Effect of Deformation of Core Elements of Fast Reactor Core to the Seismic Response

2019 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Shinichiro Matsubara ◽  
Kazuteru Kawamura ◽  
Hidenori Harada ◽  
Tomohiko Yamamoto
Keyword(s):  
Thermal Expansion ◽  
Fast Reactor ◽  
Seismic Analysis ◽  
Three Dimensional ◽  
Reactor Core ◽  
Axial Direction ◽  
Vertical Displacement ◽  
Analysis Model ◽  
The Core ◽  
Core Elements

Abstract Core elements of a fast reactor are self-standing on the core support structure and not restrained in the axial direction. When the earthquake occurs, it is necessary to consider vertical behavior and horizontal displacement of the core elements simultaneously. In the core seismic analysis, a three dimensional core vibration behavior was evaluated by considering fluid structure interaction, collision with adjacent core elements and vertical displacement and verified by a series of vibration tests. But the evaluation had a assumption of straightness of each core elements which may be bowed due to thermal expansion and swelling under restraint of the horizontal direction between the upper pad and lower structure (Entrance Nozzle). If the core elements are deformed in its plant operation, they may push each other against its adjacent core elements. The large horizontal interference forces may work to decrease the vertical displacement of the core elements. In this study, to grasp and estimate the behavior under the deformed core elements under the earthquake motion, a three dimensional seismic analysis model consist of all of core elements with consideration of the effect of deformed core elements were prepared, analyzed and verified by hexagonal-matrix tests with 37 core elements and single row mock-up models with 7 core elements. These test results show that the rising displacements decrease with increased deformation and no rising occurs when the deformations exceed a threshold. In this paper, the effect of bending deformation due to thermal expansion and swelling on the rising displacement of the core elements was shown by seismic experiments.

Fast Reactor Core Seismic Analysis for Verification of Assessment Model Considering Deformation of Core Elements

2019 ◽  
Author(s):  
Shinichiro Matsubara ◽  
Akihisa Iwasaki ◽  
Kazuteru Kawamura ◽  
Hidenori Harada ◽  
Tomohiko Yamamoto
Keyword(s):  
Fast Reactor ◽  
Seismic Analysis ◽  
Evaluation Model ◽  
Reactor Core ◽  
Vertical Displacement ◽  
Core Element ◽  
Structure Interaction ◽  
The Core ◽  
Core Elements ◽  
Vertical Displacements

Abstract To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Thus, a core seismic analysis method has been developed to evaluate 3D core vibration behavior considering fluid structure interaction and vertical displacements (rising). The analysis code is verified by a series of vibration tests. The evaluation model to simulate the influence of core element deformation due to heat and irradiation were developed and the analysis of the seismic test was performed. And the evaluation model was verified by comparing the seismic test and analysis results. A fast reactor core consists of hundreds of core elements, which lengthen due to thermal expansion and swelling. So, the core elements are self-standing on the core support structure and not restrained in the axial direction. When the vertical seismic excitation surpasses gravitational acceleration, it is necessary to consider vertical displacements and horizontal displacements of the core elements simultaneously. This 3-D vibration behavior is affected by the fluid loads from ambient coolant and the interference of surrounding structures. To solve this, the influential factors to vibration behaviors due to the structure and fluid body, including fluid structure interaction, are extracted and the 3-D reactor core group vibration analysis code (REVIAN-3D) is developed. Core elements are deformed due to thermal expansion and irradiation, and are interfered with surrounding elements each other. The interference increases the frictional force acting on the core element and reduce the vertical displacement (rising) of the core element during the earthquake. To evaluate this reduction of rising, the evaluation model simulating this deformation is incorporated in REVIAN-3D. In this study, the analysis of the vibration test was carried out using the new incorporated evaluation model. As the deformation of mock-up increases, the vertical displacement (rising) decreases, and when the initial interference due to deformation exceeds the threshold, no rising occurs. This trend agreed well between the vibration test and analysis. It is verified that the new incorporated evaluation model simulates the test result enough.

Analysis of Seismic Experiment of Hexagonal Multi Bundle Model Using Core Assembly Mock-Up

2020 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Shinichiro Matsubara ◽  
Hidenori Harada ◽  
Tomohiko Yamamoto
Keyword(s):  
Fast Reactor ◽  
Three Dimensional ◽  
Reactor Core ◽  
Vertical Direction ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
The Core ◽  
Vibration Behavior ◽  
Seismic Experiment ◽  
Core Elements

Abstract The fast reactor core is composed of hundreds of core elements that stand independently on the core support plate, but does not have support to constrain vertical displacement in order to avoid effects such as thermal elongation. When the earthquake occurs, the group vibration behavior is shown, including the rising of core elements in vertical direction, the collision with adjacent core elements in horizontal direction, and the fluid structure interaction. The three dimensional core group vibration analysis code (REVIAN-3D) was constructed to evaluate them. In the case of fast reactor cores in Japan, the horizontal displacement of core elements at the outermost periphery is restricted by the core former (core barrel). However, since there is no core former in fast reactors other than Japan and the boundary conditions are different from those in Japan, the vibration behavior also differs. In this study, to grasp and estimate the group vibration behavior with and without a core former under the earthquake motion, seismic experiment of hexagonal multi bundle model using core assembly mock-up was conducted [1]. These test results show that the horizontal displacements are larger and impact force between pads of core assembly mock-up is smaller without the core former. In this paper, the analysis was verified by group vibration tests with and without a core former.

Experimental Study on the Effect of Core Support Frame on Seismic Behavior of Fast Reactor Core

2020 ◽  
Author(s):  
Shinichiro Matsubara ◽  
Akihisa Iwasaki ◽  
Hidenori Harada ◽  
Tomohiko Yamamoto
Keyword(s):  
Fast Reactor ◽  
Three Dimensional ◽  
Reactor Core ◽  
Vertical Direction ◽  
Vertical Displacement ◽  
Test Results ◽  
Core Element ◽  
Vibration Behavior ◽  
Seismic Experiment ◽  
Core Elements

Abstract The fast reactor core is composed of hundreds of core elements that self-stand on the lower support plate, and core elements does not have support to constrain vertical displacement in order to avoid effects such as thermal elongation. When an earthquake occurs, the group vibration behavior including the rising of core elements in the vertical direction, the collision with adjacent core elements in the horizontal direction, and the fluid structure interaction is observed. The three dimensional core group vibration analysis code (REVIAN-3D) for evaluating these has been constructed. In this study, to grasp and estimate the group vibration behavior with and without a core former under the earthquake motion, seismic experiment of hexagonal multi bundle model using core element mock-up was conducted. These test results show that the presence of the core former decrease the horizontal displacements and increases core compaction. And the test results are used for the verification data of the analysis code REVIAN-3D.[1]

Fast Reactor Core Seismic Experiment and Analysis Under Strong Excitation

2018 ◽  
Author(s):  
Tomohiko Yamamoto ◽  
Akihisa Iwasaki ◽  
Kazuteru Kawamura ◽  
Shinichiro Matsubara ◽  
Hidenori Harada
Keyword(s):  
Fast Reactor ◽  
Structural Integrity ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Vertical Displacement ◽  
Three Dimensions ◽  
Analysis Model ◽  
Core Element ◽  
Seismic Experiment ◽  
Strong Excitation

In design of fast reactor (FR) core components, seismic response must be evaluated in order to ensure the structural integrity. Thus, a core seismic analysis method has been developed to evaluate 3D core vibration behavior considering fluid structure interaction and vertical displacement (upward). Thirty seven 1/1.5 scale core element models which shape hexagonal-arrangement were used to validate the core element vibration analysis code in three dimensions (REVIAN-3D). Based on the test data, the newly incorporated analysis model has been verified to respond to strong excitation.

Development of a Core Seismic Analysis Method for a Fast Reactor

2016 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Kazuo Hirota ◽  
Masatsugu Monde ◽  
Shinichiro Matsubara ◽  
Iwao Ikarimoto
Keyword(s):  
Fast Reactor ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Great Earthquake ◽  
Analysis Method ◽  
Core Element ◽  
The Core ◽  
Vibration Behavior ◽  
Core Elements ◽  
Core Seismic Analysis

A fast reactor core consists of several hundreds of core assemblies, which are hexagonal flexible beams embedded at the lower support plate in a hexagonal arrangement, separated by small gaps, and immersed in a fluid. Core assemblies have no support for vertical fixing in order to avoid the influence of thermal expansion and swelling. These days, in Japan, it has become necessary to postulate huge earthquakes in seismic evaluations. If a great earthquake occurs, the large displacement and impact force in each core assembly may cause problems with control rod insertability and core assembly strength. So, it is necessary to grasp the vibration behavior of the core elements during an earthquake in order to appropriately design the core support structures and core elements of a fast reactor. Thus, considering horizontal and vertical forces (impact forces and fluid forces) acting on the core elements during an earthquake, a core seismic analysis method has been developed to evaluate 3D core vibration behavior considering fluid structure interaction and vertical displacements (rising). This paper summarizes the details of the core element vibration analysis code in 3D (REVIAN-3D) that has been developed.

CFD Investigation of Thermal-Hydraulic Behaviors in Full Reactor Core for Sodium-Cooled Fast Reactor

2018 ◽  
Author(s):  
Jing Chen ◽  
Dalin Zhang ◽  
Suizheng Qiu ◽  
Kui Zhang ◽  
Mingjun Wang ◽  
...  
Keyword(s):  
Fast Reactor ◽  
Power Distribution ◽  
Three Dimensional ◽  
Reactor Core ◽  
Heat Removal ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Heat Removal System ◽  
China Experimental Fast Reactor ◽  
Full Core

As the first developmental step of the sodium-cooled fast reactor (SFR) in China, the pool-type China Experimental Fast Reactor (CEFR) is equipped with the openings and inter-wrapper space in the core, which act as an important part of the decay heat removal system. The accurate prediction of coolant flow in the reactor core calls for complete three-dimensional calculations. In the present study, an investigation of thermal-hydraulic behaviors in a 180° full core model similar to that of CEFR was carried out using commercial Computational Fluid Dynamics (CFD) software. The actual geometries of the peripheral core baffle, fluid channels and narrow inter-wrapper gap were built up, and numerous subassemblies (SAs) were modeled as the porous medium with appropriate resistance and radial power distribution. First, the three-dimensional flow and temperature distributions in the full core under normal operating condition are obtained and quantitatively analyzed. And then the effect of inter-wrapper flow (IWF) on heat transfer performance is evaluated. In addition, the detailed flow path and direction in local inter-wrapper space including the internal and outlet regions are captured. This work can provide some valuable understanding of the core thermal-hydraulic phenomena for the research and design of SFRs.

Core Seismic Experiment and Analysis of Hexagonal Bundle Model for Fast Reactor

2017 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Shinichiro Matsubara ◽  
Tomohiko Yamamoto ◽  
Seiji Kitamura ◽  
Shigeki Okamura
Keyword(s):  
Seismic Response ◽  
Fast Reactor ◽  
Impact Force ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Three Dimensions ◽  
Analysis Method ◽  
Core Element ◽  
Core Elements ◽  
Advanced Analysis

To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Therefore, advanced analysis method must be developed to calculate seismic response of a fast reactor core. The fast reactor core is generally made of several hundred core elements which are hexagonal flexible beams embedded at the lower support plate in hexagonal arrangement. When a big earthquake occurs, large horizontal displacement, vertical displacement (rising) and impact force of each core element may cause a trouble for control rod insertability and core element intensity. Therefore, a seismic analysis method of a fast reactor core considering three-dimensional nonlinear behavior, such as impact, fluid-structure interaction, was developed. 1/1.5 scale 37 core element mock-ups hexagonal-matrix experiment was performed to validate the core elements vibration analysis code in three dimensions (REVIAN-3D). Vertical behavior (rising displacement) and horizontal behavior (impact force) were good agreement with experiments by the validation of REVIAN-3D.

Core Seismic Experiment and Analysis of a Large Number of Element Models for Fast Reactor

2017 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Shinichiro Matsubara ◽  
Tomohiko Yamamoto ◽  
Seiji Kitamura ◽  
Shigeki Okamura
Keyword(s):  
Fast Reactor ◽  
Structural Integrity ◽  
Impact Force ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Three Dimensions ◽  
Core Element ◽  
Core Components

To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Generally, the fast reactor core is made of several hundred core elements in hexagonal arrangement. When a big earthquake occurs, large horizontal displacement, vertical displacement (rising) and impact force of each core element may cause a trouble for control rod insertability, reactivity insertion and core element intensity. Therefore, a seismic analysis method of a fast reactor core considering three-dimensional nonlinear behavior, such as bouncing, impact, fluid-structure interaction, etc. was developed. Validation of the core element vibration analysis code in three dimensions (REVIAN-3D) was conducted by 1/1.5 scale 32 core element mock-ups one-row test and 1/2.5 scale 313 core element mock-ups hexagonal-matrix test. In this verification, the applicability of the result obtained on a single model test or a small number of scale tests is verified when the number of core components increases. The vertical behavior (rising displacement) and horizontal behavior (Impact force, horizontal response) as a single core element of the analysis result agreed very well with the experiments.

Fast Reactor Core Seismic Analysis for Verification of Assessment Model of Control Rod

2018 ◽  
Author(s):  
Akihisa Iwasaki ◽  
Shinichiro Matsubara ◽  
Kazuteru Kawamura ◽  
Hidenori Harada ◽  
Tomohiko Yamamoto
Keyword(s):  
Fuel Assembly ◽  
Seismic Analysis ◽  
Reactor Core ◽  
Assessment Model ◽  
Guide Tube ◽  
Analysis Method ◽  
Control Rod ◽  
Support Plate ◽  
The Core ◽  
Core Elements

The control rod guide tube self-stands on the core support plate. The control rod is inserted in the control rod guide tube, and the control rod hangs from the upper structure of the reactor. At scrum in case of an earthquake, the control rod is detached and it sits on the seating structure in the control rod guide tube (Fig.1). In a vertical earthquake, the control rod guide tube is raised from the core support plate, and the control rod is also raised from the control rod guide tube. Therefore, drawing out may arise. During the earthquake after scrum, the rising behavior is different from the other core elements because the control rod and the control rod guide tube rise interfering each other. The control rod guide tube is raised more easily than the fuel assembly by the vertical differential pressure of the core during operation, because the control rod guide tube is lighter than the fuel assembly. Therefore, it is necessary to restrain the rising of the control rod guide tube. The sleeve dashpot structure, in which a sleeve is attached on the upper surface of the receptacle tube, is employed. Moreover, the control rod guide tube is equipped with the control rod dashpot in order to restrain the rising displacement of the control rod. This paper summarizes the analysis method of the rising behavior of the single control rod guide tube and the rising behavior of the control rod and the control guide tube after the control rod is inserted.

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