ID 100
Type S - Special purpose quantity
Sub type STD - Standards
Target 92-U-235
Reaction (n,f) (p,f)
Quantity SIG - Cross section
Incident energy 100 MeV - 500 MeV
Accuracy 5 %
Field(s) Standard
Subfield ADS
Accepted date 11-Apr-2018
Status Work in progress
Latest review date 28-Apr-2022



Improvements in the standard cause all measurements relative to that standard to be improved. See Ref. [1].


5% of the cross-section

Justification document

There are discrepancies (see Fig. 24 in section III.E, pp.161-162 of Ref. [1]) between different theoretical calculations, data estimated from the (p,f) reaction, and the only measured data set of U-238(n,f) cross section at those energies [2]. New measurements of absolute cross sections of U-235 or U-238 (n,f) and/or U-235 or U-238 (p,f) reactions in the energy range where pion channels begin to play an important role (100-500 MeV) are needed to solve the discrepancies and to reduce the uncertainties of the Neutron Standards in that energy range.


  1. A.D. Carlson, et al., Evaluation of the Neutron Data Standards, Nuclear Data Sheets 148, 143-188 (2018)
  2. Z.W. Miller, A Measurement of the Prompt Fission Neutron Energy Spectrum for 235U(n,f) and the Neutron-induced Fission Cross Section for 238U(n,f), PhD Thesis, University of Kentucky (2015); https://uknowledge.uky.edu/physastron_etds/29/

Comment from requester

At high-energy the (n,f) cross-section can be inferred with rather low uncertainty from (p,f) cross-section measurements, and thanks to this can be used in the neutron standards evaluation.

Entry status

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

Main recent references

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


  • U-235 measurement performed at n_TOF in 2018


  • B. Marcinkevicius, S. Simakov, V. Pronyaev, 209Bi(n,f) and natPb(n,f) cross sections as a new reference and extension of the 235U, 238U and 239Pu(n,f) standards up to 1 GeV, IAEA Report INDC(NDS)-0681
  • A.D. Carlson et al., Evaluation of the Neutron Data Standards, NDS 148 (2018) 143