Results 1 - 10 of 1420
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[en] Highlights: •New entrainment models developed on the basis of our early research are compared with previous models. •New models are written into RELAP5 code. •A typical 2-in SBLOCA transient in AP1000 is simulated and discussed by modified RELAP5. -- Abstract: Application research of two new liquid entrainment models for separately predicting the beginning of entrainment and branch entrainment quality is performed which is a continuation of previous experimental and theoretical studies on the entrainment at T-junction. The new onset entrainment model and branch quality model are developed on the basis of the scaling experiment for studying ADS-4 entrainment phenomenon in AP1000 plant, and the two new models along with previously published entrainment models are compared. The results show that previous models in the background of entrainment through a small break of primary pipe are not suitable for predicting the entrainment through a large size branch (e.g. ADS-4 pipe), while the two new models have a larger applicability. Also, the new entrainment models are written into the RELAP5 code, and then a typical 2-in SBLOCA transient in AP1000 is simulated separately by the modified RELAP5 and the original RELAP5 to further discuss the applicability of new models for the simulation of entrainment through ADS-4. The results show that the modified RELAP5 can get more reasonable simulation results. In view of original RELAP5 overestimated core coolant inventory, the modified RELAP5 can get a conservative core coolant inventory. Hence we can conclude that the new entrainment models are more suitable for the simulation of entrainment through ADS-4.
[en] In the present invention there is provided an accelerator for charged particles, comprising: a vessel adapted to enclose a stream of charged particles along a preselected track; and drive means juxtaposed with said vessel for generating therein a magnetic field travelling in a preselected direction relative to each point of the track with the magnetic flux vector of the field transverse to the track at all points. This sets the particles in motion along the track with a velocity having a predetermined relation to the velocity of the travelling field. (auth)
[en] A bifurcation of transition that destroys generalized chaos synchronization is considered. This transition frequently occurs in regimes of subharmonic chaos entrainment where synchronization can be abruptly terminated due only to an almost unnoticeable change in the shape of the driving attractor. We explore the main cause of this sensitivity and ascertain the mechanism behind this transition
[en] Prismatic sectional files, staggered one behind the other, enclose the tubes of the feedwater piping system. These sectional files of the steam moisture separator are dimensioned in such a way that the gaps between the individual rods of the files become tighter in the direction from the flowing - in steam towards the feedwater heater. With their lower end the sectional files are arranged on a plate with rim and water drain. By these measures there will be achived that the stagnation of the heating steam does not immediately affect the piping system. (DG)
[de]Prismatische Profilreihen umschliessen hintereinander versetzt angeordnet die Rohre des Speisewasserrohrsystems. Diese Profilreihen des Dampfnaesseabscheiders sind so bemessen, dass die Spalte zwischen den einzelnen Stangen der Reihen in Richtung vom einstroemenden Dampf zum Speisewasservorwaermer hin enger werden. Die Profilreihen sind mit ihrem unteren Ende auf einer Platte mit Bordrand und Wasserablauf angeordnet. Durch diese Massnahmen wird erreicht, dass der Stau des Heizdampfes nicht unmittelbar auf das Rohrsystem einwirkt. (DG)
[en] When increasing the degree of fluidity of previously aerated cementitious mixtures, there is a problem of maintaining their correct aeration. Most of the available superplasticizers cause a significant increase of the air content of concrete mixtures. The problem of compatibility of superplasticizer and air-entraining admixture increases in case of multicomponent Portland cement, due to different effects of these additives. It comes down to achieving a compatibility of the three variables mentioned in the title of the paper, due to the required air entrainment and consistency of mixture. Achieving compatibility of such a system requires a series of experimental studies that were presented in the paper together with their resulting indications. In case of previously air-entrained concrete that is made with an air-entraining cement, after the addition of new generation SP occurs very large increase in air entrainment. The air-content of mixture according to EN 480-1 may be higher than 13%. (paper)
[en] Momentum flux is a very important parameter for predicting the mixing potential of injection processes. Important factors such as spray penetration, spray cone angle, and air entrainment depend largely on spray momentum. In this article, a model is obtained which is able to predict the spray tip penetration using as an input the spray momentum flux signal. The model is based on the division of the momentum flux signal into momentum packets (fuel parcels) sequentially injected, and the tracking of them along the spray. These packets follow a theoretical equation which relates the penetration with the ambient density, momentum, spray cone angle and time. In order to validate the method, measures of momentum flux (impingement force) and macroscopic spray visualization in high density conditions have been performed on several mono-orifice nozzles. High agreement has been obtained between spray penetration prediction from momentum flux measurements and real spray penetration from macroscopic visualization
[en] The purpose of this research was to investigate the de-entrainment of boron for evaporators used in nuclear power plants. The forced circulation and semi-continuous type evaporator was used in the experiment. Cyclone and glass-wool packed column which is supposed to provide good decontamination factor as well as easy maintenance, were selected as de-entrainment device to be used in the evaporation of radioactive liquid wastes. The de-entrainment device combined with cyclone and glass-wool column has shown overall DF more than 1000 for boron. (Author)
[en] The cooling water composition and microbial components of biofilms attached to stainless steel wafers submerged in three lake water types were evaluated to determine whether their biofouling potential differed in a predictable manner. The composition of the lake waters was different which affected biofilm composition, where the predominance of specific microbial groups varied between test systems and with time. Some prediction of biofouling potential was possible, and it was concluded that the cooling water in the vicinity of Bruce NGS had the lowest biofouling potential whereas greater biofouling could be expected in the Pickering and Nanticoke stations
[en] Stratified interfaces are present in many geophysical flow situations, and transport across such an interface is an essential factor for correctly evaluating the physical processes taking place at many spatial and temporal scales in such flows. In order to accurately evaluate vertical and lateral transport occurring when a turbulent flow impinges on a stratified interface, the turbulent entrainment and vorticity generation mechanisms near the interface must be understood and quantified. Laboratory experiments were performed for three flow configurations: a vertical thermal, a sloping gravity current and a vertical turbulent jet with various tilt angles and precession speeds. All three flows impinged on an interface separating a two-layer stably stratified environment. The entrainment rate is quantified for each flow using laser-induced fluorescence and compared to predictions of Cotel and Breidenthal (1997 Appl. Sci. Res. 57 349-66). The possible applications of transport across stratified interfaces include the contribution of hydrothermal plumes to the global ocean energy budget, turbidity currents on the ocean floor, the design of lake de-stratification systems, modeling gas leaks from storage reservoirs, weather forecasting and global climate change.
[en] Pure thermal plumes have been experimentally investigated under swirling conditions. Such conditions are applied upon the heated source impinging directly on the plume development. Results clearly underlined the existence of a threshold swirling number. Below the latter, i.e., at small swirling velocities, ascendant flow behaves like a classical static plume while at a high swirling number, the flow is clearly affected even if characteristic power laws are still valid. However, swirling of the source favors transition from laminar to turbulence as well as breakdown of coherent structures all around the plume motion. A direct measurement method was applied in order to assess instantaneous entrainment coefficients, and results clearly show appreciable influence of the swirling motion on the plume development. The driving mechanisms, i.e., contraction and expulsion phenomena, are strongly amplified and as a consequence directly interact on entrainment