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1.
Experiments have been performed using sodium, water, white spirit and Freon 113 in a simple small-scale system, to determine the conditions necessary for gas entrainment inception at a vortex with an unstable gas core. The results demonstrate that surface tension effects play a major role and hence they must not be ignored when developing an entrainment-free system.  相似文献   

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In a sodium-cooled fast reactor (SFR), inert gases exist in the primary coolant system either in a state of dissolved gas or free gas bubbles. The sources of the gas bubbles are entrainment and dissolution of the reactor cover gas (argon) at the vessel free surface and emission of the helium gas that is produced as a result of disintegration of B4C control rod material. The gas in the primary system may cause disturbance in reactivity, nucleation site for boiling, etc. Therefore, it is a key issue from the design and safety viewpoint and the allowance level is necessary regarding the gas entrainment at the free surface and the gas bubble concentration in the primary system. In the present study, a gas entrainment allowance level at the free surface is discussed and rationalized for the Japanese SFR (JSFR) design. The influence of the gas entrainment is evaluated using the void fraction at the core inlet. Design criteria for the acceptable level of the gas entrainment and gas concentration are proposed in consideration of the background level of gasses in the coolant. For the purpose, a plant dynamics code VIBUL has been developed to apply to the JSFR design to evaluate the concentration distribution of the dissolved gas and the free gas bubble in the JSFR system. Using the plant dynamics code for the bubble behavior, the background level of the free gas (void fraction at the core inlet) has been obtained. Assuming that the total void fraction should be kept below 105% of the background level, a preliminary design allowance level of gas entrainment is proposed as the map in terms of the entrainment rate and the entrained bubble radius. Furthermore, the possibility of bubble removal and design requirement of the device is investigated to satisfy the allowance level. It is noted that the background level is already very low in comparison with the induced void reactivity by the void passing the reactor core.  相似文献   

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It is necessary to understand effects of scale and fluid properties on gas entrainment phenomena for prediction of gas entrainment in a fast breeder reactor (FBR). In the present study, three models of different scales but of similar geometry were used for water tests to examine the effects of scale and viscosity. The results have shown that the critical Froude (Fr) number, above which gas entrainment appears, drastically decreases as the scale increases. A prediction method using the Fr-Re map is proposed in the present paper for the sodium flow in an FBR.  相似文献   

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An experimental and analytical investigation of onset condition of gas pull through and liquid entrainment in a single inclined branch to the arbitrary direction was performed in the present study. Since previous studies have been made only for specific angles of 0° and ±90°, it is hard to apply them to the case of branch off to the arbitrary direction. In the present study, series of experimental works was made with a horizontal header of 184 mm inner diameter with a single branch pipe which can be attached in nine different orientations of 0°, ±30°, ±45°, ±60°, ±90° angles and with two different diameters of 16.0 and 24.8 mm, respectively. Also, a simple mechanistic model is developed here based on the force balance at the top of the vortex on the surface of the stratified water. The onset condition due to the vortex breakup for the branch oriented with angle of θ was determined as and the onset condition due to the ascending film was which is similar to that of side branch. It was found that the present model predicted experimental data well in terms of the direction and diameter of the branch pipe. The present model and data may be useful in determination of the quality of flow through the inclined branch which is one of key parameter in the safety study of hypothetic small break loss of coolant accident in the nuclear power plant.  相似文献   

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Liquid entrainment and off-take through the break at the top of a vessel   总被引:1,自引:0,他引:1  
In order to determine the bleed capacity of the safety depressurization system (SDS) of Advanced Power Reactor 1400 (APR1400) in the case of total loss of feed water (TLOFW), we performed an experimental study of liquid entrainment and liquid off-take from the swelled two-phase mixture surface in a vessel. A total of 220 experimental data on the entrainment and off-take are obtained using a test vessel with a height of 2.0 m and an inner diameter of 0.3 m and a top break with a diameter of 0.05 m. Two-phase mixture levels are measured by an ultrasonic sensor within ±1.77% with respect to the visual level data. Droplet entrainment data are obtained with and without the top break and are compared with the existing pool entrainment data. The present droplet entrainment data have higher values than the existing pool entrainment data due to (a) the pulling toward the break of the liquid deentrained on the top wall of the vessel and (b) gas acceleration in the vicinity of the break. In the present experiment, droplet entrainment, Efg, strongly depends upon and is proportional to the seventh power of in the same way as the off-take data. The empirical correlation for the onset of off-take is developed in terms of the Froude number (Frg) at the break and the non-dimensional inception height (hb/d). This correlation shows agreement with the present experimental data within ±15%. The present off-take quality data show agreement with Schrock's off-take quality correlation with the rms error of 15.8%.  相似文献   

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The degradation of phenol by pulsed discharge plasma above a liquid surface(APDP) and under a liquid surface(UPDP) was compared. The effects of discharge voltage, discharge distance,initial solution conductivity and initial p H on the removal of phenol were studied. It was concluded that the removal of phenol increases with increasing discharge voltage and with decreasing discharge distance in both APDP and UPDP systems. An increase in the initial solution’s conductivity has a positive effect in...  相似文献   

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A two-dimensional transient heat conduction model for rewetting a hot surface by a falling liquid film predicts that for stainless steel, Inconel or Zircaloy only a wall thickness of some 0.020 in. takes part in the rewetting process in steam at 100–1000 psia. The rewetting rate is nearly independent of heat flux and thermal conductivity, but increases with pressure and decreases with volumetric heat capacity.  相似文献   

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Translated from Atomnaya Énergiya, Vol. 66, No. 5, pp. 328–331, May, 1989.  相似文献   

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A surface-ionization ion source for the use of a thick target has been studied by an isotope separator on-line at INS using the 40Ca(p,2pn)38K reaction. The ionization efficiency and release time were measured for CaC2, CaO and CaF2 targets. The measured efficiency turned out to be about 20% both for tantalum and platinum surface ionizers. The release time was also deduced for each target at various values of temperature by measuring time distributions of the extracted radioactivity after bombarding the target for a short time.  相似文献   

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The plasma-neutral gas structure generated in a magnesium cathodic arc operated with oxygen gas at a constant current of 50 A has been investigated by employing a simplified one-dimensional fluid model.The model includes elastic collisions and charge-exchange reactions between metallic particles and gas molecules,and also generation and recombination of gaseous ions by electron impact.The distribution profiles of density and velocity of species along the axial direction were obtained at diferent background gas pressures(in the range of 0.7~3.0 Pa)by this model.A comparison with the experiments was made.At lower gas pressures,the depositing particles were mainly the metallic ions with a larger kinetic energy.As the gas pressure increased,the magnesium atoms with smaller kinetic energy acted as the dominant depositing species.Determined by the minimization of the system’s total energy,MgO(100)or/and MgO(110)orientation appeared easily in the MgO films at lower gas pressures,and at higher gas pressures,the film preferred orientation was MgO(111).  相似文献   

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