Numerical investigation of a heat transfer within the prismatic fuel assembly of a very high temperature reactor

Tak, Nam-il; Kim, Min-Hwan; Lee, Won Jae

doi:10.1016/j.anucene.2008.04.005

Cited by 54 publications

(19 citation statements)

References 4 publications

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“…More sophisticated thermal fluid codes must model the radial and axial flow in the gaps between the blocks to get a firmer picture of the temperature distribution within the fuel and core. Such analyses have only recently been attempted with CFD codes (Sato 2010, Tak 2008 but they indicate that the presence of bypass flow can increase the temperature of the coolant leaving a block by as much as 60°C. The increase in the maximum fuel temperature can be as high as 80°C.…”

Section: Prismatic Htgrmentioning

confidence: 99%

Next Generation Nuclear Plant Methods Technical Program Plan

Schultz¹,

Ougouag²,

Nigg³

et al. 2010

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Section: Prismatic Htgrmentioning

confidence: 99%

Next Generation Nuclear Plant Methods Technical Program Plan

Schultz¹,

Ougouag²,

Nigg³

et al. 2010

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“…Tak et al [2] report flow and temperature distributions from CFD calculations for a prismatic core with a nominal 1000°C outlet coolant temperature. However, they used a separate 1D code to provide flow rate information for their CFD calculations.…”

Section: Fig 2 Plan View Of the Prismatic Core Barrelmentioning

confidence: 99%

Effects of graphite surface roughness on bypass flow computations for an HTGR

Tung

Johnson

Satō

2012

Nuclear Engineering and Design

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Bypass flow in a prismatic high temperature gas reactor (HTGR) occurs between graphite blocks as they sit side by side in the core. Bypass flow is not intentionally designed to occur in the reactor, but is present because of tolerances in manufacture, imperfect installation and expansion and shrinkage of the blocks from heating and irradiation. It is desired to increase the knowledge of the effects of such flow; it has been suggested that it may be 20% of the total helium coolant flow [INL report 2007, INL/EXT-07-13289]. Computational fluid dynamic (CFD) simulations can provide estimates of the scale and impacts of bypass flow. Previous CFD calculations have examined the effects of bypass gap width, level and distribution of heat generation and effects of shrinkage. The present contribution examines the effects of graphite surface roughness on the bypass flow for different relative roughness factors on three gap widths. Such calculations should be validated using specific bypass flow measurements. While such experiments are currently underway for the specific reference prismatic HTGR design for the next generation nuclear plant (NGNP) program of the U.S. Dept. of Energy, the data are not yet available. To enhance confidence in the present calculations, wall shear stress and heat transfer results for several turbulence models and their associated wall treatments are first compared for flow in a single tube that is representative of a coolant channel in the prismatic HTGR core. The results are compared to published correlations for wall shear stress and Nusselt number in turbulent pipe flow. Turbulence models that perform well are then used to make bypass flow calculations in a symmetric one-twelfth sector of a prismatic block that includes bypass flow. The comparison of shear stress and Nusselt number results with published correlations constitutes a partial validation of the CFD model. Calculations are also compared to ones made previously using a different CFD code. Results indicate that increasing surface roughness increases the maximum fuel and helium temperatures as do increases in gap width. However, maximum coolant temperature variation due to increased gap width is not changed by surface roughness. INTRODUCTIONThe core of the reference prismatic version of the HTGR consists of stacks of hexagonal blocks of graphite drilled to accept cylindrical fuel compacts and to provide for coolant flow. Figure 1 illustrates the cross section of one such block. The smaller blue circles represent fuel elements while the red circles represent coolant channels. Gaps occur between adjacent hexagonal blocks where the coolant can flow, bypassing the coolant channels. Figure 1 also illustrates the location of a one-twelfth sector that is symmetric along each edge, one of which is a bypass flow gap. The CFD model used in the present calculations is based on the symmetric onetwelfth sector, which is extruded through the entire core.

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“…A three dimensional simulation using commercial CFD code CFX 11 was performed by N. Tak (Tak, N.I., Kim, M.-H., et al 2008). A simple unit cell model which was a one-twelfth sector of a typical fuel blocks were applied to evaluate the temperature distribution within the fuel blocks.…”

Section: Previous Work Reviewmentioning

confidence: 99%

“…Fig. 2 Core Arrangement of GT-MHR (Tak, N.I., Kim, M.-H., et al, 2008) The fuel used for the VHTR is called TRISO fuel which has fuel kernel in the center of the sphere and several layers surrounding the kernel to keep the fission gases inside the fuel and also to increase the structural strength. The TRISO fuel is mixed with graphite to form the fuel compact which will be inserted into the fuel holes to form the fuel block.…”

Section: Very High Temperature Gas-cooled Reactor (Vhtr)mentioning

confidence: 99%

Investigation on the Core Bypass Flow in a Very High Temperature Reactor

Hassan¹

2013

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Numerical investigation of a heat transfer within the prismatic fuel assembly of a very high temperature reactor

Cited by 54 publications

References 4 publications

Next Generation Nuclear Plant Methods Technical Program Plan

Next Generation Nuclear Plant Methods Technical Program Plan

Effects of graphite surface roughness on bypass flow computations for an HTGR

Investigation on the Core Bypass Flow in a Very High Temperature Reactor

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