[en] The breakup of two-dimensional liquid drops is numerically investigated at around the critical Weber number. The Moving Particle Semi-implicit (MPS) method is used to solve the unsteady Navier-Stokes equations for both the drops and the ambient fluid. The two dominant forces affecting drop breakup, pressure drag and surface tension force, are verified using the two benchmarks: pressure distribution on the surface of a cylinder in a uniform flow and oscillation of a square drop under surface tension force. The results show that the breakup process occurs in two stages. During the first stage, the drops become stretched and thinned normal to the flow direction of the ambient fluid. During the second stage, detached points appear on the surface of the drops, which are ascribed to the unstable growth of surface waves. The post-breakup topology of the drops is dependent on the value of the Weber number: the larger the Weber number is, the more detached points on the surface of the drops emerge. Another feature commonly shared in the two stages is that some fine fragmentations are stripped from the equatorial edges of the drops. The critical Weber number is predicted to be 13 for uranium dioxide drops in water, at which breakup regime is consistent with the so-called vibration regime

[en] Flashing jets are numerically simulated at two dimensions for different superheat degree. Evaporation mode for flashing jets is identified as surface boiling mode based on the experiments and theoretical analyses. The homogeneous non-equilibrium relaxation model is used to model the phase change. The dynamic governing equations are solved by the Moving Particle Semi-implicit method (MPS). The simulation results show that a flashing jet emerging from a nozzle is torn away into a conic-shaped liquid core under surface boiling and extinguishes for some distance downstream of the nozzle exit. The extinction length of flashing jets decreases with increase of superheat degree for a given injection pressure. Moreover, approximate homogeneous two-phase flow is engendered from the jet interface and thus a cloud of spray is formed to surround the central liquid core of flashing jets. The above numerical simulation results are well consistent with the relevant experimental observations. (authors)

[en] The study of the thermodynamic equilibrium of the liquid sodium-hydrogen system is carried out on the basis of chemical engineering thermodynamics. The relationship between the hydrogen partial pressure above the surface of liquid sodium and hydrogen concentration in liquid sodium is presented. The quantitative dependence of the Sieverts constant on the temperature is obtained from above. And the experimental data of the Sieverts constant from some references are analyzed. Moreover, the temperature dependence of hydrogen solubility in sodium is given, and the comparison with the experimental data is made

[en] A mathematical model is presented for hydrogen diffusion in a fast reactor shell-tube steam generator (SG) with a small water/steam leak to judge small water/steam leaks in SG with a hydrogen meter. The model simulates sodium flow in the steam generator as quasi-continuum. The model uses volume porosity, area permeability and distributed resistance to model the tubes and support plates. Meantime. The model of hydrogen and hydroxide ions diffusion is also established with the dissociation of hydrogen gas and NaOH in excess sodium. Water injection experiments in a sodium loop showed that the hydrogen meter response to the predicted hydrogen concentration agreed well with the experiment data

[en] In order to study the effect of thermodynamic parameters of steam generator in fast reactor on the leak response of a small leak detection system, the author sets up the model of sodium-water products transport and diffusion in the steam generator. For the first time, a hydrogen line density concept is proposed, and the controlling differential equation of the hydrogen line density and hydroxide ion are established. In the end, the tri-dimensional transport and diffusion equation is established. By comparison between the computed results and measurement of the hydrogen detector response on H^- concentration in the sodium exit of steam generator, it shows that the model can exactly predict the transport and diffusion process of sodium-water reaction products on small water/steam leak in steam generator of fast reactor

[en] In order to calculate the sodium-water reaction products transport and diffusion in occurrence of small water leak in steam generator, a three dimensional numerical model of sodium steady flow in steam generator of fast reactors is established. The numerical model uses the distributed resistance along with volumetric porosity and surface permeability to model the effect of tubes on sodium flow in the steam generator. The distributed resistance of banks of tubes is correlated by the pressure drop formula of the flow perpendicular to tubes and the flow parallel to the tubes. Turbulence effects are modeled using a κ-ε model. Shell and support plate walls are modeled using the wall function approach. Good agreement is obtained between the computed results and experiments

[en] Falling liquid film is widely used in nuclear engineering, thermal engineering, chemical engineering, and electronics owing to its high efficiency of heat and mass transfer with small temperature difference, flow rate and power consumption, such as cooling towers, AP1000 passive containment cooling system (PCCS), and multiple-effect distillation (MED) for seawater desalination. To investigate the fluid dynamics of the falling liquid film, a simultaneous measurement technique with only one camera, which combined planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV), has been applied in the liquid film flow experiment. Image acquisition in this research utilizes a long distance microscope and provides high spatial resolution at a relative large working distance. With this experimental method, it becomes feasible to generate streamwise velocity evolution of film flow on an inclined plane. In addition, film thickness measurements are performed using a laser confocal displacement technique enabling investigation of the wave dynamics. Isothermal film flow with systematic variations of both Reynolds number (Re=11.5∼32.9) and the inclined angel (β=20deg) are investigated. Comparison between experimental results and previous published results is made to verify the measurement method. (author)

[en] The paper presents a three-dimensional model of sodium-water reaction product transport in steam generators with a small water/steam leak. The model is used to study the effects of thermodynamic parameters of steam generators of Liquid Metal Fast Breeder Reactor (LMFBR) on the leak response of a small water leak detection system and to optimize the leak detection system design. A hydrogen gas line density concept is used to develop the differential equation of hydrogen ion transport. The model can be applied to analyze the leak response of hydrogen meters, oxygen meters and other concentration-type leak detection systems. The model was verified with water injections into sodium with different temperatures in a simple sodium loop with a hydrogen meter. (author)

[en] In this study, we carried out the numerical simulation of gas flow across a helically coiled tube bundle, which is fitted in the annular space between a central spine and an outer casing. We focused on the effect of clearances at the inner and outer radial boundaries on the gas flow distribution and thermal mixing in the tube bundle. The conservation equations of mass, momentum and energy were numerically solved by computational fluid dynamics. It was demonstrated from the numerical simulation results that (1) the gas flow distribution in the tube bundle is very sensitive to clearances at the inner and outer radial boundaries, and even a very small variation of clearances would lead to a considerable change in the average velocity profile, which correspondingly leads to a great deviation of the gas flow distribution away from the original one; (2) the clearance effect on thermal mixing is not as strong as that on gas flow distribution; (3) the Reynolds number has little effect on the gas flow distribution and thermal mixing, the latter of which is in agreement with the results of Achenbach experiments. (author)

[en] The one dimension mathematics model is established for the diffusion of sodium-water reaction products in steam generator (SG) and leak detection system (LDS) for liquid metal-cooled fast breeder reactor. The effects of sodium temperature and flowrate of SG and LDS are analyzed and the useful results are obtained from numerical calculations and experiments in a sodium loop. The results show that increasing the sodium flowrate of SG and LDS, the response time of LDS is decreased, but the sensitivity is lowered. The effect of sodium temperature of SG on the response time of LDS is less than that of sodium flowrate in SD, however, it can make the sensitivity of LDS higher when the sodium temperature is raised