Neutron-induced 235U fission spectrum measurements using liquid organic scintillation detectors

Andreas Enqvist, Brian M. Wieger, Lu Huang, Marek Flaska, Sara A. Pozzi, Robert C. Haight, Hye Young Lee, Elaine Kwan, and Ching Yen Wu
Phys. Rev. C 86, 064605 – Published 12 December 2012

Abstract

Measurements have been performed at Los Alamos Neutron Science Center to acquire neutron fission spectra of 235U in the energy range between 0.5 and 10 MeV. These new data complement the currently available experimental data, which are not well known in the energy range below 1 and above 5 MeV. Organic liquid scintillation detectors (EJ-309s) were used together with a digital data-acquisition system. The EJ-309 detectors show excellent pulse shape discrimination capabilities and this is vital for identifying only neutron pulses and rejecting γ-ray pulses. The measurement data show the dependence of average fission neutron energy as a function of the inducing neutron energy. The data agree well with previously published measurements and Watt spectra fits for energies up to tens of MeV. At high fission-inducing neutron energies the spectrum deviates from Watt-spectra fits. The increased energy deposited in higher energy neutron-induced fissions does not significantly increase emitted fission neutron energies for up to 10 MeV. A significant decrease in neutron energy around second-chance fission cannot be observed beyond the current measurement uncertainties.

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  • Received 14 August 2012

DOI:https://doi.org/10.1103/PhysRevC.86.064605

©2012 American Physical Society

Authors & Affiliations

Andreas Enqvist*, Brian M. Wieger, Lu Huang, Marek Flaska, and Sara A. Pozzi

  • Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA

Robert C. Haight and Hye Young Lee

  • Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

Elaine Kwan and Ching Yen Wu

  • Lawrence Livermore National Laboratory, Livermore, California 94551, USA

  • *enqvist@umich.edu

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Vol. 86, Iss. 6 — December 2012

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