skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Applying a Template of Expected Uncertainties to Updating 239Pu(n,f) Cross-section Covariances in the Neutron Data Standards Database

Journal Article · · Nuclear Data Sheets
ORCiD logo [1];  [2]; ORCiD logo [3];  [4]; ORCiD logo [1];  [5];  [5];  [6];  [7];  [8];  [5]; ORCiD logo [1];  [5];  [5];  [5]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); National Nuclear Security Agency, Washington, DC (United States)
  4. International Atomic Energy Agency, Vienna (Austria)
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  6. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  7. Lawrence Livermore National Laboratory, Livermore, CA 94551-0808, USA
  8. State Corporation Rosatom, Moscow (Russia). PI Atomstandart; International Atomic Energy Agency, Vienna (Austria)

Templates of uncertainties expected in specific measurement types were recently developed. One aim of these templates is to help evaluators in identifying (1) missing or suspiciously low uncertainties and (2) missing correlations between uncertainties of the same and different experiments, when estimating covariances for experimental data employed in their evaluations. These templates also provide realistic estimates of standard deviations and correlations for a particular uncertainty source and measurement type that can be used by evaluators in situations where they are not supplied by the experimenters. This information allows for a more comprehensive uncertainty analysis across all measurements considered in an evaluation and, thus, more realistic evaluated covariances. Here, in this work, we extend a template that is applicable to uncertainties expected in neutron-induced fission, (n,f), cross-section measurements. It is applied to improving covariances of 239Pu(n,f) cross-section measurements in the database underlying the Neutron Data Standards evaluations. This particular example was chosen since this evaluation is primarily based on experimental information. Also, some uncertainties of individual 239Pu(n,f) cross-section experiments in this database were suspected to be underestimated. The evaluated uncertainties obtained after updating the covariances in the database by means of the template indeed do increase compared to their original values. Even more importantly, the evaluated mean values change noticeably. These modified cross sections impact application calculations significantly, as is demonstrated by employing them in simulations of the effective neutron multiplication factor for a few selected critical assemblies. However, this updated evaluated 239Pu(n,f) cross section should not be interpreted as the final one that should replace values of the current Neutron Data Standards project. Evaluations for the Neutron Data Standards of the 239Pu(n,f) cross section must be linked to many other observables included in the associated database, most notably to cross sections for 235U(n,f), but also to those for 10B(n,α), 6Li(n,t), 238U(n,f), and 238U(n,γ), because of included measurements of the 239Pu(n,f) cross section that appear as ratios to these reactions. Some of these other reactions are correlated to further observables in the database. Hence, updating uncertainties of data sets of any of these observables can potentially impact the 239Pu(n,f) cross section. Uncertainties for all measurements of these linked physical observables have to be updated before a comprehensive evaluation of the 239Pu(n,f) cross section and its corresponding uncertainties can be provided.

Research Organization:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89233218CNA000001; AC52-07NA27344
OSTI ID:
1601400
Alternate ID(s):
OSTI ID: 1605061
Report Number(s):
LA-UR-19-23127; LLNL-JRNL-783165; TRN: US2103637
Journal Information:
Nuclear Data Sheets, Vol. 163, Issue C; ISSN 0090-3752
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 7 works
Citation information provided by
Web of Science

References (52)

A new approach to measuring fission cross-section ratios journal May 1982
Absolute measurements of 235U and 239Pu fission cross-sections with photoneutron sources journal January 1978
Fission-Fragment Scattering journal June 1966
Cross Sections for 239 Pu( n , f ) and 241 Pu( n , f ) in the Range E n = 0.01 eV to 200 MeV journal June 2010
A Measurement of the Fission Cross Sections of 239 Pu and 233 U Relative to 235 U journal June 1970
Measurement of the Ratios of Capture and Fission Neutron Cross Sections of 235 U, 238 U, and 239 Pu at 130 to 1400 keV journal June 1970
Simultaneous Measurement of the Neutron Fission and Absorption Cross Sections of Plutonium-239 Over the Energy Region 0.02 eV to 30 keV journal July 1971
A Monte Carlo computer program for the transport of energetic ions in amorphous targets journal August 1980
Further Radiochemical Studies of Fission of the U 2 3 6 * Compound Nucleus journal October 1962
Fission Fragment Backscattering Corrections to Absolute Fission Counting Rate Measurements journal June 1980
International Evaluation of Neutron Cross Section Standards journal December 2009
The uncertainty of counting at a defined solid angle journal May 2015
The fission cross sections of 233U, 234U, 235U, 236U, 237Np 239Pu, 240Pu and 241Pu for 24 keV neutrons journal June 1965
A time projection chamber for high accuracy and precision fission cross-section measurements
  • Heffner, M.; Asner, D. M.; Baker, R. G.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 759 https://doi.org/10.1016/j.nima.2014.05.057
journal September 2014
Fragment Anisotropies in Neutron-, Deuteron-, and Alpha-Particle-Induced Fission journal February 1965
Uncertainty-driven nuclear data evaluation including thermal (n, α ) applied to 59 Ni journal November 2017
Subthreshold Fission Cross Section of 237 Np journal May 2008
Srim-2003 journal June 2004
The Fission Cross Sections of 233 U, 235 U, 238 U and 239 Pu for Neutrons in the Energy Range 0.030 MeV to 3.0 MeV journal August 1957
Unrecognized Sources of Uncertainties (USU) in Experimental Nuclear Data journal January 2020
Data Covariances from R-Matrix Analyses of Light Nuclei journal January 2015
Absolute Neutron Fission Cross Sections of 235 U, 238 U, and 239 Pu at 13.9 and 14.6 MeV journal November 1978
Fission Cross-Section Ratio Measurements of 239 Pu and 233 U to 235 U from 0.24 to 24 keV journal March 1970
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
Directional fast neutron detection using a time projection chamber
  • Bowden, N. S.; Heffner, M.; Carosi, G.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 624, Issue 1 https://doi.org/10.1016/j.nima.2010.09.010
journal December 2010
Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC) journal June 2014
Neutron-Induced Fission of 233 U, 238 U, 232 Th, 239 Pu, 237 Np, nat Pb and 209 Bi Relative to 235 U in the Energy Range 1-200 MeV journal August 2002
Determination of Resonance Parameters and their Covariances from Neutron Induced Reaction Cross Section Data journal December 2012
The Fission Cross Sections of Plutonium-239 and Plutonium-242 Relative to Uranium-235 from 0.1 to 10 MeV journal December 1978
Performance of a MICROMEGAS-based TPC in a high-energy neutron beam
  • Snyder, L.; Manning, B.; Bowden, N. S.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 881 https://doi.org/10.1016/j.nima.2017.10.028
journal February 2018
High Resolution Measurements of Neutron-Induced Fission Cross Sections for 233 U, 235 U, 239 Pu and 241 Pu Below 30 keV journal June 1973
The fission cross sections of 233U, 234U, 236U, 238U, 237Np, 239Pu, 240Pu and 241Pu relative to that of 235U for neutrons in the energy range 1–14 MeV journal August 1967
Measurement of the 239Pu(n,f) cross section from thermal up to 30 keV neutron energy journal January 1980
Assaying of targets for nuclear measurements with a gridded ionization chamber
  • Budtz-Jørgensen, C.; Knitter, H. H.; Bortels, G.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 236, Issue 3 https://doi.org/10.1016/0168-9002(85)90972-6
journal June 1985
The effect of fragment anisotropy on fission-chamber efficiency journal July 1974
Experimental and theoretical investigation of the backscattering of fission fragments journal November 1979
ENDF/B-VII.1 Neutron Cross Section Data Testing with Critical Assembly Benchmarks and Reactor Experiments journal December 2011
Measurement of the Fission Cross Sections of Uranium-233 and Plutonium-239 Relative to Uranium-235 from 1 keV to 30 MeV journal May 1978
DeCE: the ENDF-6 data interface and nuclear data evaluation assist code journal July 2019
Measurement of the Neutron Capture and Fission Cross Sections of 239 Pu and 235 U, 0.02 eV to 200 keV, the Neutron Capture Cross Sections of 197 Au, 10 to 50 keV, and Neutron Fission Cross Sections of 233 U, 5 to 20 journal February 1976
Subthreshold Fission Cross Section of 240 Pu and the Fission Cross Sections of 235 U and 239 Pu journal December 1984
Methods for primary standardization of activity journal August 2007
High-Resolution Fission Cross-Section Measurements of 235 U and 239 Pu journal August 1992
Neutron-Induced Fission Cross-Section Ratios for 239 Pu, 240 Pu, 242 Pu, and 244 Pu Relative to 235 U from 0.5 to 400 MeV journal June 1998
Measurement of the ratio of the239Pu and235U fission cross sections for 0.024-7.4-MeV neutrons journal October 1977
Geant4—a simulation toolkit
  • Agostinelli, S.; Allison, J.; Amako, K.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 506, Issue 3 https://doi.org/10.1016/S0168-9002(03)01368-8
journal July 2003
Measurements of the Neutron Fission and Absorption Cross Sections of 239 Pu Over the Energy Region 0.02 eV to 30 keV journal May 1970
Measurement of the normalized U 238 ( n , f ) / U 235 ( n , f ) cross section ratio from threshold to 30 MeV with the NIFFTE fission Time Projection Chamber journal March 2018
Neutron Fission Cross Sections of 239 Pu and 240 Pu Relative to 235 U journal July 1983
On the impact of the fissile coating on the fission chamber signal
  • Jammes, C.; Filliatre, P.; Loiseau, P.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 681 https://doi.org/10.1016/j.nima.2012.03.032
journal July 2012
Validating nuclear data uncertainties obtained from a statistical analysis of experimental data with the “Physical Uncertainty Bounds” method journal January 2020