Investigation of Supercells for Preparation of Homogenized Cross Sections for Prismatic Deep Burn VHTR Calculations

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In Very High Temperature Reactors (VHTRs), the long mean-free-path and large migration area of neutrons leads to spectral influences between fuel and reflector zones over long distances. This presents significant challenges to the validity of the classic two-step approach of cross section preparation wherein infinite lattice transport calculations are performed on relatively small physical domains (e.g. single assembly) in order to compute homogenized few-group cross sections for whole core analysis. Effects of the inner and outer reflectors render infinite lattice calculations on a single peripheral fuel assembly quite inaccurate, while burnable poison locations affect neighboring assemblies as well. Use of ... continued below

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Pope, Michael A.; Ortensi, Javier & Ougouag, Abderafi October 1, 2010.

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In Very High Temperature Reactors (VHTRs), the long mean-free-path and large migration area of neutrons leads to spectral influences between fuel and reflector zones over long distances. This presents significant challenges to the validity of the classic two-step approach of cross section preparation wherein infinite lattice transport calculations are performed on relatively small physical domains (e.g. single assembly) in order to compute homogenized few-group cross sections for whole core analysis. Effects of the inner and outer reflectors render infinite lattice calculations on a single peripheral fuel assembly quite inaccurate, while burnable poison locations affect neighboring assemblies as well. Use of transuranics-only (TRU) Deep Burn fuel in a prismatic VHTR (DB-VHTR) presents the additional challenge of producing vastly different neutron spectra between fresh and burned fuel. ?This paper presents the progress in seeking a systematic method for generation of diffusion theory data in optically thin, multiply-heterogeneous reactors in a production context. A companion paper presents the underlying theory and systematic development of the methodology. In the context of this work, a supercell refers to an extended domain surrounding a region of interest. The extended domain is used to decouple the solution in this region of interest from the boundary conditions of the problem. This is an extension of the concept of color set, which was demonstrated to work very well for light water reactors (LWR). However, a half-assembly in an LWR presents a greater neutronic depth (in mean free paths) than in a VHTR. ??In order to make the supercell calculations more computationally manageable, an initial calculation is performed on a small domain and individual cells (individual compacts or coolant channels with graphite surrounding) are homogenized then used in the supercell calculations. This allows faster computation on the larger domain while retaining the overall hexagonal geometry of the fuel blocks. An application of this supercell concept using the DRAGON transport code is evaluated in this work for its effectiveness and practicality as part of an overall cross section preparation scheme for prismatic DB-VHTR reactors. The sizes of supercells for a peripheral fuel block are evaluated using independence from boundary conditions as an indicator.

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  • 5th International Topical Meeting on High Temperature Reactor Technology (HTR-2010),Prague, Czech Republic,10/18/2010,10/20/2010

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  • Report No.: INL/CON-10-18045
  • Grant Number: DE-AC07-05ID14517
  • Office of Scientific & Technical Information Report Number: 1016175
  • Archival Resource Key: ark:/67531/metadc833619

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  • October 1, 2010

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  • May 19, 2016, 3:16 p.m.

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  • June 20, 2016, 2 p.m.

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Pope, Michael A.; Ortensi, Javier & Ougouag, Abderafi. Investigation of Supercells for Preparation of Homogenized Cross Sections for Prismatic Deep Burn VHTR Calculations, article, October 1, 2010; Idaho Falls, Idaho. (digital.library.unt.edu/ark:/67531/metadc833619/: accessed December 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.