vaulting Canada into the forefront of physics research. Emerging from

4300-616: 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

4400-567: The 1952 accident advanced the field of reactor safety significantly, and the concepts it highlighted (diversity and independence of safety systems, guaranteed shutdown capability, efficiency of man-machine interface ) became fundamentals of reactor design. The incident was the world's first severe nuclear reactor accident. 46°03′06″N 77°21′49″W  /  46.05167°N 77.36361°W  / 46.05167; -77.36361 Helium Helium (from Greek : ἥλιος , romanized :  helios , lit.   'sun')

4500-462: 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

4600-460: 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

4700-411: The U.S. supply contract for the heavy water explicitly specified, that it only be used for peaceful purposes. Nonetheless, CIRUS produced some of India's initial weapons-grade plutonium stockpile, as well as the plutonium for India's 1974 Pokhran-I (Codename Smiling Buddha ) nuclear test, the country's first nuclear test. At a capacity factor of 50–80%, CIRUS can produce 6.6–10.5 kg of plutonium

4800-605: 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

4900-440: 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

5000-412: 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

5100-406: The core, the supervisor noticed several control rods being pulled from the core; an operator in the basement had incorrectly opened pneumatic valves. The wrongly-opened valves were immediately closed, but some of the control rods did not reenter the core and stuck in almost withdrawn positions, but still low enough for their status lights to indicate them as lowered. Due to a miscommunication between

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5200-534: The early days of cancer radiation therapy , the NRX reactor was the world's only source of the isotope cobalt-60 , first used to bombard tumours in 1951. In 1994 Dr. Bertram Brockhouse shared the Nobel Prize in Physics for his work in the 1950s at NRX, which advanced the detection and analysis techniques used in the field of neutron scattering for condensed matter research. The CIRUS reactor , based on this design,

5300-446: 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)

5400-505: 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

5500-517: 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

5600-451: 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

5700-643: The fuel decay heat , the water cooling system was kept operating, leaking contaminated coolant to the reactor basement. About 10 kilocuries (400  TBq ) of radioactive materials, contained in about 4,500 cubic metres (1,200,000 US gal) of water, collected in the basement of the reactor building during the next few days. Clean-up of the reactor building required several months of work, assisted by 150 US Navy personnel after Admiral Rickover requested permission to send US nuclear submarine personnel to learn about cleaning up nuclear contamination. The US contingent included future US president Jimmy Carter , at

5800-492: The fuel element was an aluminium coolant tube with up to 250 litres per second (3,300 imp gal/min) of cooling water from the Ottawa River flowing through it. Between the coolant sheath and the calandria an air flow of 8 kilograms per second (1,100 lb/min) was maintained. Twelve of the vertical tubes contained control rods made of boron carbide powder inside steel tubes. These could be raised and lowered to control

5900-420: 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

6000-399: The helium cover gas leaked and air was aspirated inside. Hydrogen and other gases evolved by radiation-induced dissociation of cooling water, and 3–4 minutes later oxyhydrogen exploded in the calandria. During the incident, some gaseous fission products were vented to the atmosphere, and heavy water in the calandria was contaminated with the cooling water and the fission products. To remove

6100-567: 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

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6200-400: 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

6300-541: The high energy neutrons causing further fission reactions. Second, control rods absorb neutrons and adjust the power level or shut down the reactor in the course of normal operation. Either inserting the control rods or removing the heavy water moderator can stop the reaction. The NRX reactor incorporated a calandria, a sealed vertical aluminium cylindrical vessel with a diameter of 8 metres (26 ft) and height of 3 metres (9.8 ft). The core vessel held about 175 six-centimetre-diameter (2.4 in) vertical tubes in

6400-429: 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

6500-427: 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

6600-497: 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

6700-476: The number of free neutrons it generated. When a nuclear reactor such as NRX is operating, its nuclear chain reaction generates many free neutrons. In the late 1940s, NRX was the most intense neutron source in the world. NRX experienced one of the world's first major reactor accidents on 12 December 1952. The reactor began operation on 22 July 1947 under the National Research Council of Canada , and

6800-467: 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

6900-475: 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:

7000-402: 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

7100-472: 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

7200-420: 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

7300-510: 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

7400-421: The reaction, with any seven inserted being enough to absorb sufficient neutrons that no chain reaction could happen. The rods were held up by electromagnets , so that a power failure would cause them to fall into the tubes and terminate the reaction. A pneumatic system could use air pressure from above to quickly force them into the reactor core or from below to slowly raise them from it. Four of these were called

7500-412: The reactor. Three of the safeguard control rods, however, were not inserted into the core and the fourth took an abnormally long time, about 90 seconds, to insert, while the power kept rising. After just 10 seconds the core reached 17 MW(thermal) . The cooling water boiled in some tubes connected to the temporary cooling system, and some of them ruptured; the positive void coefficient of the reactor led to

7600-601: 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

7700-422: 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

7800-547: 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

7900-458: 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

8000-401: The supervisor and the control room operator, wrong buttons were pressed when the supervisor asked to lower the control rods into the core. Instead of sealing the withdrawn control rods to the pneumatic system, the safeguard bank of four control rods was accidentally withdrawn from the core. The operator noticed that the power level was exponentially increasing, doubling each 2 seconds, and tripped

8100-486: The time a lieutenant in the US nuclear submarine program who was in charge of 12 men. The NRX reactor core and calandria, damaged beyond repair, were removed and buried, and an improved replacement was installed; the refurbished reactor started operating 14 months and 5 days after the accident. The clean up was primarily performed by 850 Atomic Energy of Canada staff, assisted by about 170 Canadian and 150 U.S. military personnel, and 20 contractors. The lessons learned in

8200-450: 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)

8300-461: The universe is helium-4, the vast majority of which was formed during 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

8400-669: 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

8500-499: Was a heavy-water-moderated , light-water-cooled, nuclear research reactor at the Canadian Chalk River Laboratories , which came into operation in 1947 at a design power rating of 10 MW (thermal), increasing to 42 MW by 1954. At the time of its construction, it was Canada's most expensive science facility and the world's most powerful nuclear research reactor. NRX was remarkable both in terms of its heat output and

8600-520: 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

8700-409: 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

8800-501: Was built in India. It was ultimately used to produce plutonium for India's Operation Smiling Buddha nuclear test . It is claimed that the term "crud" originally stood for "Chalk River Unidentified Deposit", used to describe the radioactive scaling that builds up on internal reactor components, first observed in the NRX facility. Crud has since become common parlance for "Corrosion Related Unidentified Deposit" and similar expressions and

8900-553: 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

9000-421: Was established at the University of Montreal during WWII to engage a team of Canadian, British, and other European scientists in top-secret heavy-water reactor research. When the decision was made to build the NRX at what is now known as Chalk River Laboratories , the detailed engineering design was contracted to Canada's Defence Industries Limited (DIL), who subcontracted construction to Fraser Brace Ltd. In

9100-500: 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

9200-488: 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

9300-690: 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 ,

9400-582: 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

9500-472: Was not expected to be very long, in 1948 planning started for construction of a successor facility, the National Research Universal reactor , which started self-sustained operation (or "went critical") in 1957. A heavy water moderated reactor is governed by two main processes. First, the water slows down ( moderates ) the neutrons which are produced by nuclear fission, increasing the chances of

9600-453: 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

9700-406: 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

9800-522: 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

9900-507: 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,

10000-479: Was taken over by Atomic Energy of Canada Limited (AECL) shortly before the 1952 accident. The accident was cleaned up and the reactor restarted within two years. NRX operated for 45 years, then shut down permanently on 30 March 1993. Decommissioning is underway at the Chalk River Laboratories site. NRX was the successor to Canada's first reactor, ZEEP . Because the operating life of a research reactor

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