Abstract
We present a new evaluation of the 239 Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. Selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.
Highlights
A prompt fission neutron spectrum (PFNS) provides the energy distribution of neutrons emitted promptly after fission and before the onset of delayed β-decay
We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons
For Einc = thermal, ENDF/B-VII.1 has a trend to lower PFNS values for Eout ≤ 0.8 MeV compared to the combined Starostov data as well as the current evaluation
Summary
A prompt fission neutron spectrum (PFNS) provides the energy distribution of neutrons emitted promptly after fission and before the onset of delayed β-decay. Significant efforts have been undertaken to provide improved evaluated nuclear data within the framework of an IAEA coordinated research project on PFNS of actinides [1] as well as for the CIELO project [2] and the release of the ENDF/B-library. We present a new evaluation of the 239Pu PFNS induced by neutrons with incident energies from thermal to 30 MeV. This evaluation is currently tested as part of a CIELO prototype file for incident energies above 5 MeV and was distributed to the IAEA CRP [1].
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