Sodium Mist Research Articles

Numerical simulation of sodium mist behavior in turbulent Rayleigh-Bénard convection using new developed mist models

In order to evaluate the mist behavior in the cover gas region of Sodium-cooled Fast Reactors (SFRs) in good accuracy, turbulent model for Rayleigh-Bénard convection (RBC) was selected, and the Reynolds-averaged number density and momentum equations for mist behavior were developed and incorporated into the OpenFOAM code. In the first stage, the RBC in a simple parallel channel was calculated using Favre-averaged k-ω SST model. The average temperature and flow characteristics agreed well with results from DNS, LES, and experiments. Then the basic heat transfer experiment simulating the cover gas region of SFRs was calculated using this turbulent model and new mist models. The calculated average temperature distribution in the height direction and the mist mass concentration agreed well with the experimental results. We developed a method that could simulate the mist behavior in turbulent RBC environments and the cover gas region of SFRs with high accuracy.

Flame structures and ignition thresholds of hydrogen jets containing sodium mist under various gas concentrations

ABSTRACT Non-premixed combustion of hydrogen jets containing sodium vapor and mist reduces threats to reactor containment integrity in sodium-cooled fast reactors (SFRs) because it gradually consumes hydrogen gas generated mainly by a reaction between sodium and concrete. Previous studies have been limited to experimentally determining ignition thresholds on the jet temperature and the sodium concentration under specific gas concentrations. In this study, ignition experiments on hydrogen jets containing sodium mist were carried out at a specific jet temperature and sodium concentration under various gas concentration conditions (1–15 vol% hydrogen and 3–21 vol% oxygen). As a result, a stable sodium flame was observed in the jet and then formed a lifted hydrogen flame from a fuel nozzle outlet. An attached hydrogen flame on the outlet was also formed under high hydrogen concentration conditions. These flame structures seemed to be attributed to hydrogen flame propagation, which depends on the hydrogen concentration, jet temperature, and jet velocity. Additionally, the experimental results revealed ignition thresholds on the gas concentration and indicated a flammable region where the hydrogen-sodium jet combustion was more advantageous than an explosive premixed hydrogen combustion. Our study will enable the advancement of safety assessment technology in SRFs.

Visualizing an ignition process of hydrogen jets containing sodium mist by high-speed imaging

ABSTRACT In severe accident scenarios for sodium-cooled fast reactors, it is desirable to gradually consume hydrogen generated by various ex-vessel phenomena without posting a challenge to containment integrity. An effective means is combustion of hydrogen jets containing sodium vapor and mist, but previous studies have been limited to determining ignition thresholds experimentally. The aim of this study was to visualize the ignition process in detail to investigate the ignition mechanism of hydrogen–sodium mixed jets. The ignition experiments of the hydrogen jet containing sodium mist were carried out under a condition of little turbulence. The ignition process was measured with an optical measurement system comprised of a high-speed camera and an image intensifier, and a spatial distribution of luminance was analyzed by image processing. Detail observation revealed that sodium mist particles burned as scattering sparks inside the jet and that hydrogen ignited around the mist particles. Additionally, the experimental results and a simple heat balance calculation indicated that the combustion heat of sodium mist particles could ignite the hydrogen as the heterogeneous ignition source in the fuel temperature range where the mist particle formation was promoted.

Radiative Heat Transfer in a Gas Space Filled with Sodium Mist. In Case of Polydispersed Sodium Mist Particles.

Radiative heat transfer through a cover gas between upper wall and lower liquid sodium surface, filled with polydispersed sodium mist particles, is investigated numerically by Monte Carlo Method. Radiative properties of sodium mist such as extinction coefficient and scattering phase function are calculated using particle distributions for sodium mist by Mie theory. Using these properties the radiative heat flux is computed for the cover gas space of gray isotropic and nongray anisotropic scattering particles, respectively. The results obtained show that, the heat flux decreases with increasing concentration of sodium mist, however, the effect of sodium mist on total heat flux is relatively low.

Radiative Heat Transfer in a Gas Space Filled with Sodium Mist. In Case of Monodispersed Sodium Mist Particles.

Radiative heat transfer through a gas space between horizontal parallel walls, filled with monodispersed sodium mist particles, is investigated numerically by Monte Carlo method. Firstly, radiative properties such as scattering phase function, Albedo, scattering, absorption and extinction coeffcients are calculated using Mie theory. From these propertis obtained the radiative heat flux is computed numerically for varying particle diameter d=l∼10μm, sodium mist concentration Cm=0.05∼50.0 g/m3 and distance between walls H=0.1∼1.5m. In calculation, sodium mist particles are treated as nongray anisotropically scattering medium. The results indicate that heat flux has the smallest values at the diameter of about 2.0 μm.

Analytical Study on Mass Concentration and Particle Size Distribution of Sodium Mist in Cover Gas Phase of LMFBR Reactor Vessel

Click to increase image sizeClick to decrease image sizeKEYWORDS: FBR type reactorsreactor vesselscover gassodiummistmass concentrationparticle size distributionhigh temperaturetemperature dependence

Analytical Study on Mass Concentration and Particle Size Distribution of Sodium Mist in Cover Gas Phase of LMFBR Reactor Vessel.

To improve the performance of the roof slab for LMFBRs, information on the mass concentration and particle size distribution in the gas space enclosed by the reactor vessel is important, however experimental data are very limited(1)(2). Himeno(1) measured the mass concentration and particle size in the gas phase using small sodium pots. Schi_itz et al.(2) also tried to determine the mass concentration and the particle size distribution at high temperatures. However, mist behavior in the cover gas is very complicated and those values in the actual FBR cover gas have not been completely clarified. A few efforts have been devoted to solving the equations that govern particle size distribution of the mist. Himeno(1) and Kudo(3) obtained a solution by representing the mist size with its geometric diameter. However, in this method, the governing equations become very complicated and a large numerical error may be induced because the addition/subtraction law does not hold for the change in the geometric diameter due to each coagulation.

Analytical study on mass concentration and particle size distribution of sodium mist in cover gas phase of lmfbr reactor vessel

To improve the performance of the roof slab for LMFBRs, information on the mass concentration and particle size distribution in the gas space enclosed by reactor vessel are important. This paper deals with development of an analytical model to predict precisely the mist concentraion and its particle size distribution.

Radiative Properties of Sodium Mist

Radiative Properties of Sodium Mist

Radiative properties of sodium mist.

Spectral variations of the extinction coefficient, the albedo and the asymmetry factor of sodium mist—required for calculations on the radiative heat transfer taking place in the cover gas space of an LMFBR—have been obtained analytically on the basis of Mie's theory. It is found that in the near-infrared region, the extinction coefficient remains almost independent of wavelength, at a level that rises with lowering temperature of the mist; in the same region, the albedo similarly shows little dependence, not only on wavelength but also on temperature. Moreover, with increasing wavelength, the scattering pattern is found to change from forward to backward.

Development of a Sodium Vapor Pressure Meter Using Beta-Alumina Ceramics

A program was carried out to develop a sodium vapor pressure measuring system using beta-alumina ceramics for use in developing sodium vapor traps and monitoring sodium mist in cover gas for fast breeder reactors (FBRs) and test facilities. The sensor device was tested in a vacuum glass capsule. Its output agreed well with theoretical results. Moreover, it proved to have the capability of measuring a lower vapor pressure near 10−5 Torr without any calibrations.The measuring system, consisting of a beta-alumina sensor device, gas circulating pump, gas heater, and mist trap, is applicable to FBR plants and test facilities that contain much sodium mist and to a transient monitoring system. This system was tested in an isothermal sodium vapor circulation test loop under conditions involving much sodium mist.

Effect of Barriers on Sodium Mist Deposition on LMFBR Components

Tests were made to evaluate the effect of two barriers (a convection barrier and a drip receiver) against sodium mist deposition on LMFBR conponents in the cover gas space. Two models of LMFBR rotating shield plugs (1,800 mm in height, 680 and 850 mm in diameter) and a sodium test tank were manufactured for this purpose, and the mist deposition rate on the walls of these models was measured both in the cases with and without a barrier. The sodium pool temperature during the test was 580°C. In parallel with these tests, the relation between the form of deposit and the wall temperature was examined to determine the critical wall temperature above which deposits do not accumulate. This was conducted by exposing a vertical stainless steel cylinder to cover gas entrained with mist over 500°C sodium for 30 to 1,000 h. The test results revealed that the barriers functioned effectively, and they reduced the local deposition rate near top of the annulus by three orders of magnitude relative to the cases without a barrier. The critical wall temperature to avoid deposit accumulation was found to be 100 to 150°C.

Effect of barriers on sodium mist deposition on LMFBR components.

Tests were made to evaluate the effect of two barriers (a convection barrier and a drip receiver) against sodium mist deposition on LMFBR conponents in the cover gas space. Two models of LMFBR rotating shield plugs (1,800 mm in height, 680 and 850 mm in diameter) and a sodium test tank were manufactured for this purpose, and the mist deposition rate on the walls of these models was measured both in the cases with and without a barrier. The sodium pool temperature during the test was 580°C. In parallel with these tests, the relation between the form of deposit and the wall temperature was examined to determine the critical wall temperature above which deposits do not accumulate. This was conducted by exposing a vertical stainless steel cylinder to cover gas entrained with mist over 500°C sodium for 30 to 1,000 h. The test results revealed that the barriers functioned effectively, and they reduced the local deposition rate near top of the annulus by three orders of magnitude relative to the cases without a ...

Investigation of Sodium Mist Trapping Efficiency in Mesh-Packed Trap

An analysis is made on the trapping efficiency of a sodium mist trap brought by change in the mist particle size distribution. The trapping efficiency is represented in terms of the rate of mist adhesion onto the mesh wires. A log-normal distribution function is assumed for the particle size distribution in the mist at trap inlet. The analytical results yield the following conclusions: 1. The trapping efficiency is greatly influenced by [dbar]p , the mean particle diameter of the mist, and reduces to a minimum in the region of [dbar]p =1–10 μnm, for a trap packed with mesh of diameter currently practiced (−0.1 mm). Compared with [dbar]p , change in the standard deviation of particle size distribution exerts a much smaller influence on the trapping efficiency.2. The efficiency also depends on the flow rate of the mist through trap, represented by the Reynolds number Re expressed in reference to the wire diameter. With the trap configuration and other factors adopted in the analysis, lowering Re to 0.01, improves almost to unity the trapping efficiency, which is governed in this condition principally by the rate of mist diffusion.3. The calculated trapping efficiency agrees well with the corresponding values determined from the measured sodium concentrations in the inlet and the outlet gases.

Investigation of sodium mist trapping efficiency in mesh-packed trap.

An analysis is made on the trapping efficiency of a sodium mist trap brought by change in the mist particle size distribution. The trapping efficiency is represented in terms of the rate of mist adhesion onto the mesh wires. A log-normal distribution function is assumed for the particle size distribution in the mist at trap inlet. The analytical results yield the following conclusions: 1. The trapping efficiency is greatly influenced by [dbar]p , the mean particle diameter of the mist, and reduces to a minimum in the region of [dbar]p =1–10 μnm, for a trap packed with mesh of diameter currently practiced (−0.1 mm). Compared with [dbar]p , change in the standard deviation of particle size distribution exerts a much smaller influence on the trapping efficiency. 2. The efficiency also depends on the flow rate of the mist through trap, represented by the Reynolds number Re expressed in reference to the wire diameter. With the trap configuration and other factors adopted in the analysis, lowering Re to 0.01, i...

Sodium Mist Behavior in Cover Gas Space of LMFBR Out-Pile Experiment

Sodium mist behavior in argon cover gas space over sodium pool was investigated experimentally using of a test vessel having cover gas volume of ∼100l. Mass concentration and gravitational settling flux of the mist (i.e. sodium aerosol) were determined between pool temperature range of 290∼520°C. Apparatuses used for the concentration determination were a He-Ne laser mist concentration meter (LCM) and mist traps, which were developed specifically for the present experiment. The mist gravitational settling flux φ was determined by using of collection plates, which were exposed to the mist entrained cover gas over sodium pool. The experimental results revealed that the concentration C was very high from 0.15 to 20g/m3. It increased with pool temperature. The mist particle radii, which were determined from the gravitational settling flux φ and decay curve of the concentration, were from 1.5 to 13 μm in the range of the present experiment. The vapor evaporation rate φe from the pool surface, which were also determined from the experimental φ data, were found to increase with saturated vapor pressure Ps at pool surface. This rate did not depend so strongly on experimental geometries and cover gas flow convection pattern over sodium pool. Evaluations of transient C changing and steady state C fluctuation indicated that the mist formation was occurred near the pool surface.

Sodium mist behavior in cover gas space of LMFBR. Out-pile experiment.

Sodium mist behavior in argon cover gas space over sodium pool was investigated ex-perimentally using of a test vessel having cover gas volume of 100l. Mass concentration and gravitational settling flux of the mist (i.e. sodium aerosol) were determined between pool temperature range of 290520°C. Apparatuses used for the concentration determination were a He-Ne laser mist concentration meter (LCM) and mist traps, which were developed specifically for the present experiment. The mist gravitational settling flux φ was determined by using of collection plates, which were exposed to the mist entrained cover gas over sodium pool.The experimental results revealed that the concentration C was very high from 0.15 to 20 g/m3. It increased with pool temperature. The mist particle radii, which were determined from the gravitational settling flux ψ and decay curve of the concentration, were from 1.5 to 13 μm in the range of the present experiment. The vapor evaporation rate φe from the pool surface, which were also determined from the experimental ψ data, were found to increase with saturated vapor pressure Ps at pool surface. This rate did not depend so strongly on experimental geometries and cover gas flow convection pattern over sodium pool. Evaluations of transient C changing and steady state C fluctuation indicated that the mist formation was occurred near the pool surface.

Using Anemometer for Particle Size Measurement of Sodium Mist

Using Anemometer for Particle Size Measurement of Sodium Mist

Sodium vapor deposition on simulated model of LMFBR rotating shield plug annulus. II. Local deposition rates and gas flow patterns within annulus.

The paper presents sodium vapor deposition on LMFBR rotating shield plug simulated annulus both experimentally and numerically. Experiment carried out was measurements of the deposition rate and temperatures to investigate role of cover gas natural convection within the annulus. Numerical study was aimed to investigate effect of the vapor condensation to the overall or the apparent deposition rate in semi-quantitatively. The numerical results revealed that the deposition is mainly caused by sodium mist deposition, but not by the vapor condensation. Regarding the role of cover gas natural convection, clear correlation was found between the generalized deposition rate and Rayleigh number of the annulus. This correlation indicated that the mist was transfered to the walls by gas natural convection flows. Gas flow patterns estimated from the deposits distributions on the annular wall and temperatures were circumferential. Probably due to these flows, the dense mist was transfered up to top of the annulus, whe...

Using anemometer for particle size measurement of sodium mist.

Using anemometer for particle size measurement of sodium mist.