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37-523: The ARE was the first reactor to use circulating molten salt fuel. The hundreds of engineers and scientists working on ARE provided technical data, facilities, equipment, and experience that enabled the broader development of molten-salt reactors as well as liquid metal cooled reactors . The concept of nuclear-powered aircraft was first formally studied in May 1946 by the US Army Air Forces . It

74-412: A class of ionic liquids. As a reference, molten sodium chloride , table salt has a melting point (m.p.) of 801 °C (1,474 °F). A variety of eutectic mixtures have been developed with lower melting points: Alkali metal nitrates are relatively low melting and thermally stable. The least stable, LiNO 3 (m.p. 255 °C (491 °F)) decomposes only at 474 °C (885 °F). At

111-414: A jet were used to bring the pits to sub-atmospheric pressure for the rest of the experiment. The safety radiation detectors shut down the reactor a few times during restart and were withdrawn to be further away from the reactor. Eventually, the reactor started back up and reached high power. On November 12, operation of the reactor was demonstrated to Air Force and ANP personnel who had gathered at ORNL for

148-504: A painstaking and careful process of adding the enriched fuel. Much of the four days was spent removing plugs and repairing leaks in the enrichment line. A series of fuel samples were taken periodically. Most notably, they showed an increase in chromium content at a rate of 50 ppm/day, indicating rapid corrosion of the fuel pipes. A series of experiments were performed in the ARE supporting its mission. At 4:19 p.m. on November 8, during

185-406: A quarterly information meeting. Load following was demonstrated by turning the blowers on and off. With all operational objectives attained, the decision to cease operation was made. Colonel Clyde D. Gasser was visiting the lab at this time and was invited to officiate the termination of the experiment. At 8:04 p.m., he scrammed the reactor for the last time. Much information was published about

222-483: A reactor for flight. Originally, the ARE was conceived as a liquid sodium metal-cooled beryllium oxide (BeO)-moderated solid-fuel reactor. The BeO moderator blocks were purchased with the solid-fuel design in mind. However, concerns regarding chain reaction stability related to xenon in solid fuel at very high temperatures were serious enough to warrant abandoning solid fuel and replacing it with circulating fluid fuel. A fluid-fueled option with molten fluoride salt

259-543: A second body, usually a compact object ( white dwarf , neutron star or black hole ), and is eventually accreted onto it. It is a common phenomenon in binary systems , and may play an important role in some types of supernovae and pulsars . Mass transfer finds extensive application in chemical engineering problems. It is used in reaction engineering, separations engineering, heat transfer engineering, and many other sub-disciplines of chemical engineering like electrochemical engineering. The driving force for mass transfer

296-594: A type of nuclear reactor that uses molten salt(s) as a coolant or as a solvent in which the fissile material is dissolved. Experimental salts using lithium can be formed that have a melting point of 116 °C while still having a heat capacity of 1.54 J/(g·K). Molten chloride salt mixtures are commonly used as quenching baths for various alloy heat treatments , such as annealing and martempering of steel . Cyanide and chloride salt mixtures are used for surface modification of alloys such as carburizing and nitrocarburizing of steel. Cryolite (a fluoride salt)

333-608: Is commonly used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems . Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere , the purification of blood in the kidneys and liver , and the distillation of alcohol. In industrial processes, mass transfer operations include separation of chemical components in distillation columns, absorbers such as scrubbers or stripping, adsorbers such as activated carbon beds, and liquid-liquid extraction . Mass transfer

370-463: Is often coupled to additional transport processes , for instance in industrial cooling towers . These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with air. The water is cooled by expelling some of its content in the form of water vapour. In astrophysics , mass transfer is the process by which matter gravitationally bound to a body, usually a star , fills its Roche lobe and becomes gravitationally bound to

407-481: Is produced from aluminium oxides by electrolysis of a molten mixture of sodium hexafluoroaluminate and alumina at 950 °C (1,740 °F). This conversion is called the Hall-Haroult process . Molten salts (fluoride, chloride, and nitrate ) can be used as heat transfer fluids as well as for thermal storage . This thermal storage is used in concentrated solar power plants. Molten-salt reactors are

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444-740: Is used as a solvent for aluminium oxide in the production of aluminium in the Hall-Héroult process . Fluoride, chloride, and hydroxide salts can be used as solvents in pyroprocessing of nuclear fuel . Ambient-temperature molten salts (also known as ionic liquids ) are present in the liquid phase at standard conditions for temperature and pressure . Examples of such salts include N -ethylpyridinium bromide and aluminium chloride mix, discovered in 1951, and ethylammonium nitrate discovered by Paul Walden . Other ionic liquids take advantage of asymmetrical quaternary ammonium cations like alkylated imidazolium ions, and large, branched anions like

481-492: Is usually a difference in chemical potential , when it can be defined, though other thermodynamic gradients may couple to the flow of mass and drive it as well. A chemical species moves from areas of high chemical potential to areas of low chemical potential. Thus, the maximum theoretical extent of a given mass transfer is typically determined by the point at which the chemical potential is uniform. For single phase-systems, this usually translates to uniform concentration throughout

518-438: The bistriflimide ion. Mass transfer Mass transfer is the net movement of mass from one location (usually meaning stream, phase , fraction, or component) to another. Mass transfer occurs in many processes, such as absorption , evaporation , drying , precipitation , membrane filtration , and distillation . Mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase

555-471: The ANP project decided that technical information and experience needed to support the objective of nuclear-powered flight could most economically be obtained from building and operating the ARE. They considered the task of flying a supersonic airplane on nuclear energy exceedingly complex and thought more than one experimental reactor may be necessary before sufficient information was obtained to design and construct

592-450: The ARE operated, the ANP project moved on with plans to build a larger experiment, the 60 MW Aircraft Reactor Test (ART). The ART was to be a NaF-ZrF 4 -UF 4 -fueled, Be-moderated, Be-reflected core with sodium metal as the reflector coolant and NaK as the secondary coolant, with shield made of lead and borated water. Building 7503 at ORNL was significantly re-excavated in an extension project including new deep excavations to accommodate

629-598: The ART, but the program was cancelled before the new experiment was performed. The building and facilities later went on to house the Molten-Salt Reactor Experiment . Molten salt Molten salt is salt which is solid at standard temperature and pressure but liquified due to elevated temperature. A salt that is liquid even at standard temperature and pressure is usually called a room-temperature ionic liquid , and molten salts are technically

666-483: The analogy between mass and heat transfer and momentum transfer becomes less useful due to the nonlinearity of the Navier-Stokes equation (or more fundamentally, the general momentum conservation equation ), but the analogy between heat and mass transfer remains good. A great deal of effort has been devoted to developing analogies among these three transport processes so as to allow prediction of one from any of

703-483: The ascent to high power, the reactor was shut down following high airborne radioactivity measurements in the basement. It appeared that the gas fittings to the main fuel pump were leaking fission-product gases and vapors into the pits, and the pits were leaking into the basement through defective seals in some electrical junction panels. A 2 in (5 cm) pipeline was run from the pits 1,000 ft (300 m) south into an uninhabited valley. Portable compressors and

740-399: The commonly used approximate differential equations for momentum, heat, and mass transfer. The molecular transfer equations of Newton's law for fluid momentum at low Reynolds number ( Stokes flow ), Fourier's law for heat, and Fick's law for mass are very similar, since they are all linear approximations to transport of conserved quantities in a flow field. At higher Reynolds number,

777-457: The flow patterns within the system and the diffusivities of the species in each phase. This rate can be quantified through the calculation and application of mass transfer coefficients for an overall process. These mass transfer coefficients are typically published in terms of dimensionless numbers , often including Péclet numbers , Reynolds numbers , Sherwood numbers , and Schmidt numbers , among others. There are notable similarities in

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814-429: The fuel systems. Water lines were cut first. Then, sodium lines were cut with hack saws and immediately sealed with several layers of masking tape. The sodium pump was cleaned and the impeller was removed for examination. When the sodium pump and heat exchanger were removed, the radiation field in the room increased to 600 mrem /hr. The equipment had been shielding the area from the fuel system radiation. The fuel system

851-440: The full power level of 3 MW. The design fuel temperature was 1,500 °F (820 °C), with a 350 °F (180 °C) temperature rise across the core, though the peak temperature reached 1,580 °F (860 °C) in steady operation and peaked at 1,620 °F (882 °C) in transients. 46 US gal (170 L) of fuel flowed through the reactor per minute at a core pressure of about 40 psi (2.8 bar). Sodium

888-412: The operation of the reactor, including detailed experimental logs, power traces, and 33 lessons learned. Between shutdown and fuel dumping, the operating personnel were required to wear gas masks because of the high level of airborne radioactivity, which was caused by an offgas leak which could not be located. On November 13, the fuel was transferred to the fuel dump tank. Pressurized carrier salt flushed

925-412: The other extreme, cesium nitrate melts at 414 °C (777 °F) and decomposes at 584 °C. Molten salts have a variety of uses. One industrial application is the production of magnesium, which begins with production of magnesium chloride by chlorination of magnesium oxide : Electrolysis of the resulting molten magnesium chloride is conducted at 700 °C (1,292 °F): Aluminium metal

962-437: The phase, while for multiphase systems chemical species will often prefer one phase over the others and reach a uniform chemical potential only when most of the chemical species has been absorbed into the preferred phase, as in liquid-liquid extraction . While thermodynamic equilibrium determines the theoretical extent of a given mass transfer operation, the actual rate of mass transfer will depend on additional factors including

999-448: The pipes and diluted the dump tank. Flush salt was heated to 100 °F (38 °C) above the system temperature and pumped through the fuel channels. Operators observed the thermocouples to ensure flush salt flowed in all channels. Two flat 6 ft (1.8 m) by 4 ft (1.2 m) lead shields with 2 in (5.1 cm) thickness were suspended in the heat exchanger cell to protect decommissioning personnel from radiation from

1036-802: The reactor and dump tank chambers. The ambitious goals and military importance of the ANP catalyzed a significant amount of research and development of complex systems in challenging high-temperature, high- radiation environments. Corrosion and hot sodium handing studies began in 1950. Investigations of the engineering and fabrication problems involved in handling molten fluoride salts began in 1951 and continued through 1954. Natural-convection corrosion test loops were operated to down-select suitable material and fuel combinations. Subsequent studies in forced-circulation test loops established means to minimize corrosion and mass transfer . Development of pumps, heat exchangers , valves , pressure instrumentation , and cold traps spanned from late 1951 to summer 1954. Much of

1073-475: The test facility building began in July 1951. The ARE was operated successfully. It became critical with a mass of 32.8 lb (14.9 kg) uranium-235 . It was very stable as a result of its strong negative fuel temperature coefficient (measured at -9.8e-5 dk/k/°F). The assembly was first sufficiently assembled on August 1, 1954, at which point a three-shift operation commenced for tests. Hot sodium metal

1110-593: The work was based on extensive experience at lower temperature from Argonne National Laboratory and the Knolls Atomic Power Laboratory . Techniques had to be developed concerning the construction, preheating, instrumentation, and insulation of reliable leak-tight high-temperature circuits made of Inconel . They found that all-welded construction was necessary. In all, equipment development in support of high-temperature leak-tight operation lasted about four years. The ARE Hazards Summary Report

1147-628: Was carefully dismantled starting in February 1955. The main fuel pump bowl surveyed at 900 mrem/hr at 5 ft (2 m). A portable grinder that could be operated from within a lead box was built to cut the fuel lines near the reactor can. Once it was free, the reactor was moved to storage and later to a burial ground. The fuel in the dump tank was slated to be reprocessed. About 60 samples of equipment and material were taken for detailed analysis and examination. Metallographic, activation , visual, stereophotographic , and leak tests were performed. After

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1184-415: Was flowed through the system beginning on September 26 to test the process equipment and instrumentation. Problems with the sodium vent and sodium purification systems required lengthy repairs. After several sodium dumps and recharges, carrier salt was introduced to the system on October 25. Fuel was first added to the reactor on October 30. Initial criticality was reached at 3:45 p.m. on November 3, after

1221-717: Was hypothesized that the unique characteristics of nuclear power could be applied to long-range supersonic flight, which was considered highly valuable in terms of military strategy. Challenges in the proposal were understood immediately, and by 1950 the Atomic Energy Commission joined with the Air Force to study the possibilities via technology development in the Aircraft Nuclear Propulsion (ANP) program which ran from 1946 (originally as USAF NEPA) until cancelled in 1961. The ORNL staff of

1258-414: Was instrumented with two fission chambers , two compensated ionization chambers , and 800 thermocouples . The ARE control system could automatically scram the reactor based on high neutron flux , fast reactor period , high reactor exit fuel temperature, low heat exchanger fuel temperature, low fuel flow rate, and loss of offsite power. The heat exchanger chamber took up significantly more space than

1295-410: Was issued on November 24, 1952. A low-temperature critical mockup of the reactor was assembled to verify the calculation models. The BeO moderator blocks were fitted with straight tubes filled with a powder mixture to simulate the fuel. Critical mass, regulating rod worth, safety rod worth, neutron flux distributions, and reactivity coefficients of a wide variety of materials were measured. Construction of

1332-558: Was pumped through the reactor at a rate of 150 US gal (570 L) per minute with about 50 psi (3.4 bar) of pressure. The fuel salt transferred heat to a helium loop, which then transferred the heat to water. Additionally, the reflector and moderator blocks were cooled with a liquid sodium metal cooling loop, which also transferred heat to helium and then water. The reactor contained one neutron source (15 curies of polonium-beryllium), one regulating rod, and three helium-cooled boron carbide shim rods. The experiment

1369-482: Was worked into the original design. The ARE was designed to be a prototype of a 350-megawatt, BeO-moderated, circulating-fuel aircraft reactor. It used a fuel composed of 53.09 mole % NaF, 40.73 mole % ZrF 4 , and 6.18 mole % UF 4 . The reactor was a BeO cylinder with bent tubes directing flowing fuel through the core in both directions. It was surrounded by an Inconel shell. The ARE operational life targeted 1,000 hours, with as much time as possible at

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