Title: Prompt-fission-neutron spectra in the ²³⁹Pu(n,f) reaction

Abstract

Prompt-fission-neutron spectra from ${}_{239}\mathrm{Pu}$ ( $\mathit{n},\mathit{f}$) were measured with respect to ${}_{252}\mathrm{Cf}$ spontaneous fission for incident neutron energies from 0.7 to $700\mathrm{MeV}$ at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center. A newly designed high-efficiency fission chamber was coupled to the highly segmented Chi-Nu neutron liquid scintillator array to detect neutrons emitted in fission events. The double time-of-flight technique was used to deduce the incident neutron energies from the spallation target and the outgoing-neutron energies from the fission chamber. Prompt-fission-neutron spectra (PFNS) were measured with respect to ${}_{252}\mathrm{Cf}$ spontaneous fission down to $200\mathrm{keV}$ and up to about $12\mathrm{MeV}$ for all the incident neutron energies with typical total uncertainties well below $2\%$ up to about 7-MeV outgoing-neutron energy. The general trend of PFNS is well reproduced by JEFF3.3 and ENDF evaluations, although a better agreement is found with JEFF3.3. Discrepancies were observed for the low-energy part of the spectra, especially around the opening of the second-, third- and fourth-chance fission. Additionally, neutron average kinetic energies as a function of incident neutron energy are obtained experimentally with reported total uncertainties below $0.5\%$. The measured values agree with the most recent data. The trend is fairly well reproduced by the JEFF3.3 evaluation, although it fails to reproduce the experimental values within their uncertainties.

Authors:

Marini, P.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9537-8126"

Taieb, J. ^[1]; Laurent, B.  ^[1];

• Search DOE PAGES for author "Laurent, B."
• Search DOE PAGES for ORCID "0000-0002-9255-8145"

Belier, G. ^[1]; Chatillon, A. ^[1]; Etasse, D. ^[2]; Morfouace, P. ^[1]; Devlin, M.  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-6948-2154"

Gomez, J. A.  ^[3];

• Search DOE PAGES for author "Gomez, J. A."
• Search DOE PAGES for ORCID "0000-0003-3958-9054"

Haight, R. C. ^[3]; Kelly, K. J.  ^[3];

• Search DOE PAGES for author "Kelly, K. J."
• Search DOE PAGES for ORCID "0000-0002-2845-9644"

O'Donnell, J. M. ^[3]; Schmitt, K. T. ^[3]

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+ Show Author Affiliations

1. Atomic Energy Commission (CEA), Arpajon (France)
2. Univ. de Caen (France)
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Publication Date:

Mon Apr 27 00:00:00 EDT 2020

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1726181

Report Number(s):

LA-UR-19-31206
Journal ID: ISSN 2469-9985; TRN: US2205076

Grant/Contract Number:  

89233218CNA000001; AC52-06NA25396

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review C

Additional Journal Information:

Journal Volume: 101; Journal Issue: 4; Journal ID: ISSN 2469-9985

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Fission; nucleon induced nuclear reactions