End-to-End Simulations of a 3.4-Meter Detector Wall for Neutron-Diagnosed Subcritical Experiments

Journal Article · 29 December 2021 · IEEE Transactions on Nuclear Science

DOI: https://doi.org/10.1109/tns.2021.3139846 · OSTI ID:1834315

Guckes, Amber L. ^[1]; Green, J. Andrew ^[1]; Tinsley, James R. ^[2]; Baldonado, Brandon J. ^[1]

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1. Nevada National Security Site (NNSS), Las Vegas, NV (United States)
2. Nevada National Security Site (NNSS), Santa Barbara, CA (United States). Special Technologies Lab.

The Nevada National Security Site, together with Los Alamos National Laboratory and Lawrence Livermore National Laboratory, is developing a novel diagnostic to measure the reactivity of subcritical experiments. This capability is known as neutron-diagnosed subcritical experiments. The decay of the fission gamma rays from the neutron-interrogated subcritical experiment is measured as a function of time with a large (~3-meter diameter) detector wall consisting of 151 individual detector pixels. The data from this current mode measurement inform the neutron multiplication factor, keff, and thus the relative reactivity of the subcritical experiment. The Nevada National Security Site developed the Gamma Array Simulation Toolkit initially to help inform the design of the individual detector pixels and the 3.4-meter diameter detector wall to be fielded as part of neutron-diagnosed subcritical experiments. This toolkit is now being used to simulate and predict the performance of the final design of the individual detector pixels and the aggregate detector wall. Additionally, key detector characteristics evaluated from these simulations include impulse response, pulse height spectrum, number of photoelectrons per MeV, detector efficiency, and cross talk between detector pixels. Collectively, the results of these simulations inform how well the fission gamma ray die-off distribution from a neutron-diagnosed subcritical experiment measurement can be resolved. This is critical to determining the relative reactivity of the experiment. Furthermore, the Gamma Array Simulation Toolkit can be used to aid in the analysis of the experimental data from a neutron-diagnosed subcritical experiment measurement once the simulation has been benchmarked.

• Research Organization: Nevada National Security Site/Mission Support and Test Services LLC, Las Vegas, NV (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)
• Grant/Contract Number: NA0003624
• OSTI ID: 1834315
• Report Number(s): DOE/NV/03624-1252; STIP WF - 26946646
• Journal Information: IEEE Transactions on Nuclear Science, Journal Name: IEEE Transactions on Nuclear Science Journal Issue: 6 Vol. 69; ISSN 0018-9499
• Publisher: IEEECopyright Statement
• Country of Publication: United States
• Language: English