ID 29
Target 11-Na-23
Reaction (n,inl)
Quantity SIG - Cross section
Incident energy 0.5 MeV - 1.3 MeV
Accuracy 4-10 %
Secondary Energy/Angle Emis spec.
Field(s) Fission
Subfield Fast Reactors (SFR)
Accepted date 12-Sep-2008
Status Archived
Latest review date 22-Apr-2022


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).

Requested accuracy is required to meet target accuracy for void coefficient 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.

Energy Range Target versus initial uncertainties (%)
  Initial ABTR SFR EFR
1.35 - 2.23 MeV 13 9
0.498 - 1.35 MeV 28 10 4 8

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.

Entry status

Work in progress (as of SG-C review of May 2018)
Pending new evaluation or validation (as of SG-C review of June 2019)
Completed (as of SG-C review of May 2021) - The Na-23 inelastic scattering cross section has been accurately measured at JRC-Geel [Rouki, 2012]. In the framework of the ASTRID SFR project a new evaluation based on both differential and integral information has been prepared for JEFF-3.2 [Archier, 2011, 2014] and adopted in JEFF-3.3 with uncertainties matching the request.

Main recent references

Please report any missing information to hprlinfo@oecd-nea.org



  • S. Kopecky and A. Plompen, R-matrix analysis of the total and inelastic scattering cross sections, EUR 25067 EN (2011)
  • M. Herman et al., COMMARA-2.0 Neutron Cross-Section Covariance Library, Report BNL- 94830-2011, Brookhaven National Laboratory (2011)
  • P. Archier et al., 23Na evaluation with CONRAD for fast reactor applications, Journal of Korean Physical Society 59 (2011) 915
  • P. Archier et al., New JEFF-3.2 Sodium Neutron Induced Cross-sections Evaluation for Neutron Fast Reactors Applications: from 0 to 20 MeV, NDS 118 (2014) 140
  • D. Rochman et al., On the evaluation of 23Na neutron-induced reactions and validations, NIM A 612 (2010) 374
  • Evaluation work in the framework of INDEN (CIELO follow-up), see Summary Report of the IAEA CM, 15-17 May 2019, Vienna, Report INDC(NDS)-0788
  • P. Tamagno, et al., New 23Na evaluation in the resolved resonance range taking into account both differential and double differential experiments, EPJ Conf. 239 (2020) 11006