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Request ID34 Type of the request High Priority request
TargetReaction and processIncident EnergySecondary energy or angleTarget uncertaintyCovariance
 26-FE-56 (n,inl) SIG  0.5 MeV-20 MeV Emis spec. See details Y
FieldSubfieldCreated dateAccepted dateOngoing actionArchived Date
 Fission ADMAB and SFR 04-APR-08 12-SEP-08 Y

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Requester: Prof. Massimo SALVATORES at CADARACHE, FR

Project (context): NEA WPEC Subgroup 26

Design phases of selected reactor and fuel cycle concepts require improved data and methods in order to reduce margins for both economical and safety reasons. A first indicative nuclear data target accuracy assessment was made within WPEC Subgroup 26 (SG-26). The assessment indicated a list of nuclear data priorities for each of the systems considered (ABTR, SFR, EPR, GFR, LFR, ADMAB, VHTR, EPR). These nuclear data priorities should all be addressed to meet target accuracy requirements for the integral parameters characterizing those systems (see the accompanying requests originating from SG-26).

Somewhat different requested accuracy is required to meet target accuracies for keff, peak power and void coefficient for the Accelerator-Driven Minor Actinides Burner (ADMAB) and for keff for the Sodium-cooled Fast Reactor in a TRU burning configuration, i.e., with a Conversion Ratio CR<1 (SFR). Details are provided in the OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).

Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties. The weighting factor λ is explained in detail in the accompanying document. Changes from the reference value of λ=1 show the the possible allowance for other target uncertainties. Two cases (A and B) are distinguished for λ≠1 (see Table 24 of the report).

Energy RangeInitial versus target uncertainties (%)
λ=1 λ≠1,a λ≠1,b λ=1 λ≠1,a λ≠1,b λ=1 λ≠1,a λ=1 λ≠1,a λ=1 λ≠1,a
6.07 - 19.6 MeV 13 9 11 13
2.23 - 6.07 MeV 7 4 5 7 3 3
1.35 - 2.23 MeV 25 6 7 10 3 4 7 7 7 4 6 2 2
0.498 - 1.35 MeV 16 8 9 13 3 4 6 8 9 4 5 2 2

Justification document:
OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).

Comment from requester:
Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.

Additional file attached: SG26-report.html

Review comment:
Experimental work was recently completed at IRMM. The impact of the new experimental results is studied at CEA/Cadarache. Uncertainties below 5% will require a major further improvement.

Entry Status:
Work in progress (as of SG-C review of May 2018)

Main recent references:
Please report any missing information to


  • R.O. Nelson et al., Cross-section standards for neutron-induced gamma-ray production in the MeV energy range, ND2004, AIP Conference Proceedings 769 (2004) 838, EXFOR 14118
  • C.M. Castaneda et al., Gamma ray production cross sections from the bombardment of Mg, Al, Si, Ca and Fe with medium energy neutrons, NIM/B 260 (2007) 508, EXFOR 14151
  • Z. Wang et al., Study on coincidence measurement for 56Fe(n,xng) reaction cross section, Atomic Energy Science and Technology 47 (2013) 2177, EXFOR 32720
  • A. Negret et al., Cross-section measurements for the 56Fe(n,xng) reactions, PRC 90 (2014) 034602, EXFOR 23073
  • R. Beyer et al., Inelastic scattering of fast neutrons from excited states in 56Fe, NP A 927 (2014) 41, EXFOR 23134
  • A.M.Daskalakis et al., Quasi-differential elastic and inelastic neutron scattering from iron in the MeV energy range, Annals of Nuclear Energy 110 (2017) 603
  • Ongoing work at University of Kentucky, cf. J.R. Vanhoy et al., Differential Cross Section Measurements at the University of Kentucky -- Adventures in Analysis, NEMEA-7, NEA Report NEA/NSC/DOC(2014)13, p.85
  • related measurement by A. Negret, et al., Cross-section measurements for the 57Fe(n,ng)57Fe and 57Fe(n,2ng)56Fe reactions, PRC 96 (2017) 024620 - See section C which discusses the 847keV gamma production cross section in the 57Fe(n,2n) reaction. This contributes (above En=8-9 MeV) to the 847keV gamma production cross section in natFe(n,n') and therefore may represent a source of uncertainty for the 56Fe(n,inl) measurements performed with natFe targets.
  • related measurement by A. Olacel, et al., Neutron inelastic scattering on 54Fe, Eur. Phys. J. A 54 (2018) 183
  • E. Pirovano, et al., Cross section and neutron angular distribution measurements of neutron scattering on natural iron, PRC 99 (2019) 024601



  • C. Jouanne, Sensitivity of the Shielding Benchmarks on Variance-covariance Data for Scattering Angular Distributions, Nuclear Data Sheets 118 (2014) 384
  • I. Kodeli, A. Trkov, G. Zerovnik, Benchmark analysis of iron neutron cross-sections, Jozef Stefan Institute, Ljubljana, Slovenia, Report IJS-DP-11544 (2014)
  • M. Salvatores, et al., Methods and Issues for the Combined Use of Integral Experiments and Covariance Data: Results of a NEA International Collaborative Study, Nuclear Data Sheets 118 (2014) 38
  • G. Palmiotti, et al., Combined Use of Integral Experiments and Covariance Data, Nuclear Data Sheets 118 (2014) 596
  • A. Shaw, et al., Validation of Continuous-Energy ENDF/B-VIII.0 16O, 56Fe, and 63,65Cu Cross Sections for Nuclear Criticality Safety Applications, Nuclear Science and Engineering 195 (2021) 412