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1.
In the direct vessel injection (DVI) system downcomer, the direct emergency core coolant (ECC) bypass is activated during the reflood phase of a large-break loss-of-coolant accident (LBLOCA) by the interaction between the downward-flowing liquid-film and the transverse gas flow. Direct ECC bypass is reportedly the major bypass mechanism of ECC, and various experiments have been performed to obtain detailed information about the ECC bypass in a DVI downcomer. These lead to a proposed new scaling methodology, named ‘modified linear scaling’, which is expected to preserve the phase distribution in the downcomer and the ECC bypass phenomena. In the present study, modified linear scaling was experimentally validated in air–water tests comprising Test 21-D of the upper plenum test facility (UPTF). The counterpart tests of UPTF Test 21-D were performed in 1/7.3 and 1/4.0 scale models of a UPTF downcomer, and the test results were compared with the experimental data of UPTF Test 21-D. Two important parameters of direct ECC bypass – the normalized liquid-spreading width on the downcomer wall and the direct ECC bypass fraction, which is the fraction of input water bypassed out the broken cold-leg – were considered in the validation. The comparison revealed that the scaling parameters of direct ECC bypass are well preserved in the prototype and reduced models, from which we conclude that the modified linear scaling methodology is appropriate for designing a reduced test facility and for a scaling analysis of direct ECC bypass in the reflood phase of an LBLOCA. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(10):1319-1326
Results from two integral effect tests were compared to discuss the effect of break location between the direct vessel injection (DVI) nozzle and cold leg during the small-break loss of coolant accident (SBLOCA) scenario. One is the SB-DVI-09 test for a 6-inch (50% break area of a DVI nozzle) DVI line break and the other is the SB-CL-06 test for an equivalent break size of cold leg. Both counterpart tests were performed with the same control logic and initial/boundary conditions except for different break locations of the DVI line and cold leg. Experimental results showed that the maximum heater surface temperature increased more with the broken DVI nozzle (SB-DVI-09) than with the broken cold leg (SB-CL-06) due to the delayed and simultaneous occurrence of the loop seal clearing and the momentary decrease in the collapsed water level in the core region. 相似文献
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A series of tests were performed to evaluate inventory depletion as a reactor vessel undergoes depressurization in the absence of any emergency core coolant system injection (ECCS). These tests were carried out in a scaled representation of a reactor vessel which was initially filled with saturated water up to the elevation of the hot legs. Depressurization valves installed on take-off lines from the hot legs were opened and level swell ensued in the reactor vessel initiating a two-phase blowdown. This was followed by subsequent single-phase discharge transient which in some cases led to core uncovery. A combined model encompassing the two-phase and single-phase discharge portions of the transient is proposed. The inventory-versus-pressure traces obtained from the model compare well with the experimental results. These traces are discussed as bounding trajectories for a large class of small break loss of coolant accident (LOCA) transients which otherwise must be considered individually. 相似文献
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An analytical model that includes the steam condensation effect has been derived and a parametric study has been performed. In addition, a series of experiments were performed and a total of 34 experimental data for the onset of countercurrent flow limiting (CCFL) in nearly horizontal countercurrent two-phase flow have been obtained for various flow rates of water. Comparisons of the present CCFL data with slug formation models show that the agreement between the present as well as the existing model and the data is about the same. However, the deviation between Taitel and Dukler’s model predictions and the data is the largest when jf<0.04 m s−1. A parametric study of the effect of condensation using the present model shows that, when all local conditions are similar, the model predicted local gas velocities that cause the onset of flooding are slightly lower when condensation occurred. Based on the visual observation and the evaluation of the present work, it has been concluded that the criterion derived for the onset of slug flow can be directly used to predict the onset of inner flooding in nearly horizontal two-phase flow within the experimental ranges of the present work. 相似文献
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单粒子翻转可能造成星载电子系统的损伤,甚至使之失效.本文针对解决皮卫星数据存储的可靠性问题,提出一种新的纠错编码:交叉正反码,并将之与常用的三倍冗余判决(TMR)技术进行了比较研究. 相似文献
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An experimental study was conducted to investigate the effect of non-condensable gas and wavy water film on condensation heat transfer. The experiment was performed in a nearly horizontal (4.1°) square duct of 0.1 m height, 0.15 m width and 1.52 m length at atmospheric pressure. A water film in a steady thermal condition was injected to simulate the effect of a wavy interface on the condensation. The experimental data for the heat transfer coefficient and the interfacial structure of the wavy condensate were obtained along with the three parameters: air mass fraction, mixture velocity and film flow rate. When the interface is smooth, the heat transfer coefficients with or without non-condensable gas agree reasonably with the previous theories. The waviness of condensate film increases the heat transfer up to several tenths of a per cent. 相似文献
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Multidimensional thermal hydraulics in the APR1400 (Advanced Power Reactor 1400 MWe) downcomer during a large-break loss-of-coolant accident (LBLOCA) plays a pivotal role in determining the capability of the safety injection system. APR1400 adopts the direct vessel injection (DVI) method for more effective core penetration of the emergency core cooling (ECC) water than the cold leg injection (CLI) method in the OPR1000 (Optimized Power Reactor 1000 MWe). The DVI method turned out to be prone to occasionally lack in efficacious delivery of ECC to the reactor core during the reflood phase of a LBLOCA, however. This study intends to demonstrate a direct vessel inclined injection (DVII) method, one of various ideas with which to maximize the ECC core penetration and to minimize the direct bypass through the break during the reflood phase of a LBLOCA. The 1/7 scaled down THETA (Transient Hydrodynamics Engineering Test Apparatus) tests show that a vertical inclined nozzle angle of the DVII system increases the downward momentum of the injected ECC water by reducing the degree of impingement on the reactor downcomer, whereby lessening the extent of the direct bypass through the break. The proposed method may be combined with other innovative measures with which to ensure an enough thermal margin in the core during the course of a LBLOCA in APR1400. 相似文献
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Effect of water injection on hydrogen generation during severe accident in a 1000 MWe pressurized water reactor was studied.The analyses were carried out with different water injection rates at different core damage stages.The core can be quenched and accident progression can be terminated by water injection at the time before cohesive core debris is formed at lower core region.Hydrogen generation rate decreases with water injection into the core at the peak core temperature of 1700 K,because the core is quenched and reflooded quickly.The water injection at the peak core temperature of 1900 K,the hydrogen generation rate increases at low injection rates of the water,as the core is quenched slowly and the core remains in uncovered condition at high temperatures for a longer time than the situation of high injection rate.At peak core temperature of 2100-2300 K,the Hydrogen generation rate increases by water injection because of the steam serving to the high temperature steam-starved core.Hydrogen generation rate increases significantly after water injection into the core at peak core temperature of 2500 K because of the steam serving to the relocating Zr-U-O mixture.Almost no hydrogen generation can be seen in base case after formation of the molten pool at the lower core region.However,hydrogen is generated if water is injected into the molten pool,because steam serves to the crust supporting the molten pool.Reactor coolant system (RCS) depressurization by opening power operated relief valves has important effect on hydrogen generation.Special attention should be paid to hydrogen generation enhancement caused by RCS depressurization. 相似文献
12.
Sukhpal Singh Ashok Kumar Charanjeet Singh Kulwant Singh Thind Gurmel S. Mudahar 《Annals of Nuclear Energy》2008
The simultaneous variation of gamma ray buildup factors with absorber thickness (up to 6.5 mfp) and total scatter acceptance angle (which is the sum of incidence and exit beam divergence) in the media of high volume flyash concrete and water was studied experimentally using a point isotropic 137Cs source. 相似文献
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The rate theory of void swelling is generalized to incorporate the effect of excess interstitial production resulting from self-ion injection in simulation studies. The swelling rate is shown to be reduced at all temperatures, the fractional reduction being largest in the region where intrinsic recombination of irradiation-induced interstitials and vacancies dominates, provided there is no dislocation recovery at high doses. When such recovery processes are operative, however, the effect of self-ion injection is most important near the peak swelling temperature and can lead to a saturation in swelling with increasing dose which, in the model considered, would be absent under neutron irradiation. For this reason it is emphasized that the results of simulation experiments, without complementary microstructural data, should be viewed with caution as far as their quantitative relation to neutron damage is concerned. 相似文献
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The application of dimensional analysis to the partial penetration data on the Battelle models (1/15 and 2/15 scales) results in a better fit of the penetration data than previous correlations. This analysis predicts the fractional penetration of ECC water into the lower plenum from the water flow rate, liquid subcooling and system pressure, in terms of Froude numbers based on superficial velocities of steam and water. 相似文献
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A computational fluid dynamic (CFD) model for the pressure vessel of the evolutionary pressurized reactor (EPR™) was developed and validated. The aim of this model is the simulation of transients where three-dimensional effects play a strong role, such as boron dilution and main steam line break (MSLB) scenarios. First, a full solid (CAD) model has been built, that includes all details of the reactor pressure vessel (RPV) and the internals which are important for fluid dynamic analyses. The solid model has then been used as basis for the generation of the computational mesh necessary to carry out CFD simulations. Both a hexahedral and a polyhedral mesh have been created. The CFD model has been validated against experimental results of the JULIETTE facility, a 1:5 scaled mock-up of the EPR™ reactor RPV built by AREVA and equipped with advanced instrumentation.The performances of the hexahedral and the polyhedral meshes are investigated in relation to the agreement with experimental data, convergence and CPU requirements. In addition, the effect of the cold-leg swirls on the velocity field inside the RPV is investigated. These swirls mimic the effects of the main coolant recirculation pumps on the flow field at the entrance of the RPV. It is shown that the CFD model is able to capture the shift of the maximum velocity in the downcomer annulus observed in the experimental results. Good qualitative as well as quantitative agreement with the experimental data is achieved. 相似文献
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H. W. Hendel A. C. England D. L. Jassby A. A. Mirin E. B. Nieschmidt 《Journal of Fusion Energy》1986,5(3):231-244
We report measurements of the fusion reaction rate in the Tokamak Fusion Test Reactor (TFTR) covering a wide range of plasma conditions and injected neutral-beam powers up to 6.3 MW. The fusion neutron production rate in beam-injected plasmas decreases slightly with increasing plasma density ne, even though the energy confinement parameter neE generally increases with density. The measurements indicate and Fokker-Planck simulations show that with increasing density the source of fusion neutrons evolves from mainly beam-beam and beam-target reactions at very low ne to a combination of beam-target and thermonuclear reactions at high ne. At a given plasma current, the reduction in neutron source strength at higher ne is due to both a decrease in electron temperature and in beam-beam reaction rate. The Fokker-Planck simulations also show that at low ne, plasma rotation can appreciably reduce the beam-target reaction rate for experiments with coinjection only. The variation of neutron source strength with plasma and beam parameters is as expected for beam-dominated regimes. However, the Fokker-Planck simulations systematically overestimate the measured source strength by a factor of 2–3; the source of this discrepancy has not yet been identified.On leave from RCA David Sarnoff Research Center, Princeton, New Jersey 08540.On assignment from Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831.On leave from Idaho National Engineering Laboratory, EG&G Idaho, Inc., Idaho Falls, Idaho 83415. 相似文献
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Experimental studies on steel corrosion were performed in simulated PBWFR (Pb-Bi cooled direct contact boiling water fast reactor) coolant environment. Some candidate steels of high Cr contents were immersed in steam-injected liquid Pb-Bi pool to investigate how their Cr contents and oxygen potential in Pb-Bi or (PH2/PH2O) in the steam influence their corrosion behaviors at temperature range of the reactor operation. Test specimens were made from eight types of steel with Cr contents ranged from 8 to 18%. The experiments were conducted by exposing these specimens to Pb-Bi pool where steam was injected. (PH2/PH2O) ratios of the steam were employed as experimental parameter, ranged from < 3×10−7 to 1×10−5 to control oxygen potential of Pb-Bi. Exposure temperatures were studied of 400, 450 and 500°C. It was found that 12Cr steel (HCM12/HCM12A) was the most resistant to corrosion and therefore a candidate reactor material. 相似文献
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The present study investigates the effect of free surface motion of a fluid on the dynamic behavior of thin-walled cylindrical shells. This paper outlines a semi-analytical approach to dynamic analysis of a fluid-filled horizontal cylindrical shell taking into account free surface motion; sloshing. The aim of the method is to provide a general approach that can be used for both analysis and synthesis of fluid/structure interaction problems in horizontal cylindrical shells focusing on the dynamic interaction between a flexible structure and incompressible and inviscid flow. The approach is very general; it allows dynamic analysis of both uniform and non-uniform cylindrical shells and considers the fluid forces and includes the sloshing effect exerted on the structure. The hybrid method developed in this work incorporates a combination of the classic finite element approach and thin shell theory to determine the specific displacement functions. Mass and stiffness matrices of the shell are determined by precise analytical integration. A potential function is applied to develop the dynamic pressure due to the fluid. The kinetic and potential energies are evaluated for a range of fluid heights to find the influence of the fluid on the dynamic responses of the structure. The influence of physical and geometrical parameters on the fluid-structure system has been considered in the numerical solutions. When these results are compared with corresponding results available in the literature, both theoretical and experimental, very good agreement is obtained. 相似文献
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