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Title: Preliminary Evaluation and Uncertainty Quantification of the Prompt Fission Neutron Spectrum of {sup 239}Pu

Abstract

Low evaluated uncertainties were obtained in a previous evaluation of the {sup 239}Pu prompt fission neutron spectrum and associated covariances for incident neutrons of 0.5 MeV, which were enlarged a-posteriori before being incorporated into ENDF/B-VII.1. These low evaluated uncertainties triggered an in-depth study and improved estimate of experimental as well as model uncertainties. Here, we will summarize these efforts and show that the improved estimate of experimental and model uncertainties leads to corresponding evaluated uncertainties in good agreement with uncertainties obtained in a statistical analysis based primarily on experimental information.

Authors:
 [1];  [1]; ;  [2];  [1];  [2];  [3];  [4]; ;  [5]
  1. T-2: Nuclear and Particle Physics, Astrophysics and Cosmology, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
  2. LANSCE-NS: Neutron and Nuclear Science, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
  3. Nuclear Engineering Division, Argonne National Laboratory, Coronado, CA 92118 (United States)
  4. Nuclear Data Section, International Atomic Energy Agency, Vienna, A-1400 (Austria)
  5. X-Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
Publication Date:
OSTI Identifier:
22436774
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Data Sheets; Journal Volume: 123; Conference: International workshop on nuclear data covariances, Santa Fe, NM (United States), 28 Apr - 1 May 2014; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; DATA COVARIANCES; EVALUATION; FISSION NEUTRONS; KEV RANGE 100-1000; NUCLEAR DATA COLLECTIONS; PLUTONIUM 239

Citation Formats

Neudecker, D., E-mail: dneudecker@lanl.gov, Talou, P., Taddeucci, T.N., Haight, R.C., Kawano, T., Lee, H.Y., Smith, D.L., Capote, R., Rising, M.E., and White, M.C. Preliminary Evaluation and Uncertainty Quantification of the Prompt Fission Neutron Spectrum of {sup 239}Pu. United States: N. p., 2015. Web. doi:10.1016/J.NDS.2014.12.026.
Neudecker, D., E-mail: dneudecker@lanl.gov, Talou, P., Taddeucci, T.N., Haight, R.C., Kawano, T., Lee, H.Y., Smith, D.L., Capote, R., Rising, M.E., & White, M.C. Preliminary Evaluation and Uncertainty Quantification of the Prompt Fission Neutron Spectrum of {sup 239}Pu. United States. doi:10.1016/J.NDS.2014.12.026.
Neudecker, D., E-mail: dneudecker@lanl.gov, Talou, P., Taddeucci, T.N., Haight, R.C., Kawano, T., Lee, H.Y., Smith, D.L., Capote, R., Rising, M.E., and White, M.C. Thu . "Preliminary Evaluation and Uncertainty Quantification of the Prompt Fission Neutron Spectrum of {sup 239}Pu". United States. doi:10.1016/J.NDS.2014.12.026.
@article{osti_22436774,
title = {Preliminary Evaluation and Uncertainty Quantification of the Prompt Fission Neutron Spectrum of {sup 239}Pu},
author = {Neudecker, D., E-mail: dneudecker@lanl.gov and Talou, P. and Taddeucci, T.N. and Haight, R.C. and Kawano, T. and Lee, H.Y. and Smith, D.L. and Capote, R. and Rising, M.E. and White, M.C.},
abstractNote = {Low evaluated uncertainties were obtained in a previous evaluation of the {sup 239}Pu prompt fission neutron spectrum and associated covariances for incident neutrons of 0.5 MeV, which were enlarged a-posteriori before being incorporated into ENDF/B-VII.1. These low evaluated uncertainties triggered an in-depth study and improved estimate of experimental as well as model uncertainties. Here, we will summarize these efforts and show that the improved estimate of experimental and model uncertainties leads to corresponding evaluated uncertainties in good agreement with uncertainties obtained in a statistical analysis based primarily on experimental information.},
doi = {10.1016/J.NDS.2014.12.026},
journal = {Nuclear Data Sheets},
number = ,
volume = 123,
place = {United States},
year = {Thu Jan 15 00:00:00 EST 2015},
month = {Thu Jan 15 00:00:00 EST 2015}
}
  • Low evaluated uncertainties were obtained in a previous evaluation of the 239Pu prompt fission neutron spectrum and associated covariances for incident neutrons of 0.5 MeV, which were enlarged a-posteriori before being incorporated into ENDF/B-VII.1. These low evaluated uncertainties triggered an in-depth study and improved estimate of experimental as well as model uncertainties. Here, we will summarize these efforts and show that the improved estimate of experimental and model uncertainties leads to corresponding evaluated uncertainties in good agreement with uncertainties obtained in a statistical analysis based primarily on experimental information.
  • Cited by 36
  • We present evaluations of the prompt fission neutron spectrum (PFNS) of (PU)-P-239 induced by 500 keV neutrons, and associated covariances. In a previous evaluation by Talon et al. (2010), surprisingly low evaluated uncertainties were obtained, partly due to simplifying assumptions in the quantification of uncertainties from experiment and model. Therefore, special emphasis is placed here on a thorough uncertainty quantification of experimental data and of the Los Alamos model predicted values entering the evaluation. In addition, the Los Alamos model was extended and an evaluation technique was employed that takes into account the qualitative differences between normalized model predicted valuesmore » and experimental shape data These improvements lead to changes in the evaluated PENS and overall larger evaluated uncertainties than in the previous work. However, these evaluated uncertainties are still smaller than those obtained in a statistical analysis using experimental information only, due to strong model correlations. Hence, suggestions to estimate model defect uncertainties are presented. which lead to more reasonable evaluated uncertainties. The calculated k(eff) of selected criticality benchmarks obtained with these new evaluations agree with each other within their uncertainties despite the different approaches to estimate model defect uncertainties. The k(eff) one standard deviations overlap with some of those obtained using ENDF/B-VILl, albeit their mean values are further away from unity. Spectral indexes for the Jezebel critical assembly calculated with the newly evaluated PFNS agree with the experimental data for selected (n,) and (n,f) reactions, and show improvements for highenergy threshold (n,2n) reactions compared to ENDF/B-VII.l. (C) 2015 Elsevier B.V. All rights reserved.« less
  • Cited by 4