ID 112
Target 53-I-127
Reaction (n,2n)
Quantity SIG/SPA - Cross section averaged over an incident particle energy spectrum
Incident energy 239Pu(n,f)
Accuracy 3 %
Field(s) Fission
Subfield Dosimetry
Accepted date 06-Jun-2018
Status Work in progress
Latest review date 22-Apr-2022



A better knowledge of the prompt fission neutron spectrum (PFNS) from Pu-239 thermal-neutron induced fission is important for high-burnup fuels and new generation reactors. This is especially true when considering neutron radiation damage from the PFNS high-energy tail, which can be improved thanks to the measurements of spectrum-averaged cross section (SACS) of well-known high-threshold dosimetry reactions.
Deficiency in Pu-239(n,f) PFNS at large outgoing energies may be responsible for the discrepancies shown in Fig. 178 above 7.5 MeV of average reaction energy, see Fig. 178 in Ref. [1].


3% cross-section ratio uncertainty relative to reference cross sections

Justification document

No SACS measurements exist in Pu-239(nth,f) prompt neutron field. In the latest IAEA evaluation, the extrapolation of Pu-239(nth,f) PFNS to outgoing energies above 8 MeV is based on SACS estimated by interpolation between SACS measured in U-233, U-235 and Cf-252 prompt neutron fields, see page 74-76, Fig. 43 and Table XXVI in Ref. [2].


  1. D. Brown, et al., ENDF/B-VIII.0: The 8th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data, Nuclear Data Sheets 148 (2018) 1 (http://doi.org/10.1016/j.nds.2018.02.001)
  2. R. Capote et al., Prompt Fission Neutron Spectra of Actinides, Nuclear Data Sheets 131 (2016) 1 (http://doi.org/10.1016/j.nds.2015.12.002)

Comment from requester

SACS measurements of high-threshold dosimetry reactions are requested to improve further the high-energy tail of Pu-239(nth,f) PFNS above 8 MeV of outgoing energy. These measurements should be performed relative to high-threshold reference cross sections: Al-27(n,a), Au-197(n,2n), Ni-58(n,p).

Entry status

Work in progress (as of SG-C review of June 2019)

Main recent references

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