Properties and microstructures of a matrix graphite for fuel elements of pebble-bed reactors after hightemperature purification at different temperatures

The gas-cooled reactor design with spherical fuel elements, referred to as high-temperature gas-cooled reactors (HTGR or HTR reactors) or pebble bed reactors has been already suggested by Farrington Daniels in the late 1940s; also referred to as Daniels’ pile reactor design. Under Rudolf Schulten the first pebble bed reactor, the 46MWth AVR Juelich reactor (Atom Versuchs-Reactor Jülich) was built in the late 1960s. It was in operation for 22 years and extensive testing confirmed its inherent safety.

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The Gasification of Graphite Matrix in Pebble Bed Reactors

Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications ◽

10.1115/icone17-75827 ◽

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.

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Modeling Packing of Spherical Fuel Elements in Pebble Bed Reactors Using DEM

Special Publication - Discrete Element Modelling of Particulate Media ◽

10.1039/9781849735032-00175 ◽

2012 ◽

pp. 175-183 ◽

Cited By ~ 1

Author(s):

H. Suikkanen ◽

J. Ritvanen ◽

P. Jalali ◽

R. Kyrki-Rajamäki

Keyword(s):

Pebble Bed ◽

Pebble Bed Reactors ◽

Fuel Elements

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

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2013-97454 ◽

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.

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