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Title: Experimental spectrum averaged cross sections (SACS) in 252Cf(sf) neutron field and its impact on the evaluation of neutron standards

Journal Article · · EPJ Web of Conferences (Online)
 [1];  [1];  [2];  [1];  [3]; ORCiD logo [4]
  1. International Atomic Energy Agency (IAEA), Vienna (Austria)
  2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  3. Alternative Energies and Atomic Energy Commission (CEA), Cadarache (France)
  4. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
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A new evaluation of spectrum averaged cross sections (SACS) of 235U, 238U, and 239Pu measured in the 252Cf(sf) reference neutron field is presented and found to be consistent with the original Mannhart SACS evaluation in IRDF-2002. The comprehensive vetted experimental database that includes SACS ratio and absolute SACS measurements of major actinides is being used to update the SACS database employed as input of the new GMApy code to derive the Neutron Standards. An update of the current neutron standards based on Time Projection Chamber (TPC) shape data, a new comprehensive uncertainty quantification, and revised SACS experimental database is proposed which result in a 0.7% increase of the evaluated 239Pu(n,f)/235U(n,f) crosssection ratio in the 1–5 MeV energy region. The increase is due to a 0.3% reduction of the standard 235U(n,f) cross section and a 0.4% increase of the 239Pu(n,f) reference cross section in the 1–5 MeV energy region. Those changes are well within estimated USU fission cross-section uncertainties of 1.2%, but are relevant for the evaluated mean values.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89233218CNA000001
OSTI ID:
1975054
Report Number(s):
LA-UR-23-21724; TRN: US2314045
Journal Information:
EPJ Web of Conferences (Online), Vol. 281; ISSN 2100-014X
Publisher:
EDP SciencesCopyright Statement
Country of Publication:
United States
Language:
English

References (12)

Evaluation of the Neutron Data Standards journal February 2018
ENDF/B-VIII.0: The 8 th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data journal February 2018
Measurement of the 239Pu(n,f)/235U(n,f) Cross-Section Ratio with the NIFFTE fission Time Projection Chamber journal December 2021
Template for estimating uncertainties of measured neutron-induced fission cross-sections journal January 2018
IRDFF-II: A New Neutron Metrology Library journal January 2020
EXFOR-based simultaneous evaluation of neutron-induced uranium and plutonium fission cross sections for JENDL-5 journal April 2022
Fission cross-sections of 235U and 239Pu averaged over 252Cf neutron spectrum journal January 1978
Nuclear data evaluation methodology including estimates of covariances journal January 2010
Applying a Template of Expected Uncertainties to Updating 239Pu(n,f) Cross-section Covariances in the Neutron Data Standards Database journal January 2020
Unrecognized Sources of Uncertainties (USU) in Experimental Nuclear Data journal January 2020
ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data journal December 2011
ENDF/B-VII.0: Next Generation Evaluated Nuclear Data Library for Nuclear Science and Technology journal December 2006

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