Influence of the Fragmentation Behavior on Molten Material Jet Breakup in Coolant

2013 ◽  
Author(s):  
Yuzuru Iwasawa ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Taihei Kuroda ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
High Speed ◽  
Density Ratio ◽  
Heat Removal ◽  
Free Fall ◽  
Core Material ◽  
Dominant Factor ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

For the safety design of a Fast Breeder Reactor (FBR), Post Accident Heat Removal (PAHR) is required when a hypothetical Core Disruptive Accident (CDA) occurs. In PAHR, it is strongly required that the molten core material can be solidified and cooled down by the sodium coolant in a reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant, it is necessary to understand the interaction between the molten core material and the coolant. The objective of the present study is to clarify the dominant factor of the jet breakup length and the size of the fragments experimentally. In this study, we injected molten material (Sn–Bi alloy) into coolant (water) at free fall speed. We can simulate an actual FBR system by using Sn-Bi alloy and water because the density ratio of them is similar to that of an actual FBR system. The jet breakup and the fragmentation behavior of the molten material jet were observed with a high speed video camera. In the previous study which we conducted, solidified crust is generated by the solidification on the molten material jet surface and affects the jet breakup and the fragmentation behavior. Then from the experimental results, in order to predict the size of fragments, it is constructed that the instability model based on hydrodynamic and material mechanics. Then in this paper, the surface close-up of the molten material jet was observed in order to investigate the effect of the solidification on the molten material jet surface.

Visual Observation of Fragmentation Behavior on Molten Material Jet Surface in Coolant

2008 ◽  
Author(s):  
Yuta Uchiyama ◽  
Yutaka Abe ◽  
Akiko Fujiwara ◽  
Hideki Nariai ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
Water Surface ◽  
High Speed ◽  
Internal Flow ◽  
Core Material ◽  
Generation Process ◽  
High Speed Camera ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

For the safety design of the Fast Breeder Reactor (FBR), it is strongly required that the post accident heat removal (PAHR) is achieved after a postulated core disruptive accident (CDA). In the PAHR, it is important that the molten core material is solidified in sodium coolant which has high boiling point. Thus it is necessary to estimate the jet breakup length which is the distance that the molten core material is solidified in sodium coolant. In the previous studies (Abe et al., 2006), it is observed that the jet is broken up with fragmenting in water coolant by using simulated core material. It is pointed out that the jet breakup behavior is significantly influenced by the fragmentation behavior on the molten material jet surface in the coolant. However, the relation between the jet breakup behavior and fragmentation on the jet surface during a CDA for a FBR is not elucidated in detail yet. The objective of the present study is to elucidate the influence of the internal flow in the jet and fragmentation behavior on the jet breakup behavior. The Fluorinert™ (FC-3283) which is heavier than water and is transparent fluid is used as the simulant material of the core material. It is injected into the water as the coolant. The jet breakup behavior of the Fluorinert™ is observed by high speed camera to obtain the fragmentation behavior on the molten material jet surface in coolant in detail. To be cleared the effect of the internal flow of jet and the surrounding flow structure on the fragmentation behavior, the velocity distribution of internal flow of the jet is measured by PIV (Particle Image Velocimetry) technique with high speed camera. From the obtained images, unstable interfacial wave is confirmed at upstream of the jet surface, and the wave grows along the jet-water surface in the flow direction. The fragments are torn apart at the end of developed wave. By using PIV analysis, the velocity at the center of the jet is fast and it suddenly decreases near the jet surface. This means that the shear force acts on the jet and water surface. From the results of experiment, the correlation between the interfacial behavior of the jet and the generation process of fragments are discussed. In addition, the influence of surface instability of the jet induced by the relative velocity between Fluorinert™ and coolant water on the breakup behavior is also discussed.

Experimental Study on Jet Breakup Behavior With Surface Solidification

2010 ◽  
Author(s):  
Takashi Wada ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Yuta Uchiyama ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Size Distribution ◽  
Reactor Vessel ◽  
Image Processing Technique ◽  
Core Material ◽  
Dominant Factor ◽  
Sodium Coolant ◽  
Molten Material ◽  
Breakup Length ◽  
Jet Breakup ◽  
Median Diameter

For the safety design of the Fast Breeder Reactor (FBR), the Post Accident Heat Removal (PAHR) is required when a hypothetical Core Disruptive Accident (CDA) occurs. In the PAHR, it is strongly required that the molten core material can be cooled down and solidified by the sodium coolant in the reactor vessel. There is high possibility for molten material to be ejected as a liquid jet into sodium coolant in the reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant or not, it is necessary to understand the interaction between molten core material and coolant such as jet breakup and fragmentation behavior in coolant. The jet breakup behavior is the phenomenon that the front of molten material breaks up in coolant. To clarify the mechanism of jet breakup and fragmentation during the CDA for the FBR, it is necessary to understand the correlation between jet breakup lengths and size distribution of fragments when molten material jet interacting with coolant. The objective of the present study is to clarify the dominant factor of the jet breakup length and the size distribution of fragments experimentally. Molten jet of U-alloy 138 is injected into water as simulated core material and coolant by free-fall. The density ratio of core material and coolant is almost same as that of the real FBR system. The jet breakup behavior as interaction of molten material with coolant is observed with high speed video camera. Front velocity of the molten material jet is estimated by using the image processing technique. It suddenly decreases when the jet fall into the coolant. The jet breakup length estimated from observed images is compared with the breakup theories to understand the effect of experimental parameters for the jet breakup length. The solidified fragments are gathered and classified in size, and the mass in each size is measured. Median diameter is obtained from the mass distribution of the fragments. In comparison with interfacial instabilities, the median diameter of fragments shows the independent of relative velocity. The jet breakup lengths and median diameters compared with existing theories is discussed.

Jet Breakup Behavior With Surface Solidification

2012 ◽  
Author(s):  
Yuzuru Iwasawa ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Taihei Kuroda ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
Reactor Vessel ◽  
Core Material ◽  
Material Strength ◽  
Fast Breeder Reactor ◽  
Numerical Estimation ◽  
Sodium Coolant ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup ◽  
Mass Median

When a hypothetical Core Disruptive Accident (CDA) occurs in Fast Breeder Reactor (FBR), it is strongly required that the molten core material can be solidified and cooled down by the sodium coolant in a reactor vessel. In order to estimate whether the molten material jet is completely solidified by sodium coolant, it is necessary to understand the interaction between the molten core material and the coolant. The objectives of the present study are to clarify the correlation of the jet breakup and fragmentation behavior and the dominant factors of both behaviors considering surface solidification. In order to investigate the influence of surface solidification on jet breakup and fragmentation behavior, experiments under surface solidification and liquid-liquid contact condition are conducted. Although the molten material jet is fragmented with each condition, jet breakup and fragmentation behaviors on each condition are different. In addition, when the surface solidification occurs, there is possibility that the material strength of solidified crust on the surface affects jet breakup and fragmentation behaviors. Then, numerical calculation based on hydrodynamics and material mechanics is conducted to evaluate the influence of the material strength on jet breakup and fragmentation behaviors. In comparison with the numerical estimation and mass median diameters obtained from experimental results, the effect of solidification on jet breakup and fragmentation behavior of molten material jet is discussed.

Influence of Hydrodynamic Interaction on Jet Breakup and Fragmentation Behavior

2014 ◽  
Author(s):  
Shimpei Saito ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Yuzuru Iwasawa ◽  
Eiji Matsuo ◽  
...  
Keyword(s):  
High Speed ◽  
Hydrodynamic Interaction ◽  
Heat Removal ◽  
Leading Edge ◽  
Air Entrainment ◽  
Video Camera ◽  
Liquid System ◽  
Core Material ◽  
Edge Region ◽  
Jet Breakup

Mitigative measures against a Core Disruptive Accident (CDA) are important from the viewpoints of safety of a Fast Breeder Reactor (FBR). If a CDA occurs, Post Accident Heat Removal (PAHR) must be surely achieved. In the PAHR, molten materials are likely to be injected into the coolant like a jet and they must satisfy two requests simultaneously: fast ejection and stable cooling after quenched. In order to estimate the quench behavior of the molten jet, it is important to understand how the jet breaks up. The objective of this study is to clarify that the influence of hydrodynamic interaction between a jet and the surrounding fluid on jet breakup. Previous works have clarified that one cause of the jet breakup is provoked by fragmentation at the side of a jet. However, there are few detailed results describing the correlation between jet breakup and hydrodynamic interaction at the leading-edge region of a jet. Additionally, air entrainment with a jet is always observed in our past experiments using simulants, but its influence has not been discussed yet. In this study, jet injection experiments in liquid-liquid system were conducted for investigating the interaction a jet and an ambient fluid, and the effect of air entrainment on jet breakup behavior. Both simulant core materials and coolants were transparent liquids for visualization. The stored simulant core material was injected into a tank filled with the simulant coolant. In order to realize the condition without air entrainment, the air remaining within the nozzle was removed using a syringe. The jet breakup behavior was observed with a high speed video camera. A normal backlight system and a Laser Induced Fluorescence (LIF) system were employed for visualization. The inner velocity distribution of a jet was measured by Particle Image Velocimetry (PIV). As a result, in the experiments without air entrainment the jet breakup lengths were described by Epstein’s equation. In addition, a pair of vortices was observed at the leading-edge region. The vortices were generated at the leading edge and the leading edge rolled up by the vortices returned toward a jet core. Thus, it was very likely that the vortices at the leading edge region promoted jet breakup.

Effect of Solidification on Molten Material Jet Behavior in Coolant

2014 ◽  
Author(s):  
Yuzuru Iwasawa ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Shimpei Saito ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Melting Point ◽  
Energy Release ◽  
High Speed ◽  
Heat Removal ◽  
Injection Velocity ◽  
Molten Material ◽  
Breakup Length ◽  
Jet Breakup ◽  
Jet Behavior ◽  
Interfacial Temperature

For the safety design of a Fast Breeder Reactor (FBR), if a Core Disruptive Accident (CDA) occurred hypothetically, it is required to suppress the rapid energy release due to a prompt criticality. Even if the rapid energy release does not occur, there is a possibility that a large amount of fuel melts. Therefore it is important to achieve Post Accident Heat Removal (PAHR). In order to achieve PAHR, it is strongly required that the molten material which is released from a core region gets cool and solidifies in the sodium coolant in a reactor vessel by breaking up. It is considered that the molten fuel is injected into the coolant like a jet. Furthermore, in the actual FBR, the interfacial temperature between the molten fuel jet and the coolant is considered to be lower than the melting point of the molten material. Thus for PAHR in CDA, it is important to understand the interaction between the jet and the coolant in such a condition and to estimate the molten jet behavior quantitatively. In order to estimate quantitatively the effects of the solidification on the molten jet behavior, we carried out the experiment in which a simulant material was injected into a simulant coolant. In the experiment, we used low melting point alloy (Bi -Sn) and water as the simulant molten material and the simulant coolant respectively. In the experiments, we chose the temperature range including the condition that the interfacial temperature was lower than the melting point of the molten material. The jet breakup and the fragmentation behavior of the molten material jet were observed with a high speed video camera. Then the jet breakup length is estimated form the results. We changed the initial interfacial temperature condition by adjusting temperature of the molten material and the coolant. We also changed the jet velocity by adjusting the height of the nozzle tip from the water surface. From the experiment, we found that the jet breakup behavior depends greatly on the interfacial temperature and the injection velocity and that the solidification of a molten material jet and the growth of unstable jet surface, which results from the relative velocity of the jet to the coolant, are in a competitive relation for the jet breakup. We also found that when the molten material jet breaks up into fragments, the breakup length is independent of the initial interfacial temperature and the initial injection velocity.

Estimation of Fragmentation on Jet Breakup in Coolant

2012 ◽  
Author(s):  
Taihei Kuroda ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Iwasawa Yuzuru ◽  
Hideki Nariai ◽  
...  
Keyword(s):  
Flow Field ◽  
Tap Water ◽  
Energy Ratio ◽  
Liquid Jet ◽  
Sodium Coolant ◽  
Molten Material ◽  
Colorless Liquid ◽  
Fragmentation Behavior ◽  
Breakup Length ◽  
Jet Breakup

Fast Breeder Reactor (FBR) is designed with safety in mind. However, there is billion to one possibility that a hypothetical Core Disruptive Accident (CDA) occurs. When CDA occurs, the Post Accident Heat Removal (PAHR) must be achieved. In the PAHR, the molten material is required to be fragmented and solidified in sodium coolant. In order to estimate whether the molten material jet is completely solidified in sodium coolant or not, it is significant to estimate jet breakup length. Although, the jet breakup length is influenced with fragmentation behavior, the correlation between them is not clear yet. Therefore, it is strongly required to clarify the mechanism of the fragmentation behavior on the jet surface. The objective of the present study is to estimate fragmentation on jet breakup in coolant experimentally. Tap water and Fluorinert™ (FC-3283) are used as simulated coolant and molten material, respectively. Flourinert is transparent and colorless liquid and its density is higher than water, therefore we can observe internal flow structure of Fluorinert. Fluorinert injected into water, and the jet breakup behavior and the fragmentation behavior of the jet are observed by using high speed video camera. In order to estimate fragmentation on liquid jet, we identified the position of the interface with back lighting technique and also, we conducted velocity measurement with Particle Image Velocimetry (PIV) technique simultaneously. It is observed that interfacial waves of the jet are generated. Waves are pulled with surrounding liquid and grown up. Finally, a fragment is separated as a droplet from front edge of the wave. Also, the vorticity is evaluated from the velocity data in order to investigate influence of the flow field in detail. From the result of calculating vorticity, the high value was estimated when jet was fragmented. It is suggested that fragmentation behavior correlates with the surrounding flow field. And the energy ratio contributing to fragmentation is calculated from velocity field. The energy ratio is important to investigate the amount of the fragmentation on liquid jet. Fragmentation on jet breakup in coolant is estimated.

Study on the Interaction of Molten Metal and a Coolant

2002 ◽  
Author(s):  
Tetsuya Kizu ◽  
Yutaka Abe ◽  
Hideki Nariai ◽  
Keiko Chitose ◽  
Kazuya Koyama
Keyword(s):  
Molten Metal ◽  
Heat Removal ◽  
Reactor Vessel ◽  
Core Material ◽  
Fast Breeder Reactor ◽  
Molten Material ◽  
Two Phase ◽  
Metal Jet ◽  
Two Phase Cooling

In a core disruptive accident (CDA) of a fast breeder reactor, the post accident heat removal (PAHR) is crucial for the accident mitigation. The molten core material should be cooled by the inventory of the coolant in the lower plenum of the reactor vessel. It is still unknown whether two phase cooling can be expected during molten core material and coolant interaction. The purpose of the present study is to experimentally clarify the cooling capability of the coolant for the molten material including two phase boiling. In the experiment, simulated molten metal jet is injected into water to experimentally obtain the visualized information of the fragmentation and boiling phenomena during PAHR in CDA.

20812 Influence of Fragmentation Behavior on Molten Material Jet Breakup

2013 ◽  
Vol 2013.19 (0) ◽  
pp. 419-420
Author(s):  
Yuzuru IWASAWA ◽  
Yutaka ABE ◽  
Akiko KANEKO ◽  
TAIHEI Kuroda ◽  
Eiji MATSUO ◽  
...  
Keyword(s):  
Molten Material ◽  
Fragmentation Behavior ◽  
Jet Breakup

Atomization and Droplet Dispersion of Low-Momentum Water Jet by High-Speed Crossflow Air Stream

2010 ◽  
Author(s):  
Cuicui Liu ◽  
Zeyi Jiang ◽  
Huafei Liu ◽  
Xinxin Zhang ◽  
Shunhua Xiang
Keyword(s):  
Group Velocity ◽  
High Speed ◽  
Water Jet ◽  
Spray Angle ◽  
Dominant Factor ◽  
Sauter Mean Diameter ◽  
Droplet Dispersion ◽  
Jet Breakup ◽  
Air Stream ◽  
Mean Diameter

In this paper, a low-momentum water liquid jet emanating transversely into a high-speed air stream is investigated analytically and numerically. Viscous instability followed by Rayleigh-Taylor instability is used in the jet breakup analysis to obtain the Sauter Mean Diameter and the droplet group velocity after the breakup. With the analytical results, droplet dispersion in the air stream is simulated by the coupled Eulerian-Lagrangian approach, in which the root-normal distribution is adopted to represent the droplet diameter distribution. Water flux distribution and spray angle are obtained and validated by experimental data. The results show that the air velocity is a dominant factor on the Sauter Mean Diameter and droplet group velocity in the water jet breakup process and the spray angle is influenced by the water mass flux.

Experimental Study on Influence of Interfacial Behavior on Jet Surface Fragmentation

2009 ◽  
Author(s):  
Yuta Uchiyama ◽  
Yutaka Abe ◽  
Akiko Kaneko ◽  
Hideki Nariai ◽  
Makoto Yamagishi ◽  
...  
Keyword(s):  
Shear Stress ◽  
Interfacial Behavior ◽  
Interfacial Wave ◽  
Molten Material ◽  
Fragmentation Behavior ◽  
Breakup Length ◽  
Piv Technique ◽  
Jet Breakup ◽  
Local Shear ◽  
Local Shear Stress

For the safety design of the Fast Breeder Reactor (FBR), it is strongly required that the Post Accident Heat Removal (PAHR) is achieved after a hypothetical Core Disruptive Accident (CDA). In the PAHR, it is important that the molten material is fragmented to be solidified by the sodium coolant with high boiling point and thermal conductivity. Furthermore, in order to estimate whether the molten material jet is completely solidified in sodium coolant or not, it is necessary to evaluate the jet breakup length. Although there are many previous studies on the jet breakup length, the tendency of jet breakup length is different for the previous studies. To estimate jet breakup length, it is necessary to understand the interaction between molten core material and coolant. The objective of the present study is to clarify the influence of the interfacial behavior of the jet on the fragmentation behavior on the jet surface. The experiments are conducted to obtain the interfacial behavior and the fragmentation behavior on the jet surface by injecting transparent Fluorinert™ (FC-3283) into water. The jet breakup behavior of the Fluorinert and the fragmentation behavior on the jet surface in pool are observed by using high speed video camera. To clarify the influence of interfacial behavior on jet surface fragmentation, it is necessary to clarify the effect of the internal flow of the jet and the surrounding flow structure on the interfacial behavior. The internal and the external velocity distribution of the jet are obtained by Particle Image Velocimetry (PIV) technique from the visual data. Shear stress is evaluated from the velocity data obtained by PIV technique. Reynolds stress and turbulent energy are also evaluated from the velocity data. As the results, shear stress becomes large along the interfacial wave. The maximum value of shear stress is decreased toward downstream. Reynolds stress becomes large at the jet surface. The vortex around the interfacial wave is observed by PIV measurement. The local shear stress acts on the interfacial wave. It is suggested that the local shear stress on the jet surface causes the fragmentation. From the experimental results, the interaction between the interfacial behavior of the jet and flow structure of the jet and surrounding fluid are discussed. The dominant mechanism of the fragmentation behavior and the influence of local shear stress at the interface on the fragementation are also discussed.

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