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.

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 Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: 1 — Preliminary Analysis of Jet Breakup Behavior in Complicated Structure by TPFIT

2013 ◽  
Author(s):  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
Fumihisa Nagase ◽  
Yutaka Abe ◽  
Akiko Kaneko
Keyword(s):  
High Speed ◽  
Measured Data ◽  
Severe Accident ◽  
Interface Tracking ◽  
Phase Flow ◽  
Complicated Structure ◽  
Support Plate ◽  
Jet Breakup ◽  
Multi Phase ◽  
Developing Method

In order to improve the safety of Boiling Water Reactor (BWR), it is required to know the behavior of the plant when an accident occurred as can be seen at Fukushima Daiichi nuclear power plant accident. Especially, it is important to estimate the behavior of molten core jet in the lower part of the containment vessel at severe accident. In the BWR lower plenum, the flow characteristics of molten core jet are affected by many complicated structures, such as control rod guide tubes, instrument guide tubes and core support plate. However, it is difficult to evaluate these effects on molten core jet experimentally. Therefore, we considered that multi-phase computational fluid dynamics approach is the best way to estimate the effects on molten core jet by complicated structure. The objective of this study is to develop the evaluation method for the flow characteristic of molten core jet including the effects of the complicated structures in the lower plenum. So we are developing a simulation method to estimate the behavior of molten core jet falling down through the core support plate to the lower plenum of the BWR. The method has been developed based on interface tracking method code TPFIT (Two Phase Flow simulation code with Interface Tracking). To verify and validate the applicability of the developed method in detail, it is necessary to obtain the experimental data that can be compared with detailed numerical results by the TPFIT. Thus, in this study, we are carrying out experimental works by use of multi-phase flow visualization technique. In the experiments, time series of interface shapes are observed by high speed camera and velocity profiles in/out of the jet will be measured by the PIV method. In this paper, the outline of the developing method based on the TPFIT was explained. And, the developing method was applied to preliminary experiment with/without modeled complicated structures. As the results, predicted interface shapes were almost agreed with measured data. However, predicted falling down velocity of the jet was lower than measured data. We considered causes of this underestimation and improved the method and simulation conditions to resolve this problem.

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.

Numerical Simulation of Liquid Jet Behavior in Shallow Pool by Interface Tracking Method

2020 ◽  
Author(s):  
Takayuki Suzuki ◽  
Hiroyuki Yoshida ◽  
Naoki Horiguchi ◽  
Sota Yamamura ◽  
Yutaka Abe
Keyword(s):  
Numerical Simulation ◽  
Hydrodynamic Interaction ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Water Pool ◽  
Molten Material ◽  
Jet Breakup ◽  
Jet Behavior ◽  
Lattice Resolution ◽  
Core Materials

Abstract In the severe accident (SA) of nuclear reactors, fuel and components melt, and melted materials fall to a lower part of a reactor vessel. In the lower part of a reactor vessel, in some sections of the SAs, it is considered that there is a water pool. Then, the melted core materials fall into a water pool in the lower plenum as a jet. The molten material jet is broken up, and heat transfer between molten material and coolant may occur. This process is called a fuel-coolant interaction (FCI). FCI is one of the important phenomena to consider the coolability and distribution of core materials. In this study, the numerical simulation of jet breakup phenomena with a shallow pool was performed by using the developed method (TPFIT). We try to understand the hydrodynamic interaction under various, such as penetration, reach to the bottom, spread, accumulation of the molten material jet. Also, we evaluated a detailed jet spread behavior and examined the influence of lattice resolution and the contact angle. Furthermore, the diameters of atomized droplets were evaluated by using numerical simulation data.

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.

Experimental and Numerical Simulation on Hydraulic Behavior of Molten Flow in the Lower Part in Reactor Core

2016 ◽  
Author(s):  
Kota Matsuura ◽  
Hideaki Monji ◽  
Susumu Yamashita ◽  
Hiroyuki Yoshida
Keyword(s):  
Numerical Simulation ◽  
Liquid Film ◽  
High Speed ◽  
Nuclear Power ◽  
Power Plants ◽  
Flow Behavior ◽  
Reactor Core ◽  
Video Camera ◽  
Working Fluid ◽  
Simulation Code

In the decommissioning work of nuclear power plants, it is important to grasp the sedimentation place of molten materials. However, the technique to grasp exactly sedimentation place is not established now. Therefore, the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior is developed. In the study, visualization experiment and numerical simulation were performed to validate the applicability of the JUPITER to the hydraulic relocation behavior in core internals. The test section used in this experiment simulated the structure of the core internals, such as a control rod and a fuel support piece, simply. The working fluid is water under the atmospheric pressure. The experiment uses a high-speed video camera to visualize the flow behavior. The behavior and the speed of the liquid film in a narrow flow channel is obtained. For the numerical analysis carried out prior to the experiment, the behavior of flow down liquid was shown. The typical behavior was also observed that the tip of a liquid film flowing down splits into.

Liquid Film Flow on Vertical and Successive Inclined Plate Modeling Flow Channel of Molten Control Rod in Severe Accident

2018 ◽  
Author(s):  
Yutaro Hihara ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
Susumu Yamashita ◽  
Hiroyuki Yoshida
Keyword(s):  
Numerical Simulation ◽  
Liquid Film ◽  
Nuclear Reactor ◽  
Flow Channel ◽  
Severe Accident ◽  
Inclined Plate ◽  
Basic Study ◽  
Simulation Code ◽  
Energy Agency ◽  
Modeling Flow

When a severe accident of a nuclear reactor occurs, decommissioning work becomes important task. In the decommissioning work of a boiling water reactor after the severe accident, estimation of the sedimentation place of the molten debris is important. However, the technique to estimate exactly the sedimentation place has not been enough developed. Therefore, the detailed and phenomenological numerical simulation code named “JUPITER” is under development for predicting the molten core behavior in JAEA (Japan Atomic Energy Agency). The comparison between experimental and numerical results is necessary to clarify the validity of the numerical analysis code. The study provides the experimental data to examine the numerical simulation code. As a basic study to examine the numerical simulation code, a liquid film flowing in a modeling flow channel was studied by using water. The flow was visualized, and the flow data were obtained by image processing.

Behavior of Simulated Molten Metal at Channel Modeled Boiling Water Reactors

2017 ◽  
Author(s):  
Yutaro Hihara ◽  
Kota Matsuura ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Analysis ◽  
Molten Metal ◽  
Numerical Results ◽  
Boiling Water ◽  
Severe Accident ◽  
Boiling Water Reactors ◽  
Simulation Code ◽  
Water Reactors

When a severe accident occurs, decommissioning work becomes important task. In the decommissioning work after the severe accident, establishing the way to estimate the sedimentation place of molten debris is important. However, the technique to estimate exactly sedimentation place has not been enough. Therefore, the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior is under development. The comparison between experimental and numerical results is necessary to clarify the validity of the numerical analysis code. This study provides the experimental data for a BWR to examine the numerical simulation code in order to contribute to progress of the decommissioning work.

Development of Numerical Simulation Method for Melt Relocation Behavior in Nuclear Reactors: Validation of Applicability for Actual Core Support Structures

2016 ◽  
Author(s):  
Susumu Yamashita ◽  
Kazuyuki Tokushima ◽  
Masaki Kurata ◽  
Kazuyuki Takase ◽  
Hiroyuki Yoshida
Keyword(s):  
Numerical Simulation ◽  
High Temperature ◽  
Computer Aided Design ◽  
Nuclear Power ◽  
Radiation Heat Transfer ◽  
Three Dimensional ◽  
Simulation Models ◽  
Simulation Method ◽  
Transfer Model ◽  
Simulation Code

In order to precisely investigate molten core relocation behavior in the Fukushima Daiichi nuclear power station, we have developed the detailed and phenomenological numerical simulation code named JUPITER for predicting the molten core behavior including solidification and relocation based on the three-dimensional multiphase thermal-hydraulic simulation models. At the moment, multicomponent analysis method which can be treated any number of component as a fluid or solid body, Zr-water reaction model and simple radiation heat transfer model were implemented and showed that multicomponent melt flow and its solidification were confirmed in the simplified core structure system. However, the validation of the JUPITER using high temperature molten material has not been performed yet. In this paper, in order to evaluate the validity of the JUPITER, especially, for high temperature melt relocation experiment, we compared between numerical and experimental results for that system. As a result, qualitatively reasonable result was obtained. And also we performed melt relocation simulation on actual core structures designed by three dimensional CAD (Computer-Aided Design) and then we estimated phenomena which might be actually occurred in SAs.

The Development and Application of PWR Severe Accident Simulation Model

2013 ◽  
Author(s):  
Yanfang Chen ◽  
Zhengquan Xie ◽  
Xusheng Lin ◽  
Fuchang Shan ◽  
Wei Wei ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Mathematical Models ◽  
Simulation Model ◽  
Nuclear Power ◽  
Severe Accident ◽  
Plant Type ◽  
Simulation Code ◽  
Accident Simulation ◽  
Simulation Codes

The severe accident simulation codes that developed by the engineers in RINPO are introduced in this chapter. The results of the severe accident caused by large LOCA plus losing safety core injection are presented. Comparison with the results of SCDAP/RELAP5/MOD3.2 of the same accident and the same nuclear power plant type has been made. From the comparison and the analysis we can make the conclusion that the trend-lines are correct and the mathematical models are reasonable in this simulation code.

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