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Estimation Method for Residual Sodium Amount on Unloaded Dummy Fuel Assembly
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The withdrawal of a liquid or the translation of a liquid slug in a capillary tube leads to the deposition of a thin film on the inner wall. When particles or contaminants are present in the liquid, they deposit and contaminate the tube if the liquid film is sufficiently thick. In this article, we experimentally investigate the condition under which particles are deposited during the air invasion in a capillary tube initially filled with a dilute suspension. We show that the entrainment of particles in the film is controlled by the ratio of the particle and the tube radii and the capillary number associated with the front velocity. We also develop a model which suggests optimal operating conditions to avoid contamination during the withdrawal of a suspension from a tube. This deposition mechanism can also be leveraged in coating processes by controlling the deposition of particles on the inner walls of channels.
A surface coated with organic molecules has been probed by a sub 100 nm resolution particulate sensor by surface-enhanced Raman scattering (SERS) technique. The spatial distribution of those molecules formed on the solid surface was altered by a dip-coating method as a function of a substrate-lifting rate. Isolated silver nanoparticles ([similar]50 nm) as “antenna” particles were deposited from the gas phase onto the surface by means of an electrostatic-assisted spray. The surface with the particles was analyzed with Raman spectroscopy technique. These analyses provide spatial information on the molecules over the surface, when SERS spectra of the molecules obtained from each measurement point are converted into the position of molecules. The occurrence frequency of SERS is found to be correlated with the two-third power law of the lifting rate which is proportional to a mass concentration of molecules per unit area, whereas the average Raman intensity is independent.
We are interested in the amount of fluid left behind a drop moved inside a capillary tube. Long ago, Taylor showed that for very viscous liquids moved at small velocities, the film thickness is a monotonic increasing function of the capillary number. New data obtained with liquids of low viscosity are reported here and compared with Taylor's law. Two successive effects are observed: above a threshold in capillary number, the film is thicker than a Taylor film; at a very high speed, the deposition law becomes a decreasing function of the drop velocity. Both behaviors are analyzed thanks to scaling arguments and shown to be consequences of inertia.
Sodium wetting experiments were performed to investigate the reactive wetting of metallic plating materials by liquid sodium at 250 C for the ultrasonic sensor of the under-sodium viewer. SUS304 stainless steel specimens were electrolytically plated with four metallic materials (nickel, palladium, gold, and indium) that have different solubilities in sodium, and the spreading velocity of sodium droplets on the metallic plated specimens was measured. It was confirmed that the spreading velocity increased as the solubility increased, and the constant on the spreading velocity on the plated specimens was unique for the plating materials and was proportional to the logarithm of the solubility of the plating materials. Furthermore, it is considered possible to select plating materials based on solubility from the result of this study.
We consider the deposition of a film of viscous liquid on a flat plate being withdrawn from a bath, experimentally and theoretically. For any plate speed U, there is a range of "thick" film solutions whose thickness scales like U{1/2} for small U. These solutions are realized for a partially wetting liquid, while for a perfectly wetting liquid the classical Landau-Levich-Derjaguin film is observed, whose thickness scales like U{2/3}. The thick film is distinguished from the Landau-Levich-Derjaguin film by a dip in its spatial profile at the transition to the bath. We calculate the phase diagram for the existence of stationary film solutions as well as the film profiles and find excellent agreement with experiment.
This study aims to control the wettability of pure transition metals by liquid sodium or liquid tin. Such wettability was evaluated by measuring the contact angles with the droplet method. Pure titanium, iron, nickel, copper, and molybdenum metals were selected as specimens in this experiment. All experiments were conducted in an environment with high pure argon gas and extremely low moisture to avoid the influence of oxygen on the liquid metals. The measurement temperature was just above the melting temperature of each liquid metal. Results showed that in both liquid sodium and liquid tin, the measured contact angle changed depending on the atomic number of the substrate metal. The electronic structure of the interface between a liquid metal and a substrate metal was calculated by the molecular orbital method. Simple cluster models of the interface between the liquid metal and substrate transition metal were used in this calculation. The calculation results confirmed that the electronic state of the interface was expressed well. The magnitude of the atomic bonding between the liquid metal and substrate metal changed in accordance with the atomic number of the substrate metal, and the magnitude of the atomic bonding between the substrate metals changed similarly. There was an evident relationship between the atomic bonding ratio and the contact angle. The atomic bonding ratio is the ratio of the liquid-metal-substrate metal-atomic bonding to the substrate metal atomic bonding. This finding implies that the atomic bonding affected the wettability between the liquid metal and the substrate metal. The atomic bonding was obtained as one of the indications was obtained to control the wettability by liquid metal.
This Paper was Originally Published in Japanese in J. Japan Inst. Met Mater. 85 (2021) 110–119.
Fig. 16 Relationship between contact angle and bond order Ratio (Centered M-LM/Centered M-1st. Neighbor M) of (a) liquid sodium and (b) liquid tin. Fullsize Image
Wettability of pure transition metals with liquid sodium or liquid tin has been evaluated using a contact angle droplet method. Titanium, iron, nickel, copper and molybdenum pure metals were selected as specimens in this experiment. All experiments were carried out in high purity argon gas and extremely low moisture to avoid influence of oxygen to liquid metal. Measurement temperature was set just above the melting temperature of each liquid metal. As a result, for both liquid sodium and liquid tin, the measured contact angle changed depending on the atomic number of substrate metals. An electronic structure of the interface between liquid metal and substrate metal was calculated by the molecular orbital method. Simple cluster models of the interface between liquid metal and substrate transition metals were used in this calculation. It was found that the calculation results well express an electronic state of interface. The atomic bonding between liquid metal atom and substrate metal atom changed depending on the kind of substrate metal. Also, the atomic bonding between substrate metal atoms changed similarly. It became clear that there was a reasonable relationship between an atomic bonding ratio and the contact angle. It clearly suggested the atomic bonding affected wettability between liquid metal and substrate metal. The atomic bonding was obtained as one of indications to reveal the wettability by transition metals with liquid metals.
Fig. 16 Relationship between contact angle and bond order Ratio (Centered M-LM / Centered M-1st. Neighbor M) of (a) liquid sodium and (b) liquid tin. Fullsize Image
In a fuel handling system of sodium-cooled fast reactors (SFRs), it is necessary to remove the sodium remaining on spent fuel assemblies (FAs) before storing them in a spent fuel water pool (SFP). A next-generation SFR in Japan has adopted an advanced dry-cleaning system that consists of argon gas blowing to remove the metallic residual sodium on the FA, which increases economic competitiveness and reduces waste products thanks to a waterless process. In this R&D work, the performance of the dry cleaning process has been investigated.
This paper describes experimental and analytical studies focusing on the amount of residual sodium remaining on a fuel pin bundle before and after the argon gas blowing process. The experiments were conducted using a sodium test loop and a short (approximately 1 m) specimen consisting of a 7-pin bundle. The effects of the blowing gas velocity and the blowing time were quantitatively analyzed in the experiments. The blowing gas velocity was varied from 3.9 to 31.3 m/s, and 113 data-points of the residual sodium were collected during the experiment. On the basis of these experimental results, the residual sodium quantification method for the fuel pin bundle was constructed.
In a fuel handling system of sodium-cooled fast reactors (SFRs), it is necessary to remove the sodium remaining on spent fuel assemblies (FAs) before storing them in a spent fuel water pool (SFP). A next-generation SFR in Japan has adopted an advanced dry cleaning process which consists of argon gas blowing to remove the metallic residual sodium on the FA, which increases economic competitiveness and reduces waste products thanks to a waterless process. In this R&D work, performance of the dry cleaning process has been investigated. This paper describes experimental and analytical work focusing on the amount of residual sodium remaining on FA components, for instance the handling head, the wrapper tube, the upper shielding, and the entrance nozzle. The tests, using water and sodium, investigated the amount of residual liquid remaining on laboratory scale specimens representing three fundamental shapes: narrow gaps, horizontal holes, and corners. On the basis of the experimental results, the residual sodium quantification method for FA was constructed. The constructed method enables quantitative estimation of the amount of residual sodium on the entire FA before and after the argon gas blowing with 95% reliability.
A solid withdrawn from a liquid bath entrains a film. In this review, after recalling the predictions and results for pure Newtonian liquids coated on simple solids, we analyze the deviations to this ideal case exploring successively three potential sources of complexity: the liquid-air interface, the bulk rheological properties of the liquid and the mechanical or chemical properties of the solid. For these different complexities, we show that significant effects on the film thickness are observed experimentally and we summarize the theoretical analysis presented in the literature, which attempt to rationalize these measurements.
We investigate the entrainment of liquid films on a partially wetting plate vertically withdrawn from a reservoir of viscous liquid using a combination of diffuse-interface numerical simulation and lubrication analysis. So far available theoretical investigations were commonly conducted by focusing on separate parameter regions, and a complete description of the flow regimes with increasing plate speed is still missing. By solving the full Stokes equations, we present a complete scenario of film transition in the presence of moving contact line. With increasing plate speed, we identify numerically four successive flow regimes in terms of the interfacial morphologies: (1) a stationary meniscus, (2) a speed-independent thick film connected to the liquid bath through a stationary dimple, (3) coexistence of a thick film and the classical Landau–Levich–Derjaguin (LLD) film connected by a propagating capillary shock and (4) a film with a monotonically varying thickness. The characteristics of the film profiles in different regions of the interfaces are analysed with lubrication theory as applicable, and satisfactory agreements with the numerical results are obtained. In particular, we confirm that the onset of film deposition occurs at a vanishing apparent contact angle, consistent with the predictions of lubrication theory. Numerical results suggest that the critical capillary number for the onset of film deposition is smaller than that for the onset of LLD film despite the fact that it is higher than the experimentally observed one, showing that the thick film can be realized in the two-dimensional model. We also demonstrated that the LLD film is triggered by the bifurcation of the stationary dimple, which is found to admit multiple branches of stable and unstable solutions.
In this chapter a wide a range of examples-from the putative simple dip coating process, where a substrate is withdrawn from the coating solution at a constant rate, to the more advanced evaporation induced self-assembly (EISA) process, which leads to well-ordered nanostructured thin-film materials-is covered. In the first part the fundamentals of classical dip coating are presented. Various physical and chemical effects which influence the thickness and microstructure evolution are discussed. The film thickness is set by the competition among viscous force, capillary force, and gravity. Microstructure and properties of the film e.g. depend on the size and structure of the inorganic precursor species, the magnitude of the capillary pressure exerted during drying, and the relative rates of condensation and drying. After the basic aspects modified dip coating techniques which enable the coating of differently shaped substrates such as cylinders, tubes and bottles are briefly presented. Finally different aspects of the EISA process, which is based on the fact that in dip coating film formation occurs through evaporation of solvents concentrating the system in non-volatile species, is shortly reviewed. Thus by means of the silica/surfactant system it is presented how aggregation & gelation can be controlled and functional nanoscopic materials can be generated. It is also briefly shown that EISA can be used to simultaneously organize hydrophilic and hydrophobic precursors into hybrid nanocomposites that are optically or chemically polymerizable, patternable, or adjustable.
Values of the receding contact angle have been obtained between cold trapped sodium and 20% cold worked stainless steel, Type M316, over the temperature range 98 degree to 800 degree C, and on nickel and iron over the range 98 degree to 300 degree C. Though it was found that nickel and iron specimens could be readily wetted by sodium above 250 degree C yielding zero contact angles, austenitic steel specimens generally did not give angles lower than 30 degree . It is postulated that the reason for this is that the oxide on austenitic steel is not reduced by cold trapped sodium.
For practical use of an under-sodium viewer, the behavior of sodium wetting is investigated by modeling the reactive and non-reactive wetting of metallic-plated steels by liquid sodium to simulate sodium wetting. The non-reactive wetting simulation results showed good agreement with Tanner's law, in which the time dependencies of the droplet radius and contact angle are expressed as RN∝t1/10 and θ∝t− 3/10, respectively; therefore, the model was considered suitable for the simulation. To simulate reactive wetting, the model of fluid flow induced by the interfacial reaction was incorporated into the simulation of non-reactive wetting. The reactive wetting simulation results, such as the behavior of the precursor liquid film and central droplet, showed good agreement with sodium wetting experiments using thin Au plating at 250 °C. An important result of the reactive wetting simulation is that the gradient of the reaction energy at the interface appeared on the new interface around the triple line, and that fluid flow was induced. This interfacial reactivity during sodium wetting of thin Au plating was enhanced by the reaction of sodium and nickel oxide through pinholes in the plating.
The problem of determining the thickness of the dragged layer as a function of the speed of the motion of the film and of parameters characteristic of the properties of the fluid is of essential interest for practice. In the chapter, the thickness of the layer and the quantity of fluid carried along when pulling an infinite plate out of a vessel, which is sufficiently large to permit the neglecting of the effect of its walls and of the edges of the plate, is evaluated. The case of low velocity of motion of the plate is considered. In this case, all the surface of the liquid may be separated into two independent regions: (1) the region of the surface situated high above the meniscus and directly dragged by the plate, where the surface of liquid may be taken to be nearly parallel to the plate surface and (2) the region of the meniscus of liquid. The solutions of hydrodynamical equations in both independent regions are presented in the chapter and then both of the solutions that are found are connected.
When a vessel of liquid has been emptied and put aside, a thin film of liquid clings to the inside and gradually drains down to the bottom under the action of gravity. The layer being thin, the motion is very nearly laminar flow, and the curvature of the surface in a horizontal direction may be ignored. Thus the problem for a cylindrical vessel is reducible to that of a wet plate standing vertically.(Received February 01 1930)(Accepted March 10 1930)
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