Numerical Investigation of Melt Jet Breakup With Different Shapes in Water Pool

2017 ◽  
Author(s):  
Hui Cheng ◽  
Jiyun Zhao
Keyword(s):  
Surface Area ◽  
Steam Explosion ◽  
Nuclear Power ◽  
3D Model ◽  
Severe Accident ◽  
Interface Surface ◽  
Jet Breakup ◽  
Different Shapes ◽  
Interface Surface Area ◽  
2D Model

During a severe accident in nuclear power plant, core damage may occur due to decay heat and molten fuel can pour into and interact with water resulting in steam explosion. The energetics of steam explosion strongly depends on the initial premixing stage during which the molten fuel undergoes a coarse fragmentation process, which determines the surface area for fuel-coolant contact and heat transfer. Extensive research has been done to understand the premixing stage, however, most of the studies are focused on the cylindrical jet interaction with water. In fact, during core melt, the molten fuel may pour near the edge of core, so the shapes and size of melt jet may differ significantly based on specific conditions. In this paper, numerically study on the melt jet breakup with different shapes in pool water are conducted, such as elliptical shape with VOF method. Firstly, the deformation of molten jet under the same conditions in 2D model is compared with 3D model and shows that the breakup of 3D model is quite different from 2D model, the integration of 3D model is maintained much better than 2D model. Then the characteristics of breakup of elliptic cylindrical melt jet are analyzed and compared with cylindrical melt jet. The results shows that the interface surface area of elliptic cylindrical jet is nearly twice the cylindrical jet.

Numerical Simulation of Corium Jet Breakup During Fuel-Coolant Interaction Based on the ALISA Test Performed at KROTOS Test Facility

2018 ◽  
Author(s):  
Pei Shen ◽  
Wenzhong Zhou
Keyword(s):  
Numerical Simulation ◽  
Steam Explosion ◽  
Field Method ◽  
Severe Accident ◽  
Phase Field Method ◽  
Test Facility ◽  
Jet Breakup ◽  
Jet Behavior ◽  
Jet Fragmentation ◽  
Explosion Test

Steam explosion is one of the consequences of fuel-coolant interactions in a severe accident. Melt jet fragmentation, which is the key phenomenon during steam explosion, has not been clarified sufficiently which prevents the precise prediction of steam explosion. The focus of this paper is on the numerical simulation of the melt jet behavior falling into a coolant pool in order to get a qualitative and quantitative understanding of initial premixing stage of fuel-coolant interaction. The objective of our first phase is the simulation of the fragmentation process and the estimation of the jet breakup length. A commercial CFD code COMSOL is used for the 2D numerical analysis employing the phase field method. The simulation condition is similar to our steam explosion test supported by the ALISA (Access to Large Infrastructure for Severe Accidents) project between European Union and China, and carried out in the KROTOS test facility at CEA, France. The simulation result is in relatively good agreement with the experimental data. Then the effect of the initial jet velocity, the jet diameter and the instability theory are presented. The preliminary data of melt jet fragmentation is helpful to understand the premixing stage of the fuel-coolant interaction.

Development of a Multiphase Particle Method for Melt-Jet Breakup Behavior of Molten Core in Severe Accident

2020 ◽  
Author(s):  
Zidi Wang ◽  
Yuzuru Iwasawa ◽  
Tomoyuki Sugiyama
Keyword(s):  
Nuclear Power ◽  
Particle Method ◽  
Transient Heat Conduction ◽  
Severe Accident ◽  
Lagrangian Description ◽  
Potential Threat ◽  
High Order Scheme ◽  
Containment Vessel ◽  
Jet Breakup ◽  
Solidification Processes

Abstract In a hypothetical severe accident in a light water reactor (LWR) nuclear power plant, there is a possibility that molten core released from the reactor vessel gets in contact with water in the containment vessel. In this so-called fuel-coolant interactions (FCIs) process, the melt jet will breakup into fragments, which is one of the important factors for a steam explosion, as a potential threat to the integrity of the containment vessel. The particle method could directly and easily capture the large deformed interfaces by particle motions, benefiting from its Lagrangian description and meshless framework. In order to investigate the melt-jet breakup with solidification processes, a multiphase particle method with arbitrary high order scheme is presented in this study. In addition, an interfacial particle shifting scheme is developed to suppress the unnatural particle penetration between different phases. The convergence rate with different order is firstly confirmed by a verification test in terms of both explicit and implicit calculations. Then, a transient heat conduction between two materials is carried out and quite good results are obtained. After that, a rising bubble benchmark is performed to show the feasibility of modelling for deformation and collapse. Improvements of clear interface are indicated compared with previous reported results. Two important multiphase instabilities, namely the Rayleigh-Taylor instability and the Kelvin-Helmholtz instability, are studied since they play important roles during the melt-jet breakup. The results achieved so far indicate that the developed particle method is capable to analyze the melt-jet breakup with heat transfer.

Characterization of aluminum/alumina/TiC hybrid composites in 3D produced by anodizing and accumulating roll bonding process using synchrotron radiation tomography

2018 ◽  
Vol 53 (9) ◽  
pp. 1215-1227
Author(s):  
KM Mostafijur Rahman ◽  
Jerzy Szpunar ◽  
Mohammad Reza Toroghinejad ◽  
George Belev
Keyword(s):  
Mechanical Properties ◽  
Synchrotron Radiation ◽  
Surface Area ◽  
Accumulative Roll Bonding ◽  
Hybrid Composites ◽  
Roll Bonding ◽  
Interface Surface ◽  
Area Distribution ◽  
Internal Homogeneity ◽  
Interface Surface Area

Hybrid composites of Al/Al2O3/TiC were produced by anodizing and accumulative roll bonding processes. We implemented 3D imaging of the composites using synchrotron radiation tomography at Biomedical Imaging and Therapy’s 05B1-1 beamline at Canadian Light Source to collect information on internal structure of these hybrid composites i.e. distribution of particles and voids, particle/matrix interface and surface area distribution after different accumulative roll bonding passes. The volume and interface surface area distribution are responsible for strength and toughness of the composites along with other factors such as strain hardening and formation of ultrafine grains. We found that the mechanical properties improved as the number of accumulative roll bonding passes increases and the internal homogeneity of structure also improved. The composites after different accumulative roll bonding passes are studied where the number of reinforced particles and voids and their shape and size distribution were accurately being quantified in 3D to relate with mechanical properties of the composite. Such information should be of importance in analysis and improvement of the manufacturing process of these types of composites.

Two-phase damping and interface surface area in tubes with vertical internal flow

2009 ◽  
Vol 25 (1) ◽  
pp. 178-204 ◽  
Author(s):  
C. Béguin ◽  
F. Anscutter ◽  
A. Ross ◽  
M.J. Pettigrew ◽  
N.W. Mureithi
Keyword(s):  
Surface Area ◽  
Internal Flow ◽  
Two Phase ◽  
Phase Damping ◽  
Interface Surface ◽  
Interface Surface Area

A Proposed Approach for Accurate Estimation of Interface Surface Area in Multiphase Simulations

2020 ◽  
Author(s):  
Simon Peter Shipkowski ◽  
Isaac Perez-Raya ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Growth Rate ◽  
Surface Area ◽  
Bubble Growth ◽  
Volume Fraction ◽  
Superheated Liquid ◽  
Accurate Estimation ◽  
Interface Surface ◽  
Fluid Velocities ◽  
Interface Surface Area

Abstract Multiphase simulations and computational methods with precisely quantified interfaces are important for variety of engineering applications. A few of these applications are: heat transfer utilizing boiling processes, optimizing combustion, and additive printing/deposition processes. In these applications, calculating the length of the interface between two phases (e.g. a vapor and liquid) is particularly critical. Errors in the calculation of the size of the interface propagate over subsequent time steps thereby producing inaccurate rates of phase-change, fluid velocities, and convection heat transfer. This work proposes a method to reduce the reduce error in interface calculations in multiphase simulations. The proposed method uses the interface inclination and the vapor volume-fraction on each computational cell to compute the interface surface area. Moreover, this work provides details on proper declaration and computation of mass transfer with the Volume-of-Fluid sharp interface tracking algorithm. The performance of the proposed approach is compared with the accepted method that estimates interface surface area with gradients of vapor volume fractions. Computer simulations of spherical bubble growth in superheated liquid demonstrate the relevance of the proposed approach. Results indicate that the errors with the accepted method could propagate to 20% (relative to the theoretical estimation) in the prediction of bubble growth rate and fluid velocities. The proposed approach leads to errors of less than 1% in the prediction of bubble growth rate and fluid velocities.

A Dimensional Analysis of Ex-Vessel Steam Explosion

2018 ◽  
Author(s):  
Li Wei ◽  
Guo Qiang ◽  
Yuan Yidan
Keyword(s):  
Data Mining ◽  
Dimensional Analysis ◽  
Steam Explosion ◽  
Nuclear Power ◽  
Power Plants ◽  
Severe Accident ◽  
Dimensionless Parameters ◽  
Experimental Facilities ◽  
Pi Theorem ◽  
Experimental Findings

This paper presents a dimensional analysis for ex-vessel steam explosion occurring in a severe accident of nuclear power plants. Some dimensionless parameters were obtained from this analysis through Buckingham’s PI theorem. These dimensionless parameters are not only helpful to design experimental facilities and testing parameters, but also useful to categorize the experimental findings into uniform forms which facilitate data mining for in-depth understanding and generalization.

Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: (3) Influence by Complicated Structure on Jet Breakup and Fragmentation Behavior

2014 ◽  
Author(s):  
Ryusuke Saito ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Nuclear Power ◽  
Constant Term ◽  
Severe Accident ◽  
Shearing Stress ◽  
Complicated Structure ◽  
Simulation Code ◽  
Fragmentation Behavior ◽  
Jet Breakup ◽  
Image Velocimetry

To estimate the state of Reactor Pressure Vessel (RPV) of Fukushima Daiichi nuclear power plant, it is important to clarify the breakup and the fragmentation behavior of molten material jet in BWR lower plenum by a numerical simulation. To clarify the effects of complicated structures on jet breakup and fragmentation behavior experimentally and construct the benchmarks of the simulation code, we conduct the visualized experiments simulating the severe accident in the BWR. In this study, the jet breakup behavior, the fragmentation behavior and internal/external velocity profiles of the jet were observed by the backlight method and the particle image velocimetry (PIV). From experimental results, it is clarified that the complicated structures prolong the jet breakup length or make the fragments fallen together to the lower plenum similar to the bulk state. In addition, it is clarified that strong shearing stress occurs at the crest of interfacial waves at side of the jet when fragments are generated. Finally, the fragment diameters measured in the present study well agree with the theory suggested by Kataoka et al. (1983) by changing the coefficient term at each experimental condition. Thus, it is suggested that the fragmentation mechanism is mainly controlled by shearing stress and the fragment diameter can be estimated by adjusting the constant term.

Two-Phase Damping and Interface Surface Area in Tubes With Internal Flow

2006 ◽  
Author(s):  
Franc¸ois Anscutter ◽  
Ce´dric Be´guin ◽  
Annie Ross ◽  
Michel J. Pettigrew ◽  
Njuki W. Mureithi
Keyword(s):  
Flow Regime ◽  
Surface Area ◽  
Bubbly Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Spherical Bubble ◽  
Phase Damping ◽  
Interface Surface ◽  
Interface Surface Area ◽  
Churn Flow

Two-phase flow is common in the nuclear industry. It is a potential source of vibration in piping systems. In this paper, two-phase damping in the bubbly flow regime is related to the interface surface area between phases and, therefore, to flow configuration. Two sets of experiments were performed with a vertical tube clamped at both ends. First, gas bubbles of controlled geometry were simulated with glass spheres let to settle in stagnant water. Second, air was injected in stagnant alcohol to generate a uniform and measurable bubble flow. In both cases, the two-phase damping ratio is correlated to the number of bubbles (or spheres). Two-phase damping is directly related to the interface surface area, based on a spherical bubble model. Further experiments were carried out on tubes with internal two-phase air-water flows. A strong dependence of two-phase damping on flow configuration in bubbly flow regime is observed. A series of photographs attests to the fact that two-phase damping increases for a larger number of bubbles, and for smaller bubbles. It is highest immediately prior to the transition from bubbly flow to slug or churn flow regimes. Beyond the transition, damping decreases. An analytical model is proposed to predict two-phase flow damping in bubbly flow, based on a spherical bubble model. The results also reveal that the transition between bubbly flow and slug/churn flow depends on tube diameter. Consequently, the tube diameter also has an effect on two-phase damping. The above results could lead to some modifications of existing flow regime maps for small diameter tubes.

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