Study on Temperature Distribution of Pebble-Bed HTR Fuel Element by Using Boundary Element Method

2013 ◽  
Author(s):  
Haitao Wang ◽  
Xin Wang
Keyword(s):  
Fuel Element ◽  
Boundary Element ◽  
Large Scale ◽  
Maximum Temperature ◽  
Element Formulation ◽  
Desktop Computer ◽  
Pebble Bed ◽  
Graphite Matrix ◽  
Fuel Particles ◽  
Fuel Elements

Spherical fuel elements with a diameter of 60mm are basic units of the nuclear fuel for the pebble-bed high temperature gas-cooled reactor (HTR). Each fuel element is treated as a graphite matrix containing around 10,000 randomly distributed fuel particles. The essential safety concept of the pebble-bed HTR is based on the objective that maximum temperature of the fuel particles does not exceed the design value. In this paper, a microstructure-based boundary element model is proposed for the large-scale thermal analysis of a spherical fuel element. This model presents detailed structural information of a large number of coated fuel particles dispersed in a spherical graphite matrix in order that temperature distributions at the level of fuel particles can be evaluated. The model is meshed with boundary elements in conjunction with the fast multipole method (FMM) in order that such large-scale computation is performed only in a personal desktop computer. Taking advantage of the fact that fuel particles are of the same shape, a similar sub-domain approach is used to establish the temperature translation mechanism between various layers of each fuel particle and to simplify the associated boundary element formulation. The numerical results demonstrate large-scale capacity of the proposed method for the multi-level temperature evaluation of the pebble-bed HTR fuel elements.

The Gasification of Graphite Matrix in Pebble Bed Reactors

2009 ◽  
Author(s):  
Xinli Yu ◽  
Suyuan Yu
Keyword(s):  
High Temperature ◽  
Corrosion Rate ◽  
Fuel Element ◽  
Pebble Bed ◽  
The Core ◽  
Graphite Matrix ◽  
Matrix Graphite ◽  
Element Matrix ◽  
Fuel Elements ◽  
High Temperature Gas

This paper mainly deals with the simulations of graphite matrix of the spherical fuel elements by steam in normal operating conditions. The fuel element matrix graphite was firstly simplified to an annular part in the simulations. Then the corrosions to the matrix graphite in 10 MW High Temperature Gas-cooled Reactor (HTR-10) and the High Temperature Gas-cooled Reactor—–Pebble-bed Module (HTR-PM) were investigated respectively. The results showed that the gasification of fuel element matrix graphite was uniform and mainly occurred at the bottom of the core in both of the reactors in the mean residence time of the spherical fuel elements. This was mainly caused by the designed high temperature at the bottom. The total mass gasified in HTR-PM was much greater than the HTR-10, while it did not mean much severer corrosion occurred there. As it is known the core volume of HTR-PM is much larger than the HTR-10, which will result in much greater consumed graphite even for the same corrosion rate. The steam only lost about 1 to 3 percent after flowing through the cores in both reactors for different steam conditions. The corrosion of graphite became worse when the steam concentrations increased in helium coolant. The results also indicated that the corrosion rate of fuel element matrix graphite tended to increase slightly with the prolonging of the service time.

scholarly journals The Electric Current Effect on Electrochemical Deconsolidation of Spherical Fuel Elements

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Xiaotong Chen ◽  
Zhenming Lu ◽  
Hongsheng Zhao ◽  
Bing Liu ◽  
Junguo Zhu ◽  
...  
Keyword(s):  
Electric Current ◽  
Photoelectron Spectroscopy ◽  
Energy Dispersive Spectrometer ◽  
Graphite Powder ◽  
X Ray ◽  
Graphite Matrix ◽  
Free Particles ◽  
The Matrix ◽  
Fuel Particles ◽  
Fuel Elements

For High-Temperature Gas-Cooled Reactor in China, fuel particles are bonded into spherical fuel elements by a carbonaceous matrix. For the study of fuel failure mechanism from individual fuel particles, an electrochemical deconsolidation apparatus was developed in this study to separate the particles from the carbonaceous matrix by disintegrating the matrix into fine graphite powder. The deconsolidated graphite powder and free particles were characterized by elemental analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and ceramography. The results showed that the morphology, size distribution, and element content of deconsolidated graphite matrix and free particles were notably affected by electric current intensity. The electrochemical deconsolidation mechanism of spherical fuel element was also discussed.

Two-Energy Modeling of Heat Conduction in a Heterogeneous Spherical Fuel Element

2009 ◽  
Author(s):  
Carlos V. Pessoa ◽  
Jian Su ◽  
Claudio L. de Oliveira
Keyword(s):  
Heat Conduction ◽  
Fuel Element ◽  
Integral Transform ◽  
Equation Model ◽  
Fast Evaluation ◽  
Graphite Matrix ◽  
Hybrid Solution ◽  
The Matrix ◽  
Steady State Heat ◽  
Fuel Particles

In this work, heat conduction in a typical spherical fuel element (pebble) of a pebble-bed high temperature reactor was studied. The fuel element is composed by a particulate region with spherical inclusions, the UO2 fuel particles (TRISO), dispersed in a graphite matrix. The two energy equation model was applied to the particulate region, generating two macroscopic temperatures, respectively, of the fuel and of the matrix. Analytical solutions are obtained for steady-state heat conduction. Transient analysis was carried out by using the generalized integral transform technique (GITT), which requires low computational efforts and allows a fast evaluation of the two macroscopic transient temperatures of the particulate region. The solution by GITT leads to a system of ordinary differential equations with the unknown transformed potentials, which is solved numerically to obtain the hybrid solution of the original partial differential equation. Numerical results for several testing cases are presented.

Numerical Analysis of the Residual Heat Removal for the Spent Fuel Canister of HTR-PM in Fuel Loading Process

2014 ◽  
Author(s):  
Jinhua Wang ◽  
Bing Wang ◽  
Bin Wu
Keyword(s):  
High Temperature ◽  
Natural Ventilation ◽  
Maximum Temperature ◽  
Spent Fuel ◽  
Fuel Loading ◽  
Pebble Bed ◽  
Loading Process ◽  
Accident Conditions ◽  
Fuel Elements ◽  
Residual Heat

High Temperature Gas Cooled Reactor (HTGR) has inherent safety, and has been selected as one of the candidates for the Gen-IV nuclear energy system. In china, the project of the High Temperature Reactor Pebble bed Module (HTR-PM) is in design and construction process. Spherical fuel elements are chosen for the HTR-PM and the spent fuel elements will be stored in canister. The spent fuel canister will be delivered to wells for storage when fully loaded. The canister is covered by a steel cask for radiation shielding, and the cask is covered by a boron polyethylene sleeve to absorb neutrons from decay in fuel loading process. Normally, the residual heat is discharged by forced ventilation in fuel loading process. An auxiliary fan is set on top of the cask considering the possible mechanical failure for the operating fan. When losing normal power supply, the emergency power will be provided to the fans by the two line diesel generators respectively. In extreme conditions of mechanical failure for both fans, the residual heat could be discharged by natural ventilation. The temperature profiles of the different structures were studied in this paper with CFD method for both normal and accident conditions. The calculation results showed that, the maximum temperature of all of the structures are lower than the safety temperature limits in either normal or accident conditions; the temperature decreases rapidly with radial distance in the canister, and the maximum temperature is located at the center of the fuel pebble bed. So it is feasible to remove the residual heat of the spent fuel by natural ventilation in accident condition, and in the natural ventilation condition, the maximum temperature of the spent fuel, the canister shell, the shielding cask, and the boron polyethylene sleeve are lower than their safety temperature limits.

Filtration Technology Research of Graphite Dust Produced in Spent Fuel Transportation Process in HTR-PM

2018 ◽  
Author(s):  
Jinhua Wang ◽  
Bing Wang ◽  
Bin Wu ◽  
Yue Li ◽  
Haitao Wang
Keyword(s):  
High Temperature ◽  
Fuel Element ◽  
Nuclear Power ◽  
Storage System ◽  
Spent Fuel ◽  
Graphite Matrix ◽  
Fuel Storage ◽  
Fuel Elements ◽  
And Storage ◽  
High Temperature Gas

With the continuous development of the nuclear power technology in the world, all countries in the world are becoming more and more interested in the inherent safety of nuclear power technology, while the research and development of the spherical bed type high temperature gas cooled reactor nuclear power technology in China has formally catered to this demand. As a major national science and technology project, since the construction of the high temperature gas cooled reactor demonstration project (HTR-PM) since 2012, the civil construction of the nuclear island has been basically completed, the installation of equipment has been carried out orderly, and many process systems have entered debugging and operation stage gradually. As an important auxiliary process system, fuel handling and storage system for online refueling of the pebble bed high temperature gas cooled reactor, plays an important role in relation to the stable operation of the reactor. The main functions of the fuel handling and storage system are loading the fresh fuel elements and unloading the spent fuel elements which has reached its target burnup continuously for reactor operation, the spent fuel elements would be discharged into the spent fuel canister firstly, when the spent fuel storage canister is full of spent fuel, the canister would be sealed through welding method, and then the spent fuel canister would be transferred and stored in the spent fuel storage silo with the ground crane system. The fuel element of the pebble bed high temperature gas cooled reactor is spherical fuel element with graphite matrix, the fuel elements will have friction and collision with the inner wall of the pipeline in transporting process, which will produce graphite dust, the graphite dust should be removed continuously though filtration method, so as not to affect the fuel elements transportation in pipeline. This article focus on the production mechanism and filtering method of the graphite dust in graphite matrix fuel element transporting process in pipeline, to study the graphite dust removal technology, and then we could provide theoretical guidance for the design and operation of the key system and equipment for HTR-PM.

Burnup characteristic of CERMET and TRISO fuel particles used in Boiling Water Reactor with Pebble-Bed Coated Particles

2014 ◽  
Vol 2014 (1) ◽  
pp. 17-22
Author(s):  
Abdelfettah Benchrif ◽  
◽  
Abdelouahed Chetaine ◽  
Hamid Amsil ◽  
◽  
...  
Keyword(s):  
Boiling Water ◽  
Boiling Water Reactor ◽  
Pebble Bed ◽  
Water Reactor ◽  
Coated Particles ◽  
Triso Fuel ◽  
Fuel Particles

A hybrid virtual–boundary element formulation for heterogeneous materials

2021 ◽  
pp. 106404
Author(s):  
Marco Lo Cascio ◽  
Alberto Milazzo ◽  
Ivano Benedetti
Keyword(s):  
Boundary Element ◽  
Heterogeneous Materials ◽  
Element Formulation ◽  
Virtual Boundary ◽  
Virtual Boundary Element

Reduced-Order Modeling of Unsteady Flows About Complex Configurations Using the Boundary Element Method

2002 ◽  
Vol 124 (4) ◽  
pp. 988-993 ◽  
Author(s):  
V. Esfahanian ◽  
M. Behbahani-nejad
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Three Dimensional ◽  
Unsteady Flows ◽  
Reduced Order Modeling ◽  
Element Formulation ◽  
Reduced Order Models ◽  
Reduced Order ◽  
Naca 0012 ◽  
Element Method

An approach to developing a general technique for constructing reduced-order models of unsteady flows about three-dimensional complex geometries is presented. The boundary element method along with the potential flow is used to analyze unsteady flows over two-dimensional airfoils, three-dimensional wings, and wing-body configurations. Eigenanalysis of unsteady flows over a NACA 0012 airfoil, a three-dimensional wing with the NACA 0012 section and a wing-body configuration is performed in time domain based on the unsteady boundary element formulation. Reduced-order models are constructed with and without the static correction. The numerical results demonstrate the accuracy and efficiency of the present method in reduced-order modeling of unsteady flows over complex configurations.

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