Showing papers on "Liquid metal published in 1978"

Method of generating energy by acoustically induced cavitation fusion and reactor therefor

Abstract: Two different cavitation fusion reactors (CFR's) are disclosed. Each comprises a chamber containing a liquid (host) metal such as lithium or an alloy thereof. Acoustical horns in the chamber walls operate to vary the ambient pressure in the liquid metal, creating therein small bubbles which are caused to grow to maximum sizes and then collapse violently in two steps. In the first stage the bubble contents remain at the temperature of the host liquid, but in the second stage the increasing speed of collapse causes an adiabatic compression of the bubble contents, and of the thin shell of liquid surrounding the bubble. Application of a positive pressure on the bubble accelerates this adiabatic stage, and causes the bubble to contract to smaller radius, thus increasing maximum temperatures and pressures reached within the bubble. At or near its minimum radius the bubble generates a very intense shock wave, creating high pressures and temperatures in the host liquid. These extremely high pressures and temperatures occur both within the bubbles and in the host liquid, and cause hydrogen isotopes in the bubbles and liquid to undergo thermonuclear reactions. In one type of CFR the thermonuclear reaction is generated by cavitation within the liquid metal itself, and in the other type the reaction takes place primarily within the bubbles. The fusion reactions generate energy that is absorbed as heat by the liquid metal, and this heat is removed from the liquid by conduction through the acoustical horns to an external heat exchanger, without any pumping of the liquid metal.

Electrohydrodynamic spraying to produce ultrafine particles

Abstract: Amorphous or microcrystalline alloy powder is prepared by the rapid quenching of ultrafine metallic spheroids generated from the molten metal state. The molten metal droplets are formed when an intense electric field (10 5 V/cm) is applied to the surface of liquid metal held in a suitable container. The interactions between the intense electric field and liquid surface tension disrupts the metal surface, resulting in a beam of positively charged droplets. The liquid metal spheres generated by this electrohydrodynamic process are subsequently cooled by radiative heat transfer. Rapid cooling of the droplets may be accomplished by heat transfer to a low pressure gas by free molecular heat conductivity. Quenching rates exceeding 10 6 °K./sec are possible using this technique. Thin film coatings are prepared by electrohydrodynamically spraying a beam of charged droplets against a target (substrate). The target can be electrically controlled to effect the charged particles impact. The materials to be sprayed electrodynamically can be varied in both throughput and species such that a target can have multimaterial layers being deposited coincidentally or sequentially. The ultra small droplet size will enhance the physical properties by reducing skin stresses and enhance the optical properties by reducing the growth of crystallites in the film. Precise layers can be deposited from extremely thin films to thick filters for optical characteristics into the infrared. All materials that can be molten and contained can be electrohydrodynamically sprayed and controlled for depositions upon a substrate material.

Determination of the density profile in the liquid–vapor interface near the triple point

Abstract: The density profile in the transition region between liquid and vapor Hg has been determined, at room temperature, from a study of the angular dependence of the reflection of Cr Kα x rays. This profile ρ (Z) has a hyperbolic tangent form with width L=5.6±0.5 A, where L≡−(ρL−ρG)[dρ (Z)/dZ]−1Z=0, with ρL and ρG the densities of liquid and vapor, respectively. The nature of the profile and the value of L are compared with the corresponding quantities obtained from computer simulations of the surface of liquid Ar. For liquid Hg, L is dominated by a static structural contribution fundamentally traceable to the nonzero wavelength of the electrons and their influence on the effective ion–ion potential. For liquid Ar, L is dominated by the contribution from thermal motion. The currently available theory of the liquid metal surface transition zone predicts a value for L which is too small by a factor of 2. This discrepancy, the role of surface capillary waves in broadening the transition zone, and the possible rel...

Thermal analysis of liquid--metal fast breeder reactors

Abstract: The book contains the following chapters: (1) general description of LMFBR systems, (2) reactor configurations and operating conditions, (3) thermal design criteria and analysis methods, (4) reactor hydrodynamics, (5) steady-state reactor heat transfer, (6) transient reactor heat transfer, and (7) heat exchangers in LMFBR reactors. (DG)

Experimental determination of critical data of liquid molybdenum

Abstract: The submicrosecond resistive pulse heating of wire-shaped metallic samples in a highly incompressible medium leads to a thermodynamic state very close to the critical point of the liquid metal. The additional application of a static pressure may result in a critical or supercritical transition. First results on the critical data of molybdenum are reported: Tc=(11150+or-550)K, pc=(5460+or-1160) bar, nu c=(36.5+or-3.5) cm3 mol-1.

Prediction of electron beam welding spiking tendency

Abstract: On the basis of measured temperature distributions in electron beam welding cavities it is shown that the vapor pressure force dominates in the lower region and the surface tension in the upper region. The region where these two forces are approximately equal is unstable and the surface tension force causes inward flow of liquid metal which tends to form a projection. For a specific material this projection location was found to depend on cavity depth. By postulating that the formation of liquid metal projections at this location results in cavity instabilities, a physical model for predicting when spiking would occur was purposed. A procedure then developed for determining the spiking tendency for a specified material and set of weld parameters is described.

Process for joining metals

Abstract: A method is disclosed for joining two or more pieces of metal along a seam line by directing a jet of liquid metal onto the seam, the surfaces of which, at the seam region of the metals to be joined, have been pre-melted just before the liquid metal jet is poured on, the pre-melting being done by an energy carrying beam of radiation, e.g. an electron beam or a laser beam, of high power density, a mixture of molten metals thus being formed which thereafter will cool, solidify, and thereby join the various metal pieces into a single welded structure. By making the power and power density of the radiation beam used for pre-melting sufficiently high, only a thin surface layer is melted rapidly; it will adhere to the underlying solid interface by natural adhesion. On account of the rapidity of the melting only a minimum of the beam energy is lost by heat conduction. No beam energy is used up for melting the liquid metal jet; the latter also acts as filler for any size of gap in the seam area. Thus, the energy for the melt coming from two different sources, not only from the radiation beam, this joining process is faster than conventional electron beam or laser beam welding and it can accommodate larger joint gaps. The same process can be used to clad a pre-melted metal surface by a thin layer of another metal supplied by the liquid metal jet.

Experimental investigations of trace element fractionation in iron meteorites. I - Early results

Abstract: Experimental procedures for measuring trace element partitioning among metal and sulfide and silicate phases are described, and solid metal/liquid metal partition coefficients for minor and trace elements in the Fe-Ni system at 5 to 14% Ni are reported. The bulk compositions desired are homogenized at superliquidus temperature for 15-24 hours, held at a temperature in the solid/liquid two phase region for about 24 hours, and quenched to freeze in the equilibrium compositions. Run products are analyzed by electron microprobe. With the exception of Cr, all preliminary partition coefficients obtained are in the same sense as values derived from iron meteorites. The partition coefficients for Cr in solid metal/liquid metal and metal/troilite systems suggest that IIIAB and main group pallasites equilibrated with 9-22% troilite. A second method which makes it possible to place upper and lower limits on the partition coefficient by holding part of the sample at subliquidus and part at superliquidus temperatures, yielded significantly different results for the two metals tested (Au and Pt) from those obtained by the first method, demonstrating the importance of a close approach to equilibrium before using experimentally-determined partition coefficients to test empirical differentiation models for iron meteorites.

Performance investigations of liquid-metal heat pipes for space and terrestrial applications

Abstract: The high heat transfer capacity of liquid-metal heat pipes is demonstrated in performance tests with mercury, potassium, sodium, and lithium working fluids and wick structures which serve to minimize liquid pressure losses and vapor/liquid interactions. Appropriate wicks for horizontal and vertical operation are described. It is shown that heat-transfer with these wicks is limited by vapor flow effects. Examples are given of particular effects associated with a long adiabatic section between evaporator and condenser and with a heat source of uniform temperature as opposed to a source of uniform power.

Application of Rapidly Solidified Alloys.

Abstract: : This program is being conducted for the purpose of applying the principle of rapid solidification of aluminum and iron alloy powders and subsequent development of stronger alloy compositions for fan blade application (Al alloys) and higher speed bearing material (Fe alloys). Centrifugal atomization and forced convective cooling are being used to produce the fast-cooled powder. During this report period, adaptation of the RSR (Rapid Solidification Rate) process to aluminum and iron systems was continued. Both Al and Fe alloys were produced and consolidated by direct extrusion. Hardness and mechanical testing were begun for initial evaluation of aluminum alloys. This program has demonstrated that controlled, rapid solidification can lead to a microcrystalline form, a condition which could possibly point the way to alloy homogeneity never before considered possible. It has also shown that a central rotary source can be used for liquid metal atomization into powder particles of sizes commensurate with average particle cooling rates of 100,000-1,000,000 K/sec. The specific objectives of this effort are the development of an improved aluminum alloy suitable for V/STOL-A fan blades and an improved iron alloy suitable for rolling element bearings for advanced aircraft powerplants. Originator supplied keywords include: Powder metallurgy.

Shape of Two-Dimensional Solidification Interface During Directional Solidification by Continuous Casting

Abstract: An analysis was made of the two-dimensional solidification of an ingot being cooled and withdrawn vertically downward from a mold consisting of parallel walls of finite length. Heat transfer analysis shows how the flatness of the interface is related to the ingot thickness, the withdrawal rate, the heat addition from the superheated liquid metal, and the temperature difference available for cooling. This provides an understanding of the conditions that will yield a maximum rate of casting while achieving the desired flatness of the interface. The results are interpreted with respect to the conditions for obtaining an aligned eutectic structure by directional solidification. In this process an additional constraint must be included that relates the ingot withdrawal rate and the heat transfer rate from the liquid metal to the solidification interface.

A Model of Liquid Metal Droplet Vaporization in Arc Heated Gas Streams

Abstract: A model of simultaneous heat and mass transfer has been constructed to describe vaporization of liquid metal droplets in arc heated gas streams. The major assumptions of the model include 1) plug flow, 2) negligible pressure drop, 3) no droplet-droplet interactions, 4) negligible gas radiation, natural convection, thermal diffusion, diffusion-thermo transport and axial conduction and diffusion, and 5) no interfacial discontinuities in temperature or concentration. The latter assumption is discussed in detail in a separate appendix. The analysis is limited to binary, nonreacting gas mixtures. The mathematical formulation results in five nonlinear, first order differential equations with temperature and compositional dependent properties. The model is applied to the vaporization of sodium and magnesium droplets injected into arc heated argon flowing in a cylindrical reactor. The effect of parameters such as initial droplet radius, reactor diameter, and liquid metal flowrate on the reactor length required to achieve a specified degree of vaporization is calculated.

Apparatus for the purification of a liquid metal for cooling in the core of a fast neutron reactor

Abstract: Apparatus for the purification of the liquid metal for cooling the core of a fast neutron reactor comprising a heat insulating envelope immersed in the reactor core and suspended from the protective slab surmounting the latter, a removable plug disposed in said slab and giving access to the upper part of the inside of the envelope and, within the latter, a cooling coil for cooling a liquid metal flow taken from the reactor core to a temperature which ensures the solidification of impurities, a filter cartridge for filtering the cooled liquid metal, a heat exchanger for the at least partial heating of the purified metal prior to its return to the reactor core and a valve for regulating the purified metal flow returned to the core, wherein it comprises a passage for returning to the upper part of the envelope purified metal from the filter cartridge, the purified metal being returned to the reactor core with the purified metal in heat exchange with the metal to be purified in a regulated flow, the regulating valve of said flow being disposed in the upper part of the envelope.

Device for the thermal protection of an internal structure of a liquid metal cooled fast reactor

Abstract: The fast reactor structure to be protected comprises a wall and a parallel cylindrical shell having a free top edge which forms an overflow sill. A diverted flow of liquid metal withdrawn from a principal volume is circulated upwards through a vertical space formed between the wall and the shell. The shell surface which is remote from the space is provided with a packing of heat-insulating elements so that the overflowing sheet of liquid metal which falls on the downstream side of the overflow sill passes through the packing before returning into the principal volume of liquid metal.

Circulating pumps of a liquid metal, generally sodium, ensuring the cooling of the core of a fast neutron reactor

Abstract: A circulating pump, particularly for the liquid cooling metal of the core of a fast neutron reactor, comprising a non-removable assembly permanently disposed in the vessel containing the liquid metal, constituted by a suction channel, a diffuser and at least one delivery pipe, wherein the non-removable assembly is suspended on a supporting structure which is immobilized relative to the core.

Local and Instantaneous Measurements in Liquid Metal MHD

Abstract: In liquid metals used for laboratory experiments in magneto-hydrodynamics, such as mercury, the techniques of local and instantaneous measurements are known to be much more delicate than in classical fluids like water and air. Whatever diagnostic method is used, two categories of difficulties must be overcome: those due to the presence of a magnetic field and those due to the nature of the fluid. The former generally appear as fundamental difficulties, since the magnetic field acts like a new parameter which modifies the physics of the measurement apparatus; we will see further on that this can be put to use for imagining new methods which have no equivalent in classical hydrodynamics. The latter appear rather like secondary disturbances which would not exist in perfect experiments and which can (at least theoretically) be reduced by the care taken by the experimenter.

The Diffusivity of Oxygen in Liquid Copper-Lead Alloys

Abstract: The oxygen diffusivity in liquid copper-lead alloys at 1403 K (1130° C) was measured using the electrochemical cell: Ni−NiO/ZrO2(+CaO)/O in liquid Cu−Pb alloy(I)/ZrO2(+CaO)/O in liquid Cu−Pb alloy (II). Oxygen in liquid Cu−Pb alloy (I) was transferred to the right by applying a preselected voltage between the two liquid Cu−Pb alloys. The oxygen diffusivity in liquid Cu−Pb alloy(I) was calculated from the emf change with time between the Ni−NiO and liquid Cu−Pb alloy (I) electrodes. The results were: Open image in new window It was found that the oxygen diffusivity in liquid copper-lead alloys did not change drastically over the entire composition range, in contrast with that reported by other investigators for liquid copper-nickel alloys. The oxygen diffusivity in pure liquid lead agreed with the results of our previous work using an FeO−Fe3O4 mixture as a sink for oxygen.

Process for the delivery of molten metal to a caterpillar type mold

Abstract: A process is described for the delivery of molten metal to a caterpillar type mold which is inclined slightly to the horizontal and is used for casting wide strip, especially non-ferromagnetic metals, such as aluminium of aluminium alloys. The metal is fed through a delivery nozzle made of fire resistant material to a head of liquid metal in the mold either under the free surface of this head of metal or through this free surface on the head of liquid metal. Premature contact with the mold wall is avoided and the molten metal is fed in an almost pressureless manner.

Safety operation of liquid metal cooling fast reactor

Abstract: PURPOSE:To improve an activity rate, a reliability, and an economical efficiency by performing heat exchange between the lst cooling system and steam system, where a liquid metal is circulating, by means of a stable material which is reacting with neither liquid metal nor water.

Arc heater with silicon lined reactor

Abstract: An arc heater system for producing high purity silicon characterized by the use of an arc heater into which a silicon halide is injected together with a liquid metal reductant, such as an alkali metal, which are reacted together by projecting them into a reaction chamber to cause the formation of liquid silicon, and the walls containing the system being provided with cooling jacket means for preliminarily heating the reactants.

Method and apparatus for liquid metal circulation in an acyclic machine

Abstract: A constant supply of liquid metal for current collectors in a disk-type acyclic machine is provided by passageways through each stator disk extending from the region adjacent a radially-outer collector to the region adjacent a radially-inner collector. Dynamic pumping of the liquid metal in the region adjacent the outer current collectors is provided by the rotational motion of the rotor disks and by Lorentz expulsion forces acting upon the liquid metal. The openings to said passageways in the region of the outer current collectors are configured to catch a portion of the liquid metal moving with the radially-outer edge of the rotor disks and thereby apply the dynamic pressure of this portion of the liquid metal to move the liquid metal radially-inwardly. Return flow is accommodated by flow paths in the stator separate from those provided for inward flow.

Apparatus for use in a liquid alkali metal environment

Abstract: Heat exchange apparatus for use in a liquid metal environment comprising heat exchange tubes and grid plates having complementary bearing surfaces. The tubes are of stainless steel and the complementary bearing surfaces of the grids are aluminized to reduce wear and friction.

Offset liquid metal storage method and means

Abstract: An offset or asymmetrical self-contained liquid metal current collector forcyclic or homopolar electrical generators or motors is provided which includes a narrow annular volume on one side and a wide annular volume on the other side of the collector disc. Selectively positioned circular troughs effectively communicate with each other so that the liquid metal is trapped and retained when the rotating speed of the disc is too low to centrifugally maintain the liquid metal at the outer periphery of the disc.

Heat transport system in use of liquid metal

Abstract: PURPOSE:To facilitate smooth transport from forced cooling mode to heat removal mode by means of natural circulation at the time of electric power source loss during the action in an auxiliary core cooling system in a heat transport system for auxiliary core cooling in a fast neutron reactor.

Nuclear reactor with equipment for preventing convection of metal vapors

Abstract: A liquid metal-cooled nuclear reactor has a reactor vessel with a cover at the top thereof and is partly filled with liquid metal up to a given surface level, the liquid metal surface and the reactor-vessel cover defining therebetween a gas-filled space, at least one quasi-tight convection barrier being disposed in the space and subdividing it in elevation.