Neutron multiplicity ,easurements With ³He alternative: Straw neutron detectors

Journal Article · Tue Jan 27 00:00:00 EST 2015 · Nuclear Technology

DOI:https://doi.org/10.13182/NT14-12· OSTI ID:1249114

Mukhopadhyay, Sanjoy ^[1]; Wolff, Ronald S. ^[1]; Meade, John A. ^[1]; Detweiler, Ryan ^[1]; Maurer, Richard J. ^[1]; Mitchell, Stephen E. ^[2]; Guss, Paul P. ^[3]; Lacy, Jeffrey L. ^[4]; Sun, Liang ^[4]; Athanasiades, Athanasios ^[4]

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1. National Security Technologies, LLC. (NSTec), Andrews AFB, MD (United States). Remote Sensing Lab. - Andrews
2. National Security Technologies, LLC. (NSTec), Las Vegas, NV (United States). North Las Vegas Operations
3. National Security Technologies, LLC. (NSTec), Las Vegas, NV (United States). Remote Sensing Lab. - Nellis
4. Proportional Technologies, Inc., Houston, TX (United States)

Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using ¹⁰B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions of neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of ³He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used ¹⁰B (in the form of enriched boron carbide: ¹⁰B₄C) for neutron detection instead of ³He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect neutron multiplicity information from spontaneous fission sources using a single panel consisting of 60 straws equally distributed over three rows in high-density polyethylene moderator. In the following year, we developed the field-programmable gate array and associated DAQ software. Finally, this SDRD effort successfully produced a prototype NMC with ~33% detection efficiency compared to a commercial fission meter.

• Research Organization: National Security Technologies, LLC. (NSTec), Andrews AFB, MD (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-06NA25946
• OSTI ID: 1249114
• Report Number(s): DOE/NV/25946-1774
• Journal Information: Nuclear Technology, Vol. 190, Issue 1; ISSN 0029-5450
• Publisher: American Nuclear Society (ANS)
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
neutron multiplicity
fission meter
straws
poisson distribution
field-programmable gate array (FPGA)