An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations
© 2017 When collapsing multi-group cross sections, a flux separability approximation is often used. This assumes the angular variation of the flux is independent of the energy dependence, which avoids angular dependence of the total multi-group cross section. This paper investigates the impact of th...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Elsevier BV
2021
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| Online Access: | https://hdl.handle.net/1721.1/134682 |
| _version_ | 1811098032892018688 |
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| author | Boyd, William Gibson, Nathan Forget, Benoit Smith, Kord |
| author2 | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Boyd, William Gibson, Nathan Forget, Benoit Smith, Kord |
| author_sort | Boyd, William |
| collection | MIT |
| description | © 2017 When collapsing multi-group cross sections, a flux separability approximation is often used. This assumes the angular variation of the flux is independent of the energy dependence, which avoids angular dependence of the total multi-group cross section. This paper investigates the impact of this approximation on fine-mesh deterministic multi-group transport methods for two PWR pin-cell benchmarks, which demonstrate errors of more than 1% in energy groups with large U-238 capture resonances and an eigenvalue bias of approximately 200 pcm between continuous energy Monte Carlo and deterministic transport methods, even when the “true” scalar flux is used to collapse cross sections. This paper also investigates two means of resolving this issue, but both are seen to have significant short-comings. First, the most direct and mathematically consistent approach is to use angularly-dependent multi-group cross sections. These cannot be easily computed for arbitrary geometries using traditional multi-group cross section generation methods, are not supported by most standard transport codes, and require significant spatial discretization. Second, SuPerHomogéneísation (SPH) factors are used to preserve reaction rates between continuous energy Monte Carlo and deterministic transport methods, but the SPH scheme requires knowledge of the reference source distribution, is dependent on the spatial discretization mesh, and is indiscriminate between various sources of approximation error. |
| first_indexed | 2024-09-23T17:08:53Z |
| format | Article |
| id | mit-1721.1/134682 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T17:08:53Z |
| publishDate | 2021 |
| publisher | Elsevier BV |
| record_format | dspace |
| spelling | mit-1721.1/1346822023-03-24T19:47:55Z An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations Boyd, William Gibson, Nathan Forget, Benoit Smith, Kord Massachusetts Institute of Technology. Department of Nuclear Science and Engineering © 2017 When collapsing multi-group cross sections, a flux separability approximation is often used. This assumes the angular variation of the flux is independent of the energy dependence, which avoids angular dependence of the total multi-group cross section. This paper investigates the impact of this approximation on fine-mesh deterministic multi-group transport methods for two PWR pin-cell benchmarks, which demonstrate errors of more than 1% in energy groups with large U-238 capture resonances and an eigenvalue bias of approximately 200 pcm between continuous energy Monte Carlo and deterministic transport methods, even when the “true” scalar flux is used to collapse cross sections. This paper also investigates two means of resolving this issue, but both are seen to have significant short-comings. First, the most direct and mathematically consistent approach is to use angularly-dependent multi-group cross sections. These cannot be easily computed for arbitrary geometries using traditional multi-group cross section generation methods, are not supported by most standard transport codes, and require significant spatial discretization. Second, SuPerHomogéneísation (SPH) factors are used to preserve reaction rates between continuous energy Monte Carlo and deterministic transport methods, but the SPH scheme requires knowledge of the reference source distribution, is dependent on the spatial discretization mesh, and is indiscriminate between various sources of approximation error. 2021-10-27T20:06:10Z 2021-10-27T20:06:10Z 2018 2019-09-26T13:45:24Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/134682 en 10.1016/J.ANUCENE.2017.09.052 Annals of Nuclear Energy Creative Commons Attribution-NonCommercial-NoDerivs License http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf Elsevier BV Prof. Forget via Chris Sherratt |
| spellingShingle | Boyd, William Gibson, Nathan Forget, Benoit Smith, Kord An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations |
| title | An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations |
| title_full | An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations |
| title_fullStr | An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations |
| title_full_unstemmed | An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations |
| title_short | An analysis of condensation errors in multi-group cross section generation for fine-mesh neutron transport calculations |
| title_sort | analysis of condensation errors in multi group cross section generation for fine mesh neutron transport calculations |
| url | https://hdl.handle.net/1721.1/134682 |
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