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Request ID18 Type of the request High Priority request
TargetReaction and processIncident EnergySecondary energy or angleTarget uncertaintyCovariance
 92-U-238 (n,inl) SIG  65 keV-20 MeV Emis spec. See details Y
FieldSubfieldCreated dateAccepted dateOngoing actionArchived Date
 Fission Fast Reactors EFR,SFR,ABTR... 28-MAR-08 11-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).

The request for improved cross sections and emission spectra and their accuracies for 238U(n,inel) is an important issue that emerges for five of the eight cases studied. The most stringent requirements for this case arise from the GFR and the LFR.
Improvements of the nuclear data for 238U(n,inel) are important for estimates of keff for the GFR, LFR, ABTR and SFR (in order of significance), the peak power of a GFR and the void coefficient of an SFR.

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 RangeInitial versus target uncertainties (%)
6.07-19.6 MeV 29 12 7
2.23-6.07 MeV 20 3 5 4 2 3
1.35-2.23 MeV 21 4 5 4 2 2
0.498-1.35 MeV 12 7 6 5 2 2
67.4-183 keV 11 7 9 7 4

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:
See appendix A of the attached report. This request is of high priority.

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

Main recent references:
Please report any missing information to



  • A. Santamarina et al., Improvement of 238U Inelastic Scattering Cross Section for an Accurate Calculation of Large Commercial Reactors, ND2013, Nuclear Data Sheets 118 (2014) 118-121
  • R. Capote et al., IAEA CIELO Evaluation of Neutron-induced Reactions on 235U and 238U Targets, NDS 148 (2018) 254