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102-448: Initially designed for 15 MW th , the MSRE was operated at 7.4 MW th because of imprecise nuclear cross section data. It was a test reactor simulating the neutronic "kernel" of a type of inherently safer epithermal thorium breeder reactor called the liquid fluoride thorium reactor . It primarily used two fuels: first uranium-235 and later uranium-233 . The latter UF 4

204-467: A Xe nucleus has a spin of 1/2, and therefore a zero electric quadrupole moment , the Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and the hyperpolarization persists for long periods even after the engendering light and vapor have been removed. Spin polarization of Xe can persist from several seconds for xenon atoms dissolved in blood to several hours in

306-486: A gas-filled tube , xenon emits a blue or lavenderish glow when excited by electrical discharge . Xenon emits a band of emission lines that span the visual spectrum, but the most intense lines occur in the region of blue light, producing the coloration. Xenon is a trace gas in Earth's atmosphere , occurring at a volume fraction of 87 ± 1 nL/L ( parts per billion ), or approximately 1 part per 11.5 million. It

408-558: A light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360  kJ . This same amount of energy would light a 40-watt bulb for 2.5 hours, or a 50-watt bulb for 2 hours. Power stations are rated using units of power, typically megawatts or gigawatts (for example, the Three Gorges Dam in China is rated at approximately 22 gigawatts). This reflects

510-492: A constant opposing force of one newton , the rate at which work is done is one watt. 1   W = 1   J / s = 1   N ⋅ m / s = 1   k g ⋅ m 2 ⋅ s − 3 . {\displaystyle \mathrm {1~W=1~J{/}s=1~N{\cdot }m{/}s=1~kg{\cdot }m^{2}{\cdot }s^{-3}} .} In terms of electromagnetism , one watt

612-465: A density of 5.894 kg/m , about 4.5 times the density of the Earth's atmosphere at sea level, 1.217 kg/m . As a liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point. Liquid xenon has a high polarizability due to its large atomic volume, and thus is an excellent solvent. It can dissolve hydrocarbons, biological molecules, and even water. Under

714-453: A fission product generated in the fuel. This was first noted in the specimens that were removed from the core at intervals during the reactor operation. Post-operation examination of pieces of a control-rod thimble, heat-exchanger tubes and pump bowl parts revealed the ubiquity of the cracking and emphasized its importance to the MSR concept. The crack growth was rapid enough to become a problem over

816-558: A higher mass fraction in spent nuclear fuel (which is about 3% fission products) than it does in air. However, there is as of 2022 no commercial effort to extract xenon from spent fuel during nuclear reprocessing . Naturally occurring xenon is composed of seven stable isotopes : Xe, Xe, and Xe. The isotopes Xe and Xe are predicted by theory to undergo double beta decay , but this has never been observed so they are considered stable. In addition, more than 40 unstable isotopes have been studied. The longest-lived of these isotopes are

918-438: A large number of xenon compounds have been discovered and described. Almost all known xenon compounds contain the electronegative atoms fluorine or oxygen. The chemistry of xenon in each oxidation state is analogous to that of the neighboring element iodine in the immediately lower oxidation state. Three fluorides are known: XeF 2 , XeF 4 , and XeF 6 . XeF is theorized to be unstable. These are

1020-504: A pale-yellow solid. It explodes above −35.9 °C into xenon and oxygen gas, but is otherwise stable. A number of xenon oxyfluorides are known, including XeOF 2 , XeOF 4 , XeO 2 F 2 , and XeO 3 F 2 . XeOF 2 is formed by reacting OF 2 with xenon gas at low temperatures. It may also be obtained by partial hydrolysis of XeF 4 . It disproportionates at −20 °C into XeF 2 and XeO 2 F 2 . XeOF 4

1122-450: A period of one year: equivalent to approximately 114 megawatts of constant power output. The watt-second is a unit of energy, equal to the joule . One kilowatt hour is 3,600,000 watt seconds. While a watt per hour is a unit of rate of change of power with time, it is not correct to refer to a watt (or watt-hour) as a watt per hour. Xenon Xenon is a chemical element ; it has symbol Xe and atomic number 54. It

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1224-465: A potential for a nuclear criticality accident , as well as a potentially dangerous build-up of fluorine gas: the environment above the solidified salt was approximately one atmosphere of fluorine. The ensuing decontamination and decommissioning project was called "the most technically challenging" activity assigned to Bechtel Jacobs under its environmental management contract with the U.S. Department of Energy's Oak Ridge Operations organization. In 2003,

1326-493: A reactor after a scram or increasing power after it had been reduced and it was one of several contributing factors in the Chernobyl nuclear accident . Stable or extremely long lived isotopes of xenon are also produced in appreciable quantities in nuclear fission. Xenon-136 is produced when xenon-135 undergoes neutron capture before it can decay. The ratio of xenon-136 to xenon-135 (or its decay products) can give hints as to

1428-588: A real compound. Theoretical calculations indicate that the linear molecule XeCl 2 is less stable than the van der Waals complex. Xenon tetrachloride and xenon dibromide are even more unstable and they cannot be synthesized by chemical reactions. They were created by radioactive decay of ICl 4 and IBr 2 , respectively. Three oxides of xenon are known: xenon trioxide ( XeO 3 ) and xenon tetroxide ( XeO 4 ), both of which are dangerously explosive and powerful oxidizing agents, and xenon dioxide (XeO 2 ), which

1530-477: A technology capable of manipulating individual atoms . The program, called IBM in atoms , used a scanning tunneling microscope to arrange 35 individual xenon atoms on a substrate of chilled crystal of nickel to spell out the three-letter company initialism. It was the first-time atoms had been precisely positioned on a flat surface. Xenon has atomic number 54; that is, its nucleus contains 54 protons . At standard temperature and pressure , pure xenon gas has

1632-541: A turbine, which generates 648 MW e (i.e. electricity). Other SI prefixes are sometimes used, for example gigawatt electrical (GW e ). The International Bureau of Weights and Measures , which maintains the SI-standard, states that further information about a quantity should not be attached to the unit symbol but instead to the quantity symbol (e.g., P th = 270 W rather than P = 270 W th ) and so these unit symbols are non-SI. In compliance with SI,

1734-495: A unit of time, namely 1 J/s. In this new definition, 1 absolute watt = 1.00019 international watts. Texts written before 1948 are likely to be using the international watt, which implies caution when comparing numerical values from this period with the post-1948 watt. In 1960, the 11th General Conference on Weights and Measures adopted the absolute watt into the International System of Units (SI) as

1836-412: A variety of shapes of material for the MSRE were produced commercially. Requests for bids on component fabrication went to several companies in the nuclear fabrication industry, but all declined to submit lump-sum bids because of lack of experience with the new alloy. Consequently, all major components were fabricated in U.S. Atomic Energy Commission -owned shops at Oak Ridge and Paducah, Kentucky . At

1938-557: Is 1.56 × 10 , for an abundance of approximately one part in 630 thousand of the total mass. Xenon is relatively rare in the Sun 's atmosphere, on Earth , and in asteroids and comets . The abundance of xenon in the atmosphere of planet Jupiter is unusually high, about 2.6 times that of the Sun. This abundance remains unexplained, but may have been caused by an early and rapid buildup of planetesimals —small, sub-planetary bodies—before

2040-432: Is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate , the first noble gas compound to be synthesized. Xenon is used in flash lamps and arc lamps , and as a general anesthetic . The first excimer laser design used a xenon dimer molecule (Xe 2 ) as

2142-421: Is a notable neutron poison with a high fission product yield . As it is relatively short lived, it decays at the same rate it is produced during steady operation of a nuclear reactor. However, if power is reduced or the reactor is scrammed , less xenon is destroyed than is produced from the beta decay of its parent nuclides . This phenomenon called xenon poisoning can cause significant problems in restarting

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2244-401: Is also found as a component of gases emitted from some mineral springs . Given a total mass of the atmosphere of 5.15 × 10 kilograms (1.135 × 10  lb), the atmosphere contains on the order of 2.03 gigatonnes (2.00 × 10 long tons; 2.24 × 10 short tons) of xenon in total when taking the average molar mass of the atmosphere as 28.96 g/mol which is equivalent to some 394-mass ppb. Xenon

2346-482: Is extracted either by adsorption onto silica gel or by distillation. Finally, the krypton/xenon mixture may be separated into krypton and xenon by further distillation. Worldwide production of xenon in 1998 was estimated at 5,000–7,000 cubic metres (180,000–250,000 cu ft). At a density of 5.894 grams per litre (0.0002129 lb/cu in) this is equivalent to roughly 30 to 40 tonnes (30 to 39 long tons; 33 to 44 short tons). Because of its scarcity, xenon

2448-459: Is formed by the partial hydrolysis of XeF 6 ... ...or the reaction of XeF 6 with sodium perxenate, Na 4 XeO 6 . The latter reaction also produces a small amount of XeO 3 F 2 . XeO 2 F 2 is also formed by partial hydrolysis of XeF 6 . XeOF 4 reacts with CsF to form the XeOF 5 anion, while XeOF 3 reacts with

2550-543: Is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10  € /L (=~€1.7/g) for xenon, 1 €/L (=~€0.27/g) for krypton, and 0.20 €/L (=~€0.22/g) for neon, while the much more plentiful argon, which makes up over 1% by volume of earth's atmosphere, costs less than a cent per liter. Within the Solar System, the nucleon fraction of xenon

2652-733: Is named after the Scottish inventor James Watt . The unit name was proposed by C. William Siemens in August 1882 in his President's Address to the Fifty-Second Congress of the British Association for the Advancement of Science . Noting that units in the practical system of units were named after leading physicists, Siemens proposed that watt might be an appropriate name for a unit of power. Siemens defined

2754-406: Is obtained commercially as a by-product of the separation of air into oxygen and nitrogen . After this separation, generally performed by fractional distillation in a double-column plant, the liquid oxygen produced will contain small quantities of krypton and xenon. By additional fractional distillation, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which

2856-523: Is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit). 1   W = 1   V ⋅ A . {\displaystyle \mathrm {1~W=1~V{\cdot }A} .} Two additional unit conversions for watt can be found using

2958-451: Is to be removed from the fuel as the hexafluoride by adding excess fluorine, and plutonium as the plutonium dioxide by adding sodium carbonate . 35°55′18″N 84°18′24″W  /  35.92178°N 84.30672°W  / 35.92178; -84.30672 MWth The watt (symbol: W ) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m ⋅s . It

3060-530: Is used to quantify the rate of energy transfer . The watt is named in honor of James Watt (1736–1819), an 18th-century Scottish inventor , mechanical engineer , and chemist who improved the Newcomen engine with his own steam engine in 1776. Watt's invention was fundamental for the Industrial Revolution . When an object's velocity is held constant at one meter per second against

3162-513: Is weakly acidic, dissolving in alkali to form unstable xenate salts containing the HXeO 4 anion. These unstable salts easily disproportionate into xenon gas and perxenate salts, containing the XeO 6 anion. Barium perxenate, when treated with concentrated sulfuric acid , yields gaseous xenon tetroxide: To prevent decomposition, the xenon tetroxide thus formed is quickly cooled into

Molten-Salt Reactor Experiment - Misplaced Pages Continue

3264-432: The gas phase and several days in deeply frozen solid xenon. In contrast, Xe has a nuclear spin value of 3 ⁄ 2 and a nonzero quadrupole moment , and has t 1 relaxation times in the millisecond and second ranges. Some radioactive isotopes of xenon (for example, Xe and Xe) are produced by neutron irradiation of fissionable material within nuclear reactors . Xe is of considerable significance in

3366-409: The lasing medium , and the earliest laser designs used xenon flash lamps as pumps . Xenon is also used to search for hypothetical weakly interacting massive particles and as a propellant for ion thrusters in spacecraft. Naturally occurring xenon consists of seven stable isotopes and two long-lived radioactive isotopes. More than 40 unstable xenon isotopes undergo radioactive decay , and

3468-404: The moderator . Before the MSRE development began, tests had shown that salt would not permeate graphite in which the pores were on the order of a micrometer. However, graphite with the desired pore structure was available only in small, experimentally prepared pieces, and when a manufacturer set out to produce a new grade (CGB) to meet the MSRE requirements, difficulties were encountered. The fuel

3570-429: The primordial Xe, which undergoes double electron capture with a half-life of 1.8 × 10  yr , and Xe, which undergoes double beta decay with a half-life of 2.11 × 10 yr . Xe is produced by beta decay of I , which has a half-life of 16 million years. Xe, Xe, Xe, and Xe are some of the fission products of U and Pu , and are used to detect and monitor nuclear explosions. Nuclei of two of

3672-441: The 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography . This led him to the invention of the xenon flash lamp in which light is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method. In 1939, American physician Albert R. Behnke Jr. began exploring

3774-465: The MSRE agreed with conventional design calculations and did not change over the life of the reactor. Limiting oxygen in the salt proved effective, and the tendency of fission products to be dispersed from contaminated equipment during maintenance was low. Operation of the MSRE provided insights into the problem of tritium in a molten-salt reactor. It was observed that about 6–10% of the calculated 54 Ci/day (2.0  TBq ) production diffused out of

3876-612: The MSRE cleanup project was estimated at $ 130 million, with decommissioning expected to be completed in 2009. Removal of uranium from the salt was completed in March 2008, however still leaving the salt with the fission products in the tanks. Much of the high cost was caused by the unpleasant surprise of fluorine and uranium hexafluoride evolution from cold fuel salt in storage that ORNL did not defuel and store correctly, but this has now been taken into consideration in MSR design. A potential decommissioning process has been described; uranium

3978-406: The MSRE experience was that a molten salt fueled reactor concept was viable. It ran for considerable periods of time, yielding valuable information, and maintenance was accomplished safely and without excessive delay. The MSRE confirmed expectations and predictions. For example, it was demonstrated that: the fuel salt was immune to radiation damage, the graphite was not attacked by the fuel salt, and

4080-401: The MSRE was on the basis of the promising results of tests at aircraft nuclear propulsion conditions and the availability of much of the required metallurgical data. Development for the MSRE generated the further data required for ASME code approval. It also included preparation of standards for Hastelloy-N procurement and for component fabrication. Almost 200,000 lb (90,000 kg) in

4182-470: The above equation and Ohm's law . 1   W = 1   V 2 / Ω = 1   A 2 ⋅ Ω , {\displaystyle \mathrm {1~W=1~V^{2}/\Omega =1~A^{2}{\cdot }\Omega } ,} where ohm ( Ω {\displaystyle \Omega } ) is the SI derived unit of electrical resistance . The watt

Molten-Salt Reactor Experiment - Misplaced Pages Continue

4284-420: The alkali metal fluorides KF , RbF and CsF to form the XeOF 4 anion. Xenon can be directly bonded to a less electronegative element than fluorine or oxygen, particularly carbon . Electron-withdrawing groups, such as groups with fluorine substitution, are necessary to stabilize these compounds. Numerous such compounds have been characterized, including: Other compounds containing xenon bonded to

4386-421: The causes of "drunkenness" in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, and discovered that this caused the divers to perceive a change in depth. From his results, he deduced that xenon gas could serve as an anesthetic . Although Russian toxicologist Nikolay V. Lazarev apparently studied xenon anesthesia in 1941, the first published report confirming xenon anesthesia

4488-529: The circulating loop. The circulating gas and the power fluctuations that accompanied it were eliminated by operating the fuel pump at slightly lower speed. Operation at high power for several months permitted accurate measurement of the capture -to- fission ratio, for U in this reactor, completing the objectives of the U operation. In the concluding months of operation, xenon stripping, deposition of fission products, and tritium behavior were investigated. The feasibility of using plutonium in molten-salt reactors

4590-468: The core. Most of the MSRE effort from 1960 through 1964 was devoted to design, development, and construction of the MSRE. Production and further testing of graphite and Hastelloy-N, both in-pile and out, were major development activities. Others included work on reactor chemistry , development of fabrication techniques for Hastelloy-N, development of reactor components, and remote-maintenance planning and preparations. The MSRE operated for 5 years. The salt

4692-541: The corrosion of Hastelloy-N was negligible. Noble gases were stripped from the fuel salt by a spray system, reducing the Xe poisoning by a factor of about 6. The bulk of the fission product elements remained stable in the salt. Additions of uranium and plutonium to the salt during operation were quick and uneventful, and recovery of uranium by fluorination was efficient. The neutronics, including critical loading, reactivity coefficients, dynamics, and long-term reactivity changes, agreed with prior calculations. In other areas,

4794-682: The design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel ). Xe reactor poisoning was a major factor in the Chernobyl disaster . A shutdown or decrease of power of a reactor can result in buildup of Xe, with reactor operation going into a condition known as the iodine pit . Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may emanate from cracked fuel rods , or fissioning of uranium in cooling water . Isotope ratios of xenon produced in natural nuclear fission reactors at Oklo in Gabon reveal

4896-464: The elements krypton and neon . They found xenon in the residue left over from evaporating components of liquid air . Ramsay suggested the name xenon for this gas from the Greek word ξένον xénon , neuter singular form of ξένος xénos , meaning 'foreign(er)', 'strange(r)', or 'guest'. In 1902, Ramsay estimated the proportion of xenon in the Earth's atmosphere to be one part in 20 million. During

4998-515: The energy company Ørsted A/S uses the unit megawatt for produced electrical power and the equivalent unit megajoule per second for delivered heating power in a combined heat and power station such as Avedøre Power Station . When describing alternating current (AC) electricity, another distinction is made between the watt and the volt-ampere . While these units are equivalent for simple resistive circuits , they differ when loads exhibit electrical reactance . Radio stations usually report

5100-400: The fluid salt would permit on-site chemical separation of the fuel and wastes. The fuel system was located in sealed cells, laid out for maintenance with long-handled tools through openings in the top shielding. A tank of LiF-BeF 2 salt was used to flush the fuel circulating system before and after maintenance. In a cell adjacent to the reactor was a simple facility for bubbling gas through

5202-419: The form of an overabundance of xenon-129. He inferred that this was a decay product of radioactive iodine-129 . This isotope is produced slowly by cosmic ray spallation and nuclear fission , but is produced in quantity only in supernova explosions. Because the half-life of I is comparatively short on a cosmological time scale (16 million years), this demonstrated that only a short time had passed between

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5304-432: The fuel or flush salt: H 2 - hydrogen fluoride mixture, in roughly 10:1 ratio, to remove oxide, fluorine to remove uranium as uranium hexafluoride . The secondary coolant was LiF-BeF 2 (66–34 mole %). The bowl of the fuel pump was the surge space for the circulating loop, and here about 50 US gallons per minute (190 L/min) of fuel was sprayed into the gas space to allow xenon and krypton to escape from

5406-505: The fuel sampler-enricher. Centrifugal pumps were developed similar to those used successfully in the aircraft reactor program, but with provisions for remote maintenance, and including a spray system for xenon removal. Remote maintenance considerations pervaded the MSRE design, and developments included devices for remotely cutting and brazing together 1 + 1 ⁄ 2 inches (38 mm) pipe, removable heater-insulation units, and equipment for removing specimens of metal and graphite from

5508-404: The fuel system into the containment cell atmosphere and another 6–10% reached the air through the heat removal system. The fact that these fractions were not higher, indicated that something partially negated the transfer of tritium through hot metals. One unexpected finding was inter-granular cracking in all metal surfaces exposed to the fuel salt. The cause of the embrittlement was tellurium ,

5610-411: The gas platinum hexafluoride (PtF 6 ) was a powerful oxidizing agent that could oxidize oxygen gas (O 2 ) to form dioxygenyl hexafluoroplatinate ( O 2 [PtF 6 ] ). Since O 2 (1165 kJ/mol) and xenon (1170 kJ/mol) have almost the same first ionization potential , Bartlett realized that platinum hexafluoride might also be able to oxidize xenon. On March 23, 1962, he mixed

5712-499: The hcp phase. It is completely metallic at 155 GPa. When metallized, xenon appears sky blue because it absorbs red light and transmits other visible frequencies. Such behavior is unusual for a metal and is explained by the relatively small width of the electron bands in that state. Liquid or solid xenon nanoparticles can be formed at room temperature by implanting Xe ions into a solid matrix. Many solids have lattice constants smaller than solid Xe. This results in compression of

5814-488: The heating of the presolar disk ; otherwise, xenon would not have been trapped in the planetesimal ices. The problem of the low terrestrial xenon may be explained by covalent bonding of xenon to oxygen within quartz , reducing the outgassing of xenon into the atmosphere. Unlike the lower-mass noble gases, the normal stellar nucleosynthesis process inside a star does not form xenon. Nucleosynthesis consumes energy to produce nuclides more massive than iron-56 , and thus

5916-433: The implanted Xe to pressures that may be sufficient for its liquefaction or solidification. Xenon is a member of the zero- valence elements that are called noble or inert gases . It is inert to most common chemical reactions (such as combustion, for example) because the outer valence shell contains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound. In

6018-573: The isotope ratios of xenon are an important tool for studying the early history of the Solar System . Radioactive xenon-135 is produced by beta decay from iodine-135 (a product of nuclear fission ), and is the most significant (and unwanted) neutron absorber in nuclear reactors . Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers on July 12, 1898, shortly after their discovery of

6120-460: The maximum power output it can achieve at any point in time. A power station's annual energy output, however, would be recorded using units of energy (not power), typically gigawatt hours. Major energy production or consumption is often expressed as terawatt hours for a given period; often a calendar year or financial year. One terawatt hour of energy is equal to a sustained power delivery of one terawatt for one hour, or approximately 114 megawatts for

6222-460: The mid-1980s, there was concern that radioactivity was migrating through the system, reported by an ORNL employee who was among 125 people working above the reactor, which had not been decontaminated or decommissioned. Department of Energy Oak Ridge Operations Manager Joe Ben LaGrone ordered evacuation of 125 employees, based on findings reported to him inspector William Dan DeFord, P.E. Sampling in 1994 revealed concentrations of uranium that created

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6324-492: The operation of nuclear fission reactors . Xe has a huge cross section for thermal neutrons , 2.6×10   barns , and operates as a neutron absorber or " poison " that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production. However, the designers had made provisions in

6426-478: The operation resulted in improved data or reduced uncertainties. The U capture-to- fission ratio in a typical MSR neutron spectrum is an example of basic data that was improved. The effect of fissioning on the redox potential of the fuel salt was resolved. The deposition of some elements (" noble metals ") was expected, but the MSRE provided quantitative data on relative deposition on graphite, metal, and liquid-gas interfaces. Heat transfer coefficients measured in

6528-452: The original objectives of the MSRE had been accomplished, and nuclear operation with U was concluded. By this time, ample U had become available, so the MSRE program was extended to include substitution of U for the uranium in the fuel salt, and operation to observe the new nuclear characteristics. Using the on-site processing equipment the flush salt and fuel salt were fluorinated to recover the uranium in them as UF 6 . UF 4 -LiF eutectic

6630-479: The planned 30-year life of a follow-on thorium breeder reactor. This cracking could in short-term be reduced by adding small amounts of niobium to the Hastelloy-N. However, further studies were needed to assess the effects of longer exposure times and some interaction parameters for the used mixtures. The operation experience gained with the MSRE showed that the following areas require further investigation for

6732-469: The power history of a given reactor and the absence of xenon-136 is a "fingerprint" for nuclear explosions, as xenon-135 is not produced directly but as a product of successive beta decays and thus it cannot absorb any neutrons in a nuclear explosion which occurs in fractions of a second. The stable isotope xenon-132 has a fission product yield of over 4% in the thermal neutron fission of U which means that stable or nearly stable xenon isotopes have

6834-488: The power of their transmitters in units of watts, referring to the effective radiated power . This refers to the power that a half-wave dipole antenna would need to radiate to match the intensity of the transmitter's main lobe . The terms power and energy are closely related but distinct physical quantities. Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time . For example, when

6936-553: The presence of NaF yields high-purity XeF 4 . The xenon fluorides behave as both fluoride acceptors and fluoride donors, forming salts that contain such cations as XeF and Xe 2 F 3 , and anions such as XeF 5 , XeF 7 , and XeF 8 . The green, paramagnetic Xe 2 is formed by the reduction of XeF 2 by xenon gas. XeF 2 also forms coordination complexes with transition metal ions. More than 30 such complexes have been synthesized and characterized. Whereas

7038-439: The pump bowl was a port through which salt samples could be taken or capsules of concentrated fuel-enriching salt (UF 4 -LiF or PuF 3 ) could be introduced. At the time, the high temperatures were seen almost as a disadvantage because they hampered use of conventional steam turbines . Now, such temperatures are seen as an opportunity to use high-efficiency closed-cycle gas turbines . After two months of high-power operation,

7140-507: The reactor properties during chain reaction that took place about 2 billion years ago. Because xenon is a tracer for two parent isotopes, xenon isotope ratios in meteorites are a powerful tool for studying the formation of the Solar System . The iodine–xenon method of dating gives the time elapsed between nucleosynthesis and the condensation of a solid object from the solar nebula . In 1960, physicist John H. Reynolds discovered that certain meteorites contained an isotopic anomaly in

7242-451: The reactor was down for 3 months because of the failure of one of the main cooling blowers. The reactor experienced stable neutronic operation . If temperatures increased or bubbles formed, the volume of the fluid fuel salts would increase and some fluid fuel salts would be forced out of the core, thereby reducing the reactivity . The MSRE development program did not include reactor physics experiments or heat transfer measurements. There

7344-403: The reactor was down for three months because of the failure of one of the main cooling blowers. Some further delays were encountered because of offgas line plugging, but by the end of 1966 most of the startup problems were behind. During the next 15 months, the reactor was critical 80% of the time, with runs of 1, 3, and 6 months that were uninterrupted by a fuel drain. By March 1968,

7446-473: The reactor was shut down and final preparations made for power operation. Power ascension was delayed when vapors from oil that had leaked into the fuel pump were polymerized by the radioactive offgas and plugged gas filters and valves. Maximum power, which was limited to 7.4 MW th by the capability of the heat-rejection system, was reached in May ;1966. After two months of high-power operation,

7548-412: The result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed. In another example, excess Xe found in carbon dioxide well gases from New Mexico is believed to be from the decay of mantle -derived gases from soon after Earth's formation. After Neil Bartlett's discovery in 1962 that xenon can form chemical compounds,

7650-460: The salt. Removing the most significant neutron poison xenon-135 made the reactor safer and easier to restart. In solid-fuel reactors, on restart the Xe in the fuel absorbs neutrons , followed by a sudden jump in reactivity as the Xe is burned out. Conventional reactors may have to wait hours until xenon-135 decays after shutting down and not immediately restarting (so-called iodine pit ). Also in

7752-405: The same conditions, the density of solid xenon, 3.640 g/cm , is greater than the average density of granite , 2.75 g/cm . Under gigapascals of pressure , xenon forms a metallic phase. Solid xenon changes from Face-centered cubic (fcc) to hexagonal close packed (hcp) crystal phase under pressure and begins to turn metallic at about 140 GPa, with no noticeable volume change in

7854-533: The same time a program was launched to improve the resistance of Hastelloy-N to the embrittlement . An out-of- pile corrosion test program was carried out for Hastelloy-N, which indicated extremely low corrosion rates at MSRE conditions. Capsules exposed in the Materials Testing Reactor showed that salt fission power densities of more than 200 W/cm had no adverse effects on compatibility of fuel salt, Hastelloy-N, and graphite. Fluorine gas

7956-420: The solar gas cloud. In a similar way, xenon isotopic ratios such as Xe/ Xe and Xe/ Xe are a powerful tool for understanding planetary differentiation and early outgassing. For example, the atmosphere of Mars shows a xenon abundance similar to that of Earth (0.08 parts per million ) but Mars shows a greater abundance of Xe than the Earth or the Sun. Since this isotope is generated by radioactive decay,

8058-441: The stable isotopes of xenon , Xe and Xe (both stable isotopes with odd mass numbers), have non-zero intrinsic angular momenta ( nuclear spins , suitable for nuclear magnetic resonance ). The nuclear spins can be aligned beyond ordinary polarization levels by means of circularly polarized light and rubidium vapor. The resulting spin polarization of xenon nuclei can surpass 50% of its maximum possible value, greatly exceeding

8160-416: The starting points for the synthesis of almost all xenon compounds. The solid, crystalline difluoride XeF 2 is formed when a mixture of fluorine and xenon gases is exposed to ultraviolet light. The ultraviolet component of ordinary daylight is sufficient. Long-term heating of XeF 2 at high temperatures under an NiF 2 catalyst yields XeF 6 . Pyrolysis of XeF 6 in

8262-423: The successful operation of a commercial MSR: As of 2019, the MSRE is in a SAFESTOR state, meaning it still intact but shut down and actively monitored and maintained. After shutdown, the salt was believed to be in long-term safe storage. At low temperatures, radiolysis can free fluorine from the salt. As a countermeasure, the salt was annually reheated to about 302 °F (150 °C) until 1989. But beginning in

8364-423: The supernova and the time the meteorites had solidified and trapped the I. These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the Solar System , because the I isotope was likely generated shortly before the Solar System was formed, seeding the solar gas cloud with isotopes from a second source. This supernova source may also have caused collapse of

8466-460: The synthesis of xenon represents no energy gain for a star. Instead, xenon is formed during supernova explosions during the r-process , by the slow neutron-capture process ( s-process ) in red giant stars that have exhausted their core hydrogen and entered the asymptotic giant branch , and from radioactive decay, for example by beta decay of extinct iodine-129 and spontaneous fission of thorium , uranium , and plutonium . Xenon-135

8568-406: The thermal equilibrium value dictated by paramagnetic statistics (typically 0.001% of the maximum value at room temperature , even in the strongest magnets ). Such non-equilibrium alignment of spins is a temporary condition, and is called hyperpolarization . The process of hyperpolarizing the xenon is called optical pumping (although the process is different from pumping a laser ). Because

8670-458: The time that design stresses were set for the MSRE, the data that was available indicated that the strength and creep rate of Hastelloy-N were hardly affected by irradiation . After the construction was well along, the stress-rupture life and fracture strain were found to be drastically reduced by thermal neutron irradiation. The MSRE stresses were reanalyzed, and it was concluded that the reactor would have adequate life to reach its goals. At

8772-593: The two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate . Bartlett thought its composition to be Xe [PtF 6 ] , but later work revealed that it was probably a mixture of various xenon-containing salts. Since then, many other xenon compounds have been discovered, in addition to some compounds of the noble gases argon , krypton , and radon , including argon fluorohydride (HArF), krypton difluoride (KrF 2 ), and radon fluoride . By 1971, more than 80 xenon compounds were known. In November 1989, IBM scientists demonstrated

8874-569: The unit of power. In the electric power industry , megawatt electrical ( MWe or MW e ) refers by convention to the electric power produced by a generator, while megawatt thermal or thermal megawatt (MWt, MW t , or MWth, MW th ) refers to thermal power produced by the plant. For example, the Embalse nuclear power plant in Argentina uses a fission reactor to generate 2,109 MW t (i.e. heat), which creates steam to drive

8976-570: The unit within the existing system of practical units as "the power conveyed by a current of an Ampère through the difference of potential of a Volt". In October 1908, at the International Conference on Electric Units and Standards in London, so-called international definitions were established for practical electrical units. Siemens' definition was adopted as the international watt. (Also used: 1 A × 1 Ω.) The watt

9078-449: The xenon fluorides are well characterized, the other halides are not. Xenon dichloride , formed by the high-frequency irradiation of a mixture of xenon, fluorine, and silicon or carbon tetrachloride , is reported to be an endothermic, colorless, crystalline compound that decomposes into the elements at 80 °C. However, XeCl 2 may be merely a van der Waals molecule of weakly bound Xe atoms and Cl 2 molecules and not

9180-701: Was LiF-BeF 2 -ZrF 4 -UF 4 (65-29.1-5-0.9 mole %). The first fuel was 33% U; later a smaller amount of UF 4 was used. By 1960 a better understanding of fluoride salt based molten-salt reactors had emerged from earlier molten salt reactor research for the Aircraft Reactor Experiment . Fluoride salts are strongly ionic , and when melted they are stable at high temperatures, low pressures, and high radiation fluxes . Stability at low pressure permits less robust reactor vessels and increases reliability. The high reactivity of fluorine traps most fission reaction byproducts. It appeared that

9282-488: Was a pyrolytic graphite core. The fuel for the MSRE was LiF - BeF 2 - ZrF 4 - UF 4 (65-29.1-5-0.9 mole %). The secondary coolant was FLiBe (2LiF-BeF 2 ), and it operated as hot as 650 °C and operated for the equivalent of about 1.5 years of full power operation. The result promised to be a simple, reliable reactor. The purpose of the Molten-Salt Reactor Experiment

9384-475: Was completed in mid-1964. ORNL was responsible for quality assurance, planning, and management of construction. The primary systems were installed by ORNL personnel; subcontractors modified the building and installed ancillary systems. Hastelloy -N—a low chromium , nickel – molybdenum alloy—was used in the MSRE and proved compatible with the fluoride salts FLiBe and FLiNaK . All metal parts contacting salt were made of Hastelloy-N. The choice of Hastelloy-N for

9486-420: Was defined as equal to 10 units of power in the practical system of units. The "international units" were dominant from 1909 until 1948. After the 9th General Conference on Weights and Measures in 1948, the international watt was redefined from practical units to absolute units (i.e., using only length, mass, and time). Concretely, this meant that 1 watt was defined as the quantity of energy transferred in

9588-1528: Was emphasized by adding PuF 3 as makeup fuel during this period. After the final shutdown in December 1969, the reactor was left in standby for nearly a year. A limited examination program was then carried out, including a moderator bar from the core, a control rod thimble, heat exchanger tubes, parts from the fuel pump bowl, and a freeze valve that had developed a leak during the final reactor shutdown . The radioactive systems were then closed to await ultimate disposal. Parameters and operational statistics: Power : 8 MW (thermal) output: 92.8 GWh equivalent full-power: 11,555 h Fuel salt : fluoride cations : 65% Li-7 , 29.1% Be , 5% Zr , 0.9% U weight: 11,260 lbs (5,107 kg) melting temp: 813 F (434 C) inlet temp: 1175 F (635 C) outlet temp: 1225 F (663 C) flow rate: 400 gal/min (1514 l/min) fuel pump circulating: 19,405 h Coolant salt : fluoride cations: 66% Li-7, 34% Be weight: 15,300 lbs (6,940 kg) coolant pump circulating: 23,566 h Moderator : nuclear graphite Container : Hastelloy -N First fuel : U-235 first critical: 1 June 1965 thermal output: 72,441 MWh critical hours: 11,515 h full-power output equivalent: 9,006 h Second fuel : U-233 critical: 2 October 1968 thermal output: 20,363 MWh critical hours: 3,910 h full-power output equivalent: 2,549 h Shutdown : December 1969 The broadest and perhaps most important conclusion from

9690-402: Was enough latitude in the MSRE that deviations from predictions would not compromise safety or accomplishment of the objectives of the experimental reactor. Construction of the primary system components and alterations of the old Aircraft Reactor Experiment building (which had been partly remodeled for a proposed 60 MW th aircraft reactor) were started in 1962. Installation of the salt systems

9792-410: Was found to be produced by radiolysis of frozen salts, but only at temperatures below about 212 °F (100 °C). Components that were developed especially for the MSRE included flanges for 5-inch (130 mm) lines carrying molten salt, freeze valves (an air-cooled section where salt could be frozen and thawed), flexible control rods to operate in thimbles at 1,200 °F (649 °C), and

9894-521: Was in 1946 by American medical researcher John H. Lawrence, who experimented on mice. Xenon was first used as a surgical anesthetic in 1951 by American anesthesiologist Stuart C. Cullen, who successfully used it with two patients. Xenon and the other noble gases were for a long time considered to be completely chemically inert and not able to form compounds . However, while teaching at the University of British Columbia , Neil Bartlett discovered that

9996-549: Was loaded in 1964, and nuclear operation ended in December 1969, and all the objectives of the experiment were achieved during this period. Checkout and prenuclear tests included 1,000 hours of circulation of flush salt and fuel carrier salt. Nuclear testing of the MSRE began in June ;1965, with the addition of enriched U as UF 4 -LiF eutectic to the carrier salt to make the reactor critical . After zero-power experiments to measure rod worth and reactivity coefficients,

10098-398: Was reported in 2011 with a coordination number of four. XeO 2 forms when xenon tetrafluoride is poured over ice. Its crystal structure may allow it to replace silicon in silicate minerals. The XeOO cation has been identified by infrared spectroscopy in solid argon . Xenon does not react with oxygen directly; the trioxide is formed by the hydrolysis of XeF 6 : XeO 3

10200-520: Was the result of breeding from thorium in other reactors. Since this was an engineering test, the large, expensive breeding blanket of thorium salt was omitted in favor of neutron measurements. In the MSRE, the heat from the reactor core was shed via a cooling system using air blown over radiators . It is thought similar reactors could power high-efficiency heat engines such as closed-cycle gas turbines . The MSRE's piping, core vat and structural components were made from Hastelloy -N, and its moderator

10302-457: Was then added to the carrier salt, and in October 1968, the MSRE became the world's first reactor to operate on U. The U zero-power experiments and dynamics tests confirmed the predicted neutronic characteristics. An unexpected consequence of processing the salt was that its physical properties were altered slightly so that more than the usual amount of gas was entrained from the fuel pump into

10404-466: Was to demonstrate that some key features of the proposed molten-salt power reactors could be embodied in a practical reactor that could be operated safely and reliably and be maintained without excessive difficulty. For simplicity, it was to be a fairly small, one-fluid (i.e. non-breeding) reactor operating at 10 MW th or less, with heat rejection to the air via a secondary (fuel-free) salt. The pyrolytic graphite core, grade CGB, also served as

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