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Request ID98 Type of the request High Priority request
TargetReaction and processIncident EnergySecondary energy or angleTarget uncertaintyCovariance
 24-CR-53 (n,g) SIG  1 keV-100 keV  8-10 Y
FieldSubfieldCreated dateAccepted dateOngoing actionArchived Date
 Fission  20-JAN-18 05-FEB-18 Y

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Requester: Dr Roberto CAPOTE NOY at IAEA, AUT

Project (context):


Neutron absorption in the Cr isotopes of structural materials affects the criticality of fast reactor assemblies [Koscheev2017]. These cross sections are also of interest for stellar nucleosynthesis [Kadonis10].


8-10% in average cross-sections and calculated MACS at 10, 30, 100 keV.

Selected criticality benchmarks with large amounts of Cr (e.g., PU-MET-INTER-002, and HEU-COMP-INTER-005/4=KBR-15/Cr) show large criticality changes of the order of 1000 pcm due to 30% change in Cr-53 capture in the region from 1 keV up to 100 keV [Trkov2018]. On the other side different evaluations (e.g., BROND-3.1, ENDF/B-VII.1, ENDF/B-VIII.0 and JEFF-3.3) for Cr-53(n,g) are discrepant by 30% in the same energy region. For Cr-50, evaluated files show better agreement at those energies but they are lower than Mughabghab evaluation of the resonance integral by 35%. These discrepancies are not reflected in estimated uncertainty of the evaluated files (e.g., JEFF-3.3 uncertainty is around 10% which is inconsistent with the observed spread in evaluations). Due to these differences we request new capture data with 8-10% uncertainty to discriminate between different evaluations and improve the C/E for benchmarks containing Chromium and/or SS.

Justification document:

Criticality benchmarks can test different components of stainless steel (SS), including Cr which is a large component of some SS. Currently, a large part of the uncertainty in SS capture seems to be driven by uncertainty in Cr capture [Koscheev2017]. Indeed, some benchmarks highly sensitive to Cr (as a component of SS) indicate a need for much higher capture in Cr for both Pu and U fueled critical assemblies (e.g., HEU-COMP-INTER-005/4=KBR-15/Cr and PU-MET-INTER-002=ZPR-6/10).

Capture in natural Cr is driven by capture on Cr-50 and especially in odd Cr-53.

For Cr-53(n,g) there is a very large spread in MACS(30) values in different libraries compared to recommended KADoNiS 1.0 [Kadonis10] value of 41 +/- 10 mb (the latter is 25% larger). Existing measurements from the 70s are even larger being close to 60 mb with 30% uncertainty.

Note also discrepancies in resonance integrals (in barns) between evaluated libraries and ATLAS [Mughabghab2006] for both Cr-50(n,g) and Cr-53(n,g)

ReactionENDF/B-VII.1BROND-3.1ATLAS 2006
Cr-50(n,g)7.217.2111.7 +/- 0.2

Finally, the re-evaluation for ENDF/B-VIII.0 of the ORNL TOF measurement on enriched Cr-53 target [Guber2011] contradicts the increase suggested in Ref. [Koscheev2017] where preliminary data have been used.

Such contradictions need to be resolved thanks to new measurements and evaluation.


  • [Guber2011] K.H. Guber, et al., Journal of the Korean Physical Society 59(2), 1685-1688, 2011
  • [Kadonis10] KADoNiS 1.0 (
  • [Koscheev2017] V. Koscheev, et al., EPJ Conf. 146, 06025, 2017
  • [Mughabghab2006] S.F. Mughabghab, Atlas of Neutron Resonances, 5th Edition, Elsevier, 2006
  • [Trkov2018] A. Trkov, O. Cabellos and R. Capote, Sensitivity of selected benchmarks to Cr-53 and Cr-50 capture, January 2018

Comment from requester:

- Cr-50(n,g) may be measured by activation or TOF. An accurate activation measurement at 5 and 25 keV may help in solving the puzzle of Cr capture.
- Cr-53(n,g) can only be measured by TOF. There is no publication of the final analysis of the ORNL TOF measurement using enriched Cr-53 sample.
- Lead Slowing Down Spectrometer (LSDS) measurements of Cr-50, Cr-53 and Cr-52 enriched samples and of Cr-nat sample could be extremely important to validate and select a proper evaluation of Cr capture cross section below 100 keV. These measurements are strongly encouraged as complementary to TOF and feasible activation measurements.

Additional file attached: Trkov2018.pdf

Review comment:

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

Main recent references:
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  • V. Koscheev et al., Use the results of measurements on KBR facility for testing of neutron data of main structural materials for fast reactors, EPJ Conferences 146 (2007) 06025