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Title: Neutron angular distribution in plutonium-240 spontaneous fission

Nuclear safeguards applications require accurate fission models that exhibit prompt neutron anisotropy. We observed an anisotropic neutron angular distribution, in the laboratory reference frame, because prompt fission neutrons carry momentum from fully accelerated fission fragments. Furthermore, a liquid organic scintillation detector array was used with pulse shape discrimination techniques to produce neutron-neutron cross-correlation time distributions and angular distributions from spontaneous fission in a 252Cf, a 0.84 g 240Pu eff metal, and a 1.63 g 240Pu eff metal sample. The effect of cross-talk, estimated with MCNPX-PoliMi simulations, is removed from neutron-neutron coincidences as a function of the angle between detector pairs. Fewer coincidences were observed at detector angles near 90°, relative to higher and lower detector angles. As light output threshold increases, the observed anisotropy increases due to spectral effects arising from fission fragment momentum transfer to emitted neutrons. Finally, stronger anisotropy was observed in Cf-252 spontaneous fission prompt neutrons than in Pu-240 neutrons.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering and Radiological Sciences
  2. European Commission at the Joint Research Centre, Ispra (Italy)
Publication Date:
Grant/Contract Number:
NA0002534; NE0000393; LA14-FY14-027-PD2J
Type:
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 830; Journal Issue: C; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
Research Org:
Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA-20)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION; Fission neutron anisotropy; Plutonium; Nuclear safeguards; MCNPX-PoliMi
OSTI Identifier:
1487063
Alternate Identifier(s):
OSTI ID: 1341190

Marcath, Matthew J., Shin, Tony H., Clarke, Shaun D., Peerani, Paolo, and Pozzi, Sara A.. Neutron angular distribution in plutonium-240 spontaneous fission. United States: N. p., Web. doi:10.1016/j.nima.2016.05.064.
Marcath, Matthew J., Shin, Tony H., Clarke, Shaun D., Peerani, Paolo, & Pozzi, Sara A.. Neutron angular distribution in plutonium-240 spontaneous fission. United States. doi:10.1016/j.nima.2016.05.064.
Marcath, Matthew J., Shin, Tony H., Clarke, Shaun D., Peerani, Paolo, and Pozzi, Sara A.. 2016. "Neutron angular distribution in plutonium-240 spontaneous fission". United States. doi:10.1016/j.nima.2016.05.064. https://www.osti.gov/servlets/purl/1487063.
@article{osti_1487063,
title = {Neutron angular distribution in plutonium-240 spontaneous fission},
author = {Marcath, Matthew J. and Shin, Tony H. and Clarke, Shaun D. and Peerani, Paolo and Pozzi, Sara A.},
abstractNote = {Nuclear safeguards applications require accurate fission models that exhibit prompt neutron anisotropy. We observed an anisotropic neutron angular distribution, in the laboratory reference frame, because prompt fission neutrons carry momentum from fully accelerated fission fragments. Furthermore, a liquid organic scintillation detector array was used with pulse shape discrimination techniques to produce neutron-neutron cross-correlation time distributions and angular distributions from spontaneous fission in a 252Cf, a 0.84 g 240Pueff metal, and a 1.63 g 240Pueff metal sample. The effect of cross-talk, estimated with MCNPX-PoliMi simulations, is removed from neutron-neutron coincidences as a function of the angle between detector pairs. Fewer coincidences were observed at detector angles near 90°, relative to higher and lower detector angles. As light output threshold increases, the observed anisotropy increases due to spectral effects arising from fission fragment momentum transfer to emitted neutrons. Finally, stronger anisotropy was observed in Cf-252 spontaneous fission prompt neutrons than in Pu-240 neutrons.},
doi = {10.1016/j.nima.2016.05.064},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = C,
volume = 830,
place = {United States},
year = {2016},
month = {5}
}