Uncertainty analysis for secondary energy distributions

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In many transport calculations the integral design parameter of interest (response) is determined mainly by secondary particles such as gamma rays from (n,..gamma..) reactions or secondary neutrons from inelastic scattering events or (n,2n) reactions. Standard sensitivity analysis usually allows to calculate the sensitivities to the production cross sections of such secondaries, but an extended formalism is needed to also obtain the sensitivities to the energy distribution of the generated secondary particles. For a 30-group standard cross-section set 84% of all non-zero table positions pertain to the description of secondary energy distributions (SED's) and only 16% to the actual reaction cross ... continued below

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Pages: 12

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Gerstl, S.A.W. January 1, 1978.

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In many transport calculations the integral design parameter of interest (response) is determined mainly by secondary particles such as gamma rays from (n,..gamma..) reactions or secondary neutrons from inelastic scattering events or (n,2n) reactions. Standard sensitivity analysis usually allows to calculate the sensitivities to the production cross sections of such secondaries, but an extended formalism is needed to also obtain the sensitivities to the energy distribution of the generated secondary particles. For a 30-group standard cross-section set 84% of all non-zero table positions pertain to the description of secondary energy distributions (SED's) and only 16% to the actual reaction cross sections. Therefore, any sensitivity/uncertainty analysis which does not consider the effects of SED's is incomplete and neglects most of the input data. This paper describes the methods of how sensitivity profiles for SED's are obtained and used to estimate the uncertainty of an integral response due to uncertainties in these SED's. The detailed theory is documented elsewhere and implemented in the LASL sensitivity code SENSIT. SED sensitivity profiles have proven particularly valuable in cross-section uncertainty analyses for fusion reactors. Even when the production cross sections for secondary neutrons were assumed to be without error, the uncertainties in the energy distribution of these secondaries produced appreciable uncertainties in the calculated tritium breeding rate. However, complete error files for SED's are presently nonexistent. Therefore, methods will be described that allow rough error estimates due to estimated SED uncertainties based on integral SED sensitivities.

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Pages: 12

Notes

Dep. NTIS, PC A02/MF A01.

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  • Workshop on theory and application of sensitivity and uncertainty analysis, Oak Ridge, TN, USA, 22 Aug 1978

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  • Report No.: LA-UR-78-2457
  • Report No.: CONF-780858-4
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 6441598
  • Archival Resource Key: ark:/67531/metadc1209662

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • January 1, 1978

Added to The UNT Digital Library

  • July 5, 2018, 11:11 p.m.

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  • Oct. 17, 2018, 1:51 p.m.

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Gerstl, S.A.W. Uncertainty analysis for secondary energy distributions, article, January 1, 1978; United States. (digital.library.unt.edu/ark:/67531/metadc1209662/: accessed December 11, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.