Abstract

A new 238U(n,f) prompt fission neutron spectra (PFNS) measurement has been recently performed at the WNR facility of the Los Alamos National Laboratory. The measurement allows one to explore the dependence of the prompt fission neutron energy spectra on the incident neutron energy. The experimental setup couples the Chi-Nu scintillator array to a newly developed fission chamber, characterized by an improved alphafission discrimination and time resolution, a reduced amount of matter in the neutron beam and a higher actinide mass. The dedicated setup and the high statistics collected allow us to obtain a good precision on the measured fission neutron energy, as well as to explore the low energy region, down to 650keV, and the high energy region, above 5 MeV, of the emitted neutron spectrum. These are indeed the regions where discrepancies in the evaluated PFNS data are found. We present here the first preliminary results of the experiment.

Highlights

  • IntroductionPrompt fission neutron spectra (PFNS) provide valuable information for the understanding of the fission process and represent a key parameter for nuclear energy applications

  • Prompt fission neutron spectra (PFNS) provide valuable information for the understanding of the fission process and represent a key parameter for nuclear energy applications.The experimental database of fission neutron spectra collects few data, far less precise than those on the other fission observables, and presents significant discrepancies especially below 1 MeV and above 5 MeV

  • From a theoretical point of view, microscopic models of fission still do not provide reliable predictions, evaluated PFNS are obtained from phenomenological models

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Summary

Introduction

Prompt fission neutron spectra (PFNS) provide valuable information for the understanding of the fission process and represent a key parameter for nuclear energy applications. The experimental database of fission neutron spectra collects few data, far less precise than those on the other fission observables, and presents significant discrepancies especially below 1 MeV and above 5 MeV. From a theoretical point of view, microscopic models of fission still do not provide reliable predictions, evaluated PFNS are obtained from phenomenological models. To test and validate these models and improve data for applications, precise PFNS measurements are required. Our group, involved since 2000’s in PFNS measurements [1,2,3], has done a special effort to improve the accuracy by developing new dedicated tools. We describe here the last experiment that we performed on 238U PFNS

The experiment
Neutron detection array
Data acquisition system
Data analysis and preliminary results
Conclusions

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