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62-478: The reactor reached criticality on December 2, 1957, and aside from stoppages for three core changes, it remained in operation until October 1982. The first electrical power was produced on December 18, 1957 as engineers synchronized the plant with the distribution grid of Duquesne Light Company. The first core used at Shippingport originated from a cancelled nuclear-powered aircraft carrier and used highly enriched uranium (93% U-235) as "seed" fuel surrounded by

124-473: A "blanket" of natural U-238, in a so-called seed-and-blanket design ; in the first reactor about half the power came from the seed. The first Shippingport core reactor turned out to be capable of an output of 60 MWe one month after its launch. The second core was similarly designed but more powerful, having a larger seed. The highly energetic seed required more refueling cycles than the blanket in these first two cores. The third and final core used at Shippingport

186-591: A consequence of lanthanide contraction , the chemistry of hafnium and zirconium is so similar that the two cannot be separated based on differing chemical reactions. The melting and boiling points of the compounds and the solubility in solvents are the major differences in the chemistry of these twin elements. At least 40 isotopes of hafnium have been observed, ranging in mass number from 153 to 192. The five stable isotopes have mass numbers ranging from 176 to 180 inclusive. The radioactive isotopes' half-lives range from 400  ms for Hf to 7.0 × 10 years for

248-408: A direct dependency between spectral line and effective nuclear charge . This led to the nuclear charge, or atomic number of an element, being used to ascertain its place within the periodic table. With this method, Moseley determined the number of lanthanides and showed the gaps in the atomic number sequence at numbers 43, 61, 72, and 75. The discovery of the gaps led to an extensive search for

310-515: A free element on Earth, but is found combined in solid solution with zirconium in natural zirconium compounds such as zircon , ZrSiO 4 , which usually has about 1–4% of the Zr replaced by Hf. Rarely, the Hf/Zr ratio increases during crystallization to give the isostructural mineral hafnon (Hf,Zr)SiO 4 , with atomic Hf > Zr. An obsolete name for a variety of zircon containing unusually high Hf content

372-426: A geochronometer. The high and variable Lu/Hf ratios found in garnet make it useful for dating metamorphic events. Due to its heat resistance and its affinity to oxygen and nitrogen, hafnium is a good scavenger for oxygen and nitrogen in gas-filled and incandescent lamps . Hafnium is also used as the electrode in plasma cutting because of its ability to shed electrons into the air. The high energy content of Hf

434-471: A good material for nuclear reactors' control rods. Its neutron capture cross section (Capture Resonance Integral I o ≈ 2000 barns) is about 600 times that of zirconium (other elements that are good neutron-absorbers for control rods are cadmium and boron ). Excellent mechanical properties and exceptional corrosion-resistance properties allow its use in the harsh environment of pressurized water reactors . The German research reactor FRM II uses hafnium as

496-475: A heavier analog of titanium and zirconium. At the time of his formulation in 1871, Mendeleev believed that the elements were ordered by their atomic masses and placed lanthanum (element 57) in the spot below zirconium. The exact placement of the elements and the location of missing elements was done by determining the specific weight of the elements and comparing the chemical and physical properties. The X-ray spectroscopy done by Henry Moseley in 1914 showed

558-592: A light water breeder, which began operating in August 1977 and after testing was brought to full power by the end of that year. It used pellets made of thorium dioxide and uranium-233 oxide; initially the U233 content of the pellets was 5-6% in the seed region, 1.5-3% in the blanket region and none in the reflector region. It operated at 236 MWt, generating 60 MWe and ultimately produced over 2.1 billion kilowatt-hours of electricity. After five years (29,000 effective full power hours)

620-582: A melting point of 2,812 °C and a boiling point of roughly 5,100 °C, is very similar to zirconia , but slightly more basic. Hafnium carbide is the most refractory binary compound known, with a melting point over 3,890 °C, and hafnium nitride is the most refractory of all known metal nitrides, with a melting point of 3,310 °C. This has led to proposals that hafnium or its carbides might be useful as construction materials that are subjected to very high temperatures. The mixed carbide tantalum hafnium carbide ( Ta 4 HfC 5 ) possesses

682-468: A much tougher recycled plastic. Hafnium diselenide is studied in spintronics thanks to its charge density wave and superconductivity . Care needs to be taken when machining hafnium because it is pyrophoric —fine particles can spontaneously combust when exposed to air. Compounds that contain this metal are rarely encountered by most people. The pure metal is not considered toxic, but hafnium compounds should be handled as if they were toxic because

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744-402: A nearly complete separation of zirconium and hafnium is necessary for their use in nuclear power. The production of hafnium-free zirconium is the main source of hafnium. The chemical properties of hafnium and zirconium are nearly identical, which makes the two difficult to separate. The methods first used— fractional crystallization of ammonium fluoride salts or the fractional distillation of

806-589: A neutron absorber. It is also common in military reactors, particularly in US naval submarine reactors, to slow reactor rates that are too high. It is seldom found in civilian reactors, the first core of the Shippingport Atomic Power Station (a conversion of a naval reactor) being a notable exception. Hafnium is used in alloys with iron , titanium , niobium , tantalum , and other metals. An alloy used for liquid-rocket thruster nozzles, for example

868-480: A substantial role within the United States Atomic Energy Commission (AEC). The Shippingport reactor was designed to accommodate different cores during its lifetime; three were used. The first, installed in 1957, held 14.2 tons of natural uranium (the "blanket") and 165 pounds (75 kg) of high-enriched (93% U-235) uranium (the "seed"); despite this disparity in mass, about half the power

930-457: A sufficient number of neutrons to sustain an ongoing series of nuclear reactions. The International Atomic Energy Agency defines the first criticality date as the date when the reactor is made critical for the first time. This is an important milestone in the construction and commissioning of a nuclear power plant . This radioactivity –related article is a stub . You can help Misplaced Pages by expanding it . Hafnium Hafnium

992-417: A tungsten filament of 1,700 °C (3,100 °F) the reverse reaction happens preferentially, and the chemically bound iodine and hafnium dissociate into the native elements. The hafnium forms a solid coating at the tungsten filament, and the iodine can react with additional hafnium, resulting in a steady iodine turnover and ensuring the chemical equilibrium remains in favor of hafnium production. Due to

1054-652: Is alvite . A major source of zircon (and hence hafnium) ores is heavy mineral sands ore deposits , pegmatites , particularly in Brazil and Malawi , and carbonatite intrusions, particularly the Crown Polymetallic Deposit at Mount Weld , Western Australia . A potential source of hafnium is trachyte tuffs containing rare zircon-hafnium silicates eudialyte or armstrongite , at Dubbo in New South Wales , Australia. The heavy mineral sands ore deposits of

1116-483: Is a chemical element ; it has symbol Hf and atomic number 72. A lustrous , silvery gray, tetravalent transition metal , hafnium chemically resembles zirconium and is found in many zirconium minerals . Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1922, by Dirk Coster and George de Hevesy . Hafnium is named after Hafnia , the Latin name for Copenhagen , where it

1178-487: Is almost exactly canceled out by the lanthanide contraction . Hafnium changes from its alpha form, a hexagonal close-packed lattice, to its beta form, a body-centered cubic lattice, at 2388 K. The physical properties of hafnium metal samples are markedly affected by zirconium impurities, especially the nuclear properties, as these two elements are among the most difficult to separate because of their chemical similarity. A notable physical difference between these metals

1240-562: Is often used as a tracer of isotopic evolution of Earth's mantle through time. This is because Lu decays to Hf with a half-life of approximately 37 billion years. In most geologic materials, zircon is the dominant host of hafnium (>10,000 ppm) and is often the focus of hafnium studies in geology . Hafnium is readily substituted into the zircon crystal lattice , and is therefore very resistant to hafnium mobility and contamination. Zircon also has an extremely low Lu/Hf ratio, making any correction for initial lutetium minimal. Although

1302-450: Is their density , with zirconium having about one-half the density of hafnium. The most notable nuclear properties of hafnium are its high thermal neutron capture cross section and that the nuclei of several different hafnium isotopes readily absorb two or more neutrons apiece. In contrast with this, zirconium is practically transparent to thermal neutrons, and it is commonly used for the metal components of nuclear reactors—especially

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1364-460: The lanthanide contraction , the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium (IV) (0.79  angstroms ). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in

1426-467: The titanium ores ilmenite and rutile yield most of the mined zirconium, and therefore also most of the hafnium. Zirconium is a good nuclear fuel-rod cladding metal, with the desirable properties of a very low neutron capture cross section and good chemical stability at high temperatures. However, because of hafnium's neutron-absorbing properties, hafnium impurities in zirconium would cause it to be far less useful for nuclear reactor applications. Thus,

1488-509: The Lu/Hf system can be used to calculate a " model age ", i.e. the time at which it was derived from a given isotopic reservoir such as the depleted mantle , these "ages" do not carry the same geologic significance as do other geochronological techniques as the results often yield isotopic mixtures and thus provide an average age of the material from which it was derived. Garnet is another mineral that contains appreciable amounts of hafnium to act as

1550-557: The Navy, but which Eisenhower had just vetoed. Kenneth Nichols of the AEC said it "became obvious" that the Rickover-Westinghouse pressurised-water reactor intended for an aircraft carrier was "the best choice for a reactor to demonstrate the production of electricity" with Rickover "having a going organization and a reactor project under way that now had no specific use to justify it". This

1612-491: The Shippingport power plant operated for about 80,324 hours, producing about 7.4 billion kilowatt-hours of electricity. Owing to these peculiarities, some non-governmental sources label Shippingport a "demonstration PWR reactor" and consider that the "first fully commercial PWR" in the US was Yankee Rowe . Criticism centers on the fact that the Shippingport plant had not been built to commercial specifications. Consequently,

1674-452: The U.S. Nuclear Regulatory Commission (NRC) notifying Yankee in August that the former plant site had been fully decommissioned in accordance with NRC procedures and regulations; Maine Yankee Nuclear Power Plant completely decommissioned in 2005; and Connecticut Yankee Nuclear Power Plant . All three prior commercial reactor sites have been returned to greenfield conditions and are open to visitors. Criticality (status) In

1736-443: The chloride —have not proven suitable for an industrial-scale production. After zirconium was chosen as a material for nuclear reactor programs in the 1940s, a separation method had to be developed. Liquid–liquid extraction processes with a wide variety of solvents were developed and are still used for producing hafnium. About half of all hafnium metal manufactured is produced as a by-product of zirconium refinement. The end product of

1798-417: The cladding of their nuclear fuel rods . Hafnium reacts in air to form a protective film that inhibits further corrosion . Despite this, the metal is attacked by hydrofluoric acid and concentrated sulfuric acid, and can be oxidized with halogens or burnt in air. Like its sister metal zirconium, finely divided hafnium can ignite spontaneously in air. The metal is resistant to concentrated alkalis . As

1860-559: The construction cost per kilowatt at Shippingport was about ten times those for a conventional power plant. In 1953, US President Dwight D. Eisenhower gave his Atoms for Peace speech to the United Nations . Commercial nuclear power generation was cornerstone of his plan. A proposal by Duquesne Light Company was accepted by Admiral Rickover and the plans for the Shippingport Atomic Power Station started. Ground

1922-534: The core was removed and found to contain nearly 1.4% more fissile material than when it was installed, demonstrating that breeding had occurred. On October 1, 1982, the reactor ceased operations after 25 years. Dismantlement of the facility began in September 1985. In December 1988, the 956-ton (870-T) reactor pressure vessel/neutron shield tank assembly was lifted out of the containment building and loaded onto land transportation equipment in preparation for removal from

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1984-602: The element being named for the Latin name for "Copenhagen", Hafnia , the home town of Niels Bohr . Today, the Faculty of Science of the University of Copenhagen uses in its seal a stylized image of the hafnium atom. Hafnium was separated from zirconium through repeated recrystallization of the double ammonium or potassium fluorides by Valdemar Thal Jantzen and von Hevesey. Anton Eduard van Arkel and Jan Hendrik de Boer were

2046-431: The environment, thus making elements 75 ( rhenium ) and 72 (hafnium) the last two unknown non-radioactive elements. Most of the hafnium produced is used in the manufacture of control rods for nuclear reactors . Hafnium has limited technical applications due to a few factors. First, it's very similar to zirconium, a more abundant element that can be used in most cases. Second, pure hafnium wasn't widely available until

2108-405: The first to prepare metallic hafnium by passing hafnium tetraiodide vapor over a heated tungsten filament in 1924. This process for differential purification of zirconium and hafnium is still in use today. Hafnium was one of the last two stable elements to be discovered. The element rhenium was found in 1908 by Masataka Ogawa , though its atomic number was misidentified at the time, and it

2170-461: The highest melting point of any currently known compound, 4,263 K (3,990 °C; 7,214 °F). Recent supercomputer simulations suggest a hafnium alloy with a melting point of 4,400 K. Hafnium's existence was predicted by Dmitri Mendeleev in 1869. In his report on The Periodic Law of the Chemical Elements , in 1869, Dmitri Mendeleev had implicitly predicted the existence of

2232-534: The ionic forms of metals are normally at greatest risk for toxicity, and limited animal testing has been done for hafnium compounds. People can be exposed to hafnium in the workplace by breathing, swallowing, skin, and eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit ( permissible exposure limit ) for exposure to hafnium and hafnium compounds in the workplace as TWA 0.5 mg/m over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set

2294-531: The late 1950s, when it became a byproduct of the nuclear industry's need for hafnium-free zirconium. Additionally, hafnium is rare and difficult to separate from other elements, making it expensive. After the Fukushima disaster reduced the demand for hafnium-free zirconium, the price of hafnium increased significantly from around $ 500–600/kg in 2014 to around $ 1000/kg in 2015. The nuclei of several hafnium isotopes can each absorb multiple neutrons. This makes hafnium

2356-467: The main engine of the Apollo Lunar Modules , is C103 which consists of 89% niobium, 10% hafnium and 1% titanium. Small additions of hafnium increase the adherence of protective oxide scales on nickel-based alloys. It thereby improves the corrosion resistance, especially under cyclic temperature conditions that tend to break oxide scales, by inducing thermal stresses between the bulk material and

2418-422: The missing elements. In 1914, several people claimed the discovery after Henry Moseley predicted the gap in the periodic table for the then-undiscovered element 72. Georges Urbain asserted that he found element 72 in the rare earth elements in 1907 and published his results on celtium in 1911. Neither the spectra nor the chemical behavior he claimed matched with the element found later, and therefore his claim

2480-506: The most stable one, the primordial Hf. The extinct radionuclide Hf has a half-life of 8.9 ± 0.1 million years , and is an important tracker isotope for the formation of planetary cores . The nuclear isomer Hf was at the center of a controversy for several years regarding its potential use as a weapon. Hafnium is estimated to make up about between 3.0 and 4.8 ppm of the Earth 's upper crust by mass. It does not exist as

2542-430: The operation of a nuclear reactor , criticality is the state in which a nuclear chain reaction is self-sustaining—that is, when reactivity is zero. In supercritical states, reactivity is greater than zero. Criticality is the normal operating condition of a nuclear reactor, in which nuclear fuel sustains a fission chain reaction . A reactor achieves criticality (and is said to be critical) when each fission releases

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2604-603: The oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen , nitrogen , carbon , boron , sulfur , and silicon . Some hafnium compounds in lower oxidation states are known. Hafnium(IV) chloride and hafnium(IV) iodide have some applications in the production and purification of hafnium metal. They are volatile solids with polymeric structures. These tetrachlorides are precursors to various organohafnium compounds such as hafnocene dichloride and tetrabenzylhafnium. The white hafnium oxide (HfO 2 ), with

2666-529: The oxide layer. Hafnium-based compounds are employed in gates of transistors as insulators in the 45 nm (and below) generation of integrated circuits from Intel , IBM and others. Hafnium oxide-based compounds are practical high-k dielectrics , allowing reduction of the gate leakage current which improves performance at such scales. Isotopes of hafnium and lutetium (along with ytterbium ) are also used in isotope geochemistry and geochronological applications, in lutetium-hafnium dating . It

2728-440: The project explains why the Shippingport reactor used 93%-enriched uranium, unlike later commercial power reactors that do not exceed 5% enrichment. Other significant differences from commercial reactors include the use of hafnium for its control rods , although these were necessary and used only in the reactor's seed. Shippingport was created and operated under the auspices of Admiral Hyman G. Rickover , whose authority included

2790-400: The same seed-and-blanket design. For the second core, the seed volume was 21% of the total core volume. The second core thus required only one seed refueling. It began operating in 1965 and over the next nine years generated almost 3.5 billion kilowatt-hours of electricity. In 1974 the turbine-generator suffered mechanical failure, causing the plant to be shut down. The third and final core was

2852-443: The same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors . Hafnium is a shiny, silvery, ductile metal that is corrosion -resistant and chemically similar to zirconium in that they have the same number of valence electrons and are in the same group. Also, their relativistic effects are similar: The expected expansion of atomic radii from period 5 to 6

2914-453: The separation is hafnium(IV) chloride . The purified hafnium(IV) chloride is converted to the metal by reduction with magnesium or sodium , as in the Kroll process . Further purification is effected by a chemical transport reaction developed by Arkel and de Boer : In a closed vessel, hafnium reacts with iodine at temperatures of 500 °C (900 °F), forming hafnium(IV) iodide ; at

2976-429: The simplest hafnium metallocene is hafnocene dichloride. Hafnium metallocenes are part of a large collection of Group 4 transition metal metallocene catalysts that are used worldwide in the production of polyolefin resins like polyethylene and polypropylene . A pyridyl-amidohafnium catalyst can be used for the controlled iso-selective polymerization of propylene which can then be combined with polyethylene to make

3038-614: The site and shipment to a burial facility in Washington State. The site has been cleaned up and released for unrestricted use. While the Shippingport Reactor has been decommissioned, Beaver Valley Nuclear Generating Station Units 1 and 2 are still licensed and in operation at the site. The $ 98 million (1985 estimate) cleanup of Shippingport has been used as an example of a successful reactor decommissioning by proponents of nuclear power; however, critics point out that Shippingport

3100-694: The vessel plus the weight of a structural steel shipping skid) and was successfully shipped by waterway for burial at the Hanford Reservation . The reactor vessel from Trojan Nuclear Power Plant (located in Oregon), was also successfully shipped by waterway to the Hanford site; a much shorter trip than the Shippingport reactor. Subsequent to Shippingport's decommissioning , three other large commercial reactors have been entirely leveled: Yankee Rowe Nuclear Power Station having been entirely decommissioned in 2007 with

3162-503: Was a rare earth element discovered in 1911, Dirk Coster and Georg von Hevesy were motivated to search for the new element in zirconium ores. Hafnium was discovered by the two in 1923 in Copenhagen, Denmark, validating the original 1869 prediction of Mendeleev. It was ultimately found in zircon in Norway through X-ray spectroscopy analysis. The place where the discovery took place led to

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3224-571: Was accepted by Lewis Strauss and the Commission in January 1954. The acceptance of Duquesne Light as the utility partner was announced on 11 March. The ground-breaking ceremony was initiated by Eisenhower from Denver where he was giving a talk on atomic energy on Labor Day; Rickover ensured that the unmanned bulldozer pushing dirt did not dig in and stall by having the dozer blade riding along two railroad rails buried under six inches of dirt. The origin of

3286-408: Was an experimental, light water moderated, thermal breeder reactor . It kept the same seed-and-blanket design, but the seed was now uranium-233 and the blanket was made of thorium . Being a breeder reactor, it had the ability to transmute relatively inexpensive thorium to uranium-233 as part of its fuel cycle. The breeding ratio attained by Shippingport's third core was 1.01. Over its 25-year life,

3348-453: Was broken on Labor Day, September 6, 1954. President Eisenhower remotely initiated the first scoop of dirt at the ceremony. The reactor achieved first criticality at 4:30 AM on December 2, 1957. Sixteen days later, on December 18, the first electrical power was generated and full power was achieved on December 23, 1957, although the station remained in test mode. Eisenhower opened the Shippingport Atomic Power Station on May 26, 1958. The plant

3410-403: Was built in 32 months at a cost of $ 72.5 million (equivalent to $ 786,504,739 in 2023). The type of reactor used at Shippingport was a matter of expediency. The Atomic Energy Commission urged the construction of a reactor integrated into the utility grid. The only suitable reactor available at the time was the one that was intended for the nuclear-powered aircraft carrier desired by

3472-469: Was discovered. Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nanometers and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium , titanium , or tungsten . Hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants , but at

3534-431: Was generated in the seed. The seed was depleted quicker than the blanket, and it was replenished three times during the lifetime of the first core. Seven years later (when running on its fourth seed) the first core was retired, after having produced 1.8 billion kilowatt-hours of electricity. The second core had increased generating capacity (more than five times) and instrumentation to measure performance, but otherwise used

3596-442: Was not generally recognised by the scientific community until its rediscovery by Walter Noddack , Ida Noddack , and Otto Berg in 1925. This makes it somewhat difficult to say if hafnium or rhenium was discovered last. In 1923, six predicted elements were still missing from the periodic table: 43 ( technetium ), 61 ( promethium ), 85 ( astatine ), and 87 ( francium ) are radioactive elements and are only present in trace amounts in

3658-448: Was not part of the rare earth elements group. By early 1923, Niels Bohr and others agreed with Bury. These suggestions were based on Bohr's theories of the atom which were identical to chemist Charles Bury, the X-ray spectroscopy of Moseley, and the chemical arguments of Friedrich Paneth . Encouraged by these suggestions and by the reappearance in 1922 of Urbain's claims that element 72

3720-606: Was smaller than most commercial nuclear power plants , most reactors in the United States are about 1,000 MWe, while Shippingport was only 60 MWe. Others argue that it was an excellent test case to prove a reactor site could be safely decommissioned and a site released for unrestricted use. Shippingport, while somewhat smaller than a large commercial reactor today, was representative, with four steam generators, pressurizer and reactor. The reactor alone, when packaged for shipment, weighed in excess of 1000 tons (921 tons weight of

3782-468: Was the concern of a DARPA -funded program in the US. This program eventually concluded that using the above-mentioned Hf nuclear isomer of hafnium to construct high-yield weapons with X-ray triggering mechanisms—an application of induced gamma emission —was infeasible because of its expense. See hafnium controversy . Hafnium metallocene compounds can be prepared from hafnium tetrachloride and various cyclopentadiene -type ligand species. Perhaps

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3844-425: Was turned down after a long-standing controversy. The controversy was partly because the chemists favored the chemical techniques which led to the discovery of celtium , while the physicists relied on the use of the new X-ray spectroscopy method that proved that the substances discovered by Urbain did not contain element 72. In 1921, Charles R. Bury suggested that element 72 should resemble zirconium and therefore

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