Seven surrogate precursors for modeling delayed neutron decay and predicting reactivity

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The use of a different set of group decay constants for each fissionable nuclide complicates analysis of the dynamic behavior of fast reactors. A fast reactor containing six principal fissioning nuclides of uranium and plutonium must, in effect, be described by 36 delayed neutron groups. Additionally, the use of group decay constants that depend on the neutron energy spectrum makes it difficult to select values that describe the dynamic response of epithermal systems because virtually all delayed neutron activity measurements have been performed for fast or thermal-neutron-induced fission. Clearly, it would be desirable to have a single set of group ... continued below

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6 p.

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Loaiza, D.J. & Haskin, F.E. December 31, 1997.

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The use of a different set of group decay constants for each fissionable nuclide complicates analysis of the dynamic behavior of fast reactors. A fast reactor containing six principal fissioning nuclides of uranium and plutonium must, in effect, be described by 36 delayed neutron groups. Additionally, the use of group decay constants that depend on the neutron energy spectrum makes it difficult to select values that describe the dynamic response of epithermal systems because virtually all delayed neutron activity measurements have been performed for fast or thermal-neutron-induced fission. Clearly, it would be desirable to have a single set of group decay constants that could be applied to all fissionable nuclides. A set of seven fixed decay constants is proposed herein. Each of the proposed decay constants is associated with a specific, dominant delayed neutron precursor. In effect, each group is represented by a single surrogate precursor. Using recently measured delayed neutron activities for U-235 and Np-237, the proposed set of decay constants actually improved the goodness of fit to the data. For other fissionable nuclides lacking experimental data, a method has been devised to obtain yields consistent with the proposed set of decay constants from the traditional six-group parameters. This transformation is accomplished without altering the traditional inferred reactivity scale.

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6 p.

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INIS; OSTI as DE98007150

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  • International conference on the physics of nuclear science and technology, Long Island, NY (United States), 5-8 Oct 1998

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  • Other: DE98007150
  • Report No.: LA-UR--97-5077
  • Report No.: CONF-981003--
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 674725
  • Archival Resource Key: ark:/67531/metadc708090

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  • December 31, 1997

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  • Sept. 12, 2015, 6:31 a.m.

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  • Feb. 29, 2016, 7:25 p.m.

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Loaiza, D.J. & Haskin, F.E. Seven surrogate precursors for modeling delayed neutron decay and predicting reactivity, article, December 31, 1997; New Mexico. (digital.library.unt.edu/ark:/67531/metadc708090/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.