Using anisotropies in prompt fission neutron coincidences to assess the neutron multiplication of highly multiplying subcritical plutonium assemblies [electronic resource]

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Bibliographic Details
Online Access: Online Access (via OSTI)
Format: Government Document Electronic eBook
Language:English
Published: Washington, D.C. : Oak Ridge, Tenn. : United States. National Nuclear Security Administration ; distributed by the Office of Scientific and Technical Information, U.S. Department of Energy, 2016.
Description
Abstract:There is a significant and well-known anisotropy between the prompt neutrons emitted from a single fission event; these neutrons are most likely to be observed at angles near 0° or 180° relative to each other. However, the propagation of this anisotropy through different generations of a fission chain re-action has not been previously studied. We have measured this anisotropy in neutron-neutron coincidences from a subcritical highly-multiplying assembly of plutonium metal. The assembly was a 4.5 kg α-phase plutonium metal sphere composed of 94% <sup>239</sup>Pu and 6% <sup>240</sup>Pu by mass. Data were collected using two EJ-309 liquid scintillators and two EJ-299 plastic scintillators. The angular distribution of neutron-neutron coincidences was measured at 90° and 180° and found to be largely isotropic. Simulations were performed using MCNPX-PoliMi of similar plutonium metal spheres of varying sizes and a correlation between the neutron multiplication of the assembly and the anisotropy of neutron-neutron coincidences was observed. In principle, this correlation could be used to assess the neutron multi-plication of an unknown assembly.
Item Description:Published through SciTech Connect.
07/01/2016.
": S0168900216301917"
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment 825 C ISSN 0168-9002 AM.
Mueller, J.; Mattingly, J.
Univ. of Michigan, Ann Arbor, MI (United States)
Physical Description:p. 87-92 : digital, PDF file.