Asymptotic, multigroup flux reconstruction and consistent discontinuity factors

Trahan, Travis J.; Larsen, Edward W.

doi:10.1080/00223131.2015.1041568

Title: Asymptotic, multigroup flux reconstruction and consistent discontinuity factors

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Abstract

Recent theoretical work has led to an asymptotically derived expression for reconstructing the neutron flux from lattice functions and multigroup diffusion solutions. The leading-order asymptotic term is the standard expression for flux reconstruction, i.e., it is the product of a shape function, obtained through a lattice calculation, and the multigroup diffusion solution. The first-order asymptotic correction term is significant only where the gradient of the diffusion solution is not small. Inclusion of this first-order correction term can significantly improve the accuracy of the reconstructed flux. One may define discontinuity factors (DFs) to make certain angular moments of the reconstructed flux continuous across interfaces between assemblies in 1-D. Indeed, the standard assembly discontinuity factors make the zeroth moment (scalar flux) of the reconstructed flux continuous. The inclusion of the correction term in the flux reconstruction provides an additional degree of freedom that can be used to make two angular moments of the reconstructed flux continuous across interfaces by using current DFs in addition to flux DFs. Thus, numerical results demonstrate that using flux and current DFs together can be more accurate than using only flux DFs, and that making the second angular moment continuous can be more accurate than making themore » zeroth moment continuous.« less

Authors:

Trahan, Travis J. ^[1]; Larsen, Edward W. ^[2]

Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Michigan, Ann Arbor, MI (United States)
Univ. of Michigan, Ann Arbor, MI (United States)

Publication Date:: Tue May 12 00:00:00 EDT 2015

Research Org.:: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1227733

Report Number(s):: LA-UR-15-20351
Journal ID: ISSN 0022-3131; TRN: US1600444

Grant/Contract Number:: AC52-06NA25396

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Nuclear Science and Technology (Tokyo)

Additional Journal Information:: Journal Name: Journal of Nuclear Science and Technology (Tokyo); Journal Volume: 52; Journal Issue: 7-8; Journal ID: ISSN 0022-3131

Country of Publication:: United States

Language:: English

Subject:: 22 GENERAL STUDIES OF NUCLEAR REACTORS; flux reconstruction; discontinuity factors; asymptotic analysis; neutron diffusion equation; reactor physics; numerical simulation

Citation Formats


                    Trahan, Travis J., and Larsen, Edward W. Asymptotic, multigroup flux reconstruction and consistent discontinuity factors.  United States: N. p., 2015. 
Web.  doi:10.1080/00223131.2015.1041568.

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                    Trahan, Travis J., & Larsen, Edward W. Asymptotic, multigroup flux reconstruction and consistent discontinuity factors.  United States.  https://doi.org/10.1080/00223131.2015.1041568

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                    Trahan, Travis J., and Larsen, Edward W. Tue .  
"Asymptotic, multigroup flux reconstruction and consistent discontinuity factors".  United States.  https://doi.org/10.1080/00223131.2015.1041568.  https://www.osti.gov/servlets/purl/1227733.

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@article{osti_1227733,

  title        = {Asymptotic, multigroup flux reconstruction and consistent discontinuity factors},

  author       = {Trahan, Travis J. and Larsen, Edward W.},

  abstractNote = {Recent theoretical work has led to an asymptotically derived expression for reconstructing the neutron flux from lattice functions and multigroup diffusion solutions. The leading-order asymptotic term is the standard expression for flux reconstruction, i.e., it is the product of a shape function, obtained through a lattice calculation, and the multigroup diffusion solution. The first-order asymptotic correction term is significant only where the gradient of the diffusion solution is not small. Inclusion of this first-order correction term can significantly improve the accuracy of the reconstructed flux. One may define discontinuity factors (DFs) to make certain angular moments of the reconstructed flux continuous across interfaces between assemblies in 1-D. Indeed, the standard assembly discontinuity factors make the zeroth moment (scalar flux) of the reconstructed flux continuous. The inclusion of the correction term in the flux reconstruction provides an additional degree of freedom that can be used to make two angular moments of the reconstructed flux continuous across interfaces by using current DFs in addition to flux DFs. Thus, numerical results demonstrate that using flux and current DFs together can be more accurate than using only flux DFs, and that making the second angular moment continuous can be more accurate than making the zeroth moment continuous.},

  doi          = {10.1080/00223131.2015.1041568},

  journal      = {Journal of Nuclear Science and Technology (Tokyo)},

  number       = 7-8,

  volume       = 52,

  place        = {United States},

  year         = {Tue May 12 00:00:00 EDT 2015},

  month        = {Tue May 12 00:00:00 EDT 2015}

}

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