Evaluation of the Fission and Capture Cross Sections of 24°Pu ; and 241Pu for ENDF
Evaluation of the Fission and Capture Cross Sections of 24°Pu ; and 241Pu for ENDF

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Published: 1979

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Since there were appreciable new data which were not available for ENDF/B-IV, new evaluations for 24°Pu and 241Pu were carried out for ENDF/B-V. The evaluation of the fission and capture cross sections is reviewed and problem areas are discussed. The neutron energy range of concern was from 10−5 eV to 20 MeV. Significant changes were made over the entire neutron energy region because of the new experimental data available. The problems in the evaluations due to discrepancies in the nuclear data are emphasized, particularly the 1-eV resonance in 24°Pu and the 0.3-eV resonance in 241Pu. The evaluation of the fission and capture cross sections for ENDF/B-V represents an improvement over the previous evaluation; however, there continues to be a need for accurate experimental data. 7 figures.

Evaluation of the Fission and Capture Cross Sections of [sup]240[/sup]Pu; and [sup]241[/sup]Pu for ENDF/B-V. [10/sup -5/ EV to 20 MeV].
Evaluation of the Fission and Capture Cross Sections of [sup]240[/sup]Pu; and [sup]241[/sup]Pu for ENDF/B-V. [10/sup -5/ EV to 20 MeV].

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Published: 1979

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Since there were appreciable new data which were not available for ENDF/B-IV, new evaluations for /sup 240/Pu and /sup 241/Pu were carried out for ENDF/B-V. The evaluation of the fission and capture cross sections is reviewed and problem areas are discussed. The neutron energy range of concern was from 10/sup -5/ eV to 20 MeV. Significant changes were made over the entire neutron energy region because of the new experimental data available. The problems in the evaluations due to discrepancies in the nuclear data are emphasized, particularly the 1-eV resonance in /sup 240/Pu and the 0.3-eV resonance in /sup 241/Pu. The evaluation of the fission and capture cross sections for ENDF/B-V represents an improvement over the previous evaluation; however, there continues to be a need for accurate experimental data. 7 figures.

Evaluation for ENDF
Evaluation for ENDF

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Published: 1976

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Capture and fission cross sections for 235U in the ''unresolved resonance'' energy region were evaluated to permit determination of local-average resonance parameters for the ENDF/B-IV cross section file. Microscopic data were examined for infinitely dilute average fission and capture cross sections and also for intermediate structure unlikely to be reproduced by statistical fluctuations of resonance widths and spacings within known laws. Evaluated cross sections, averaged over lethargy intervals greater than 0.1, were obtained as an average over selected data sets after appropriate renormalization. Estimated uncertainties are given for these evaluated average cross sections. The ''intermediate'' structure fluctuations common to a few independent data sets were approximated by straight lines joining successive cross sections at 120 selected energy points; the cross sections at the vertices were adjusted to reproduce the evaluated average cross sections over the broad energy regions. Data sources and methods are reviewed, output values are tabulated, and some modified procedures are suggested for future evaluations. Evaluated fission and capture integrals for the resolved resonance region are also tabulated. These are not in agreement with integrals based on the resonance parameters of ENDF/B versions III and IV. 8 tables, 5 figures.