Exploiting fission chain reaction dynamics to image fissile materials

Pete Chapman; Jonathan Mueller; Jason Newby; John Mattingly

doi:10.1016/j.nima.2019.05.001

Exploiting fission chain reaction dynamics to image fissile materials

Pete Chapman, Jonathan Mueller, Jason Newby, John Mattingly

Neutrino Research

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

Radiation imaging is one potential method to verify nuclear weapons dismantlement. We present a method to discriminate between non-multiplying and multiplying neutron sources using a neutron coded aperture imaging system. This method applies time-correlated pulse-height (TCPH) analysis to identify neutrons in fission chain reactions and recreate images using only these events. This analysis was applied to measurements of weapons-grade plutonium (WGPu) metal and ²⁵²Cf performed at the Nevada National Security Site (NNSS) Device Assembly Facility in July 2015. The results demonstrate it is possible to eliminate the non-fissile ²⁵²Cf source from the image while preserving the fissile WGPu source. TCPH analysis was also applied to additional scenes in which the WGPu and ²⁵²Cf sources were measured individually. The results of these separate measurements further demonstrate the ability to remove the non-fissile ²⁵²Cf source and retain the fissile WGPu source. Simulations performed using MCNPX-PoliMi indicate that in a one hour measurement, hollow WGPu spheres are retained at a 1σ level for neutron multiplications M≃2.7 and above. This work has potential application to dismantlement verification where it may be valuable to verify that all neutron sources in an image are multiplying.

Original language	English
Pages (from-to)	198-206
Number of pages	9
Journal	Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume	935
DOIs	https://doi.org/10.1016/j.nima.2019.05.001
State	Published - Aug 11 2019

Funding

This manuscript has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://www.energy.gov/downloads/doe-public-access-plan ). We would like to thank Sandia National Laboratories for their assistance in measuring a 252 Cf source and providing an MCNPX-PoliMi model of the NCAI. This work was sponsored in part by the NNSA Office of Defense Nuclear Nonproliferation R&D through the Consortium for Verification Technology (CVT), United States , grant number DE-NA0002534 .

Funders	Funder number
US Department of Energy
U.S. Department of Energy
Office of Defense Nuclear Nonproliferation	DE-NA0002534

Keywords

Disarmament verification
Neutron coded aperture imaging
Special nuclear material
Time-correlated pulse-height analysis

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10.1016/j.nima.2019.05.001

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title = "Exploiting fission chain reaction dynamics to image fissile materials",

abstract = "Radiation imaging is one potential method to verify nuclear weapons dismantlement. We present a method to discriminate between non-multiplying and multiplying neutron sources using a neutron coded aperture imaging system. This method applies time-correlated pulse-height (TCPH) analysis to identify neutrons in fission chain reactions and recreate images using only these events. This analysis was applied to measurements of weapons-grade plutonium (WGPu) metal and 252Cf performed at the Nevada National Security Site (NNSS) Device Assembly Facility in July 2015. The results demonstrate it is possible to eliminate the non-fissile 252Cf source from the image while preserving the fissile WGPu source. TCPH analysis was also applied to additional scenes in which the WGPu and 252Cf sources were measured individually. The results of these separate measurements further demonstrate the ability to remove the non-fissile 252Cf source and retain the fissile WGPu source. Simulations performed using MCNPX-PoliMi indicate that in a one hour measurement, hollow WGPu spheres are retained at a 1σ level for neutron multiplications M≃2.7 and above. This work has potential application to dismantlement verification where it may be valuable to verify that all neutron sources in an image are multiplying.",

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doi = "10.1016/j.nima.2019.05.001",

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N2 - Radiation imaging is one potential method to verify nuclear weapons dismantlement. We present a method to discriminate between non-multiplying and multiplying neutron sources using a neutron coded aperture imaging system. This method applies time-correlated pulse-height (TCPH) analysis to identify neutrons in fission chain reactions and recreate images using only these events. This analysis was applied to measurements of weapons-grade plutonium (WGPu) metal and 252Cf performed at the Nevada National Security Site (NNSS) Device Assembly Facility in July 2015. The results demonstrate it is possible to eliminate the non-fissile 252Cf source from the image while preserving the fissile WGPu source. TCPH analysis was also applied to additional scenes in which the WGPu and 252Cf sources were measured individually. The results of these separate measurements further demonstrate the ability to remove the non-fissile 252Cf source and retain the fissile WGPu source. Simulations performed using MCNPX-PoliMi indicate that in a one hour measurement, hollow WGPu spheres are retained at a 1σ level for neutron multiplications M≃2.7 and above. This work has potential application to dismantlement verification where it may be valuable to verify that all neutron sources in an image are multiplying.

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Exploiting fission chain reaction dynamics to image fissile materials

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