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Title: Radionuclide identification algorithm for organic scintillator-based radiation portal monitor

Authors:
; ; ;
Publication Date:
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1416082
Grant/Contract Number:
NA-241; NA0002534
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 849; Journal Issue: C; Related Information: CHORUS Timestamp: 2018-01-08 13:33:37; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Paff, Marc Gerrit, Di Fulvio, Angela, Clarke, Shaun D., and Pozzi, Sara A. Radionuclide identification algorithm for organic scintillator-based radiation portal monitor. Netherlands: N. p., 2017. Web. doi:10.1016/j.nima.2017.01.009.
Paff, Marc Gerrit, Di Fulvio, Angela, Clarke, Shaun D., & Pozzi, Sara A. Radionuclide identification algorithm for organic scintillator-based radiation portal monitor. Netherlands. doi:10.1016/j.nima.2017.01.009.
Paff, Marc Gerrit, Di Fulvio, Angela, Clarke, Shaun D., and Pozzi, Sara A. Wed . "Radionuclide identification algorithm for organic scintillator-based radiation portal monitor". Netherlands. doi:10.1016/j.nima.2017.01.009.
@article{osti_1416082,
title = {Radionuclide identification algorithm for organic scintillator-based radiation portal monitor},
author = {Paff, Marc Gerrit and Di Fulvio, Angela and Clarke, Shaun D. and Pozzi, Sara A.},
abstractNote = {},
doi = {10.1016/j.nima.2017.01.009},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = C,
volume = 849,
place = {Netherlands},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.nima.2017.01.009

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  • The necessity to monitor international commercial transportation for illicit nuclear materials resulted in the installation of many nuclear radiation detection systems in Portal Monitors. These were mainly gross counters which alarmed at any indication of high radioactivity in the shipment, the vehicle or even the driver. The innocent alarm rate, due to legal shipments of sources and NORM, or medical isotopes in patients, caused interruptions and delays in commerce while the legality of the shipment was verified. To overcome this difficulty, Department of Homeland Security (DHS) supported the writing of the ANSI N42.38 standard (Performance Criteria for Spectroscopy-Based Portal Monitorsmore » used for Homeland Security) to define the performance of a Portal Monitor with nuclide identification capabilities, called a Spectroscopy Portal Monitor. This standard defines detection levels and response characteristics for the system for energies from 25 keV to3. MeV. To accomplish the necessary performance, several different HPGe detector configurations were modeled using MCNP for the horizontal field of view (FOV) and vertical linearity of response over the detection zone of 5 meters by 4.5 meters for 661 keV as representative of the expected nuclides of interest. The configuration with the best result was built and tested. The results for the FOV as a function of energy and the linearity show good agreement with the model and performance exceeding the requirements of N42.38.« less
  • Many international border crossings screen cargo for illicit nuclear material using radiation portal monitors (RPMs) that measure the gamma-ray flux emitted by vehicles. Screening often consists of primary, which acts as a trip-wire for suspect vehicles, and secondary, which locates the radiation source and performs isotopic identification. The authors present a method of anomaly detection for primary screening that uses past observations of gamma-ray signatures to define an expected benign vehicle population. Newly acquired spectra are then compared to this expected population using statistical criteria that reflect acceptable alarm rates and probabilities of detection. Shown here is an analysis ofmore » spectroscopic RPM data collected at an international border crossing using this technique. The raw data were analyzed to develop an expected benign vehicle population by decimating the original pulse-height channels, extracting composite variables with principal components analysis, and estimating variance-weighted distances from the ''mean vehicle spectra'' with the Mahalanobis distance metric. The following analysis considers data acquired with both NaI(Tl)-based and plastic scintillator-based RPMs. For each system, performance estimates for anomaly sources are compared to common nuisance sources. The algorithm reported here shows promising results in that it is more sensitive to the anomaly sources than common nuisance sources for both RPM types.« less
  • Pacific Northwest National Laboratory (PNNL) has deployed a large array of radiation portal monitors for the Department of Homeland Security U.S. Customs and Border Protection. These portal monitors scan incoming vehicles crossing the U.S. border and shipping containers leaving international ports for radioactive material via gamma-ray and neutron detection. Data produced and captured by these systems are recorded for every vehicle related to radiation signature, sensor/system status, and local background, as well as a host of other variables. Within the Radiation Portal Monitor Project at PNNL, state-of-health observation and analysis for the whole RPM system using these data to determinemore » functionality and performance is being developed. (PIET-43741-TM-492)« less
  • A novel algorithm approach to evaluating data from PVT-based Radiation Portal Monitor (RPM) systems is established. Time series of data from RPMs are evaluated for the presence of sources of interest by comparing the background to the vehicle spectrum at each successive time step, isolating the contribution of anomalous radiation. At each time in the data sequence, a “spectral distance” index is calculated using this method. This method may dramatically reduce systematic fluctuations due to background attenuation by a vehicle (the so-called “shadow shielding” effect), and allow for time-series matched filtering for discrimination of compact anomalous sources. This is attemptedmore » by using a wavelet filter function of similar size to the expected source profile on the output of the spectral distance method. Performance of this method is shown by analysis (injection studies) of a number of real drive-through data sets taken at a U.S. port of entry. Spectra from isotopes of interest are injected into the data set, and the resultant “benign” and “injected” data sets are analyzed with gross-counting, spectral distance, and spatial algorithms. The combination of spectral and spatial analysis methods showed a significant increase to detection performance.« less
  • The time series of data from a Radiation Portal Monitor (RPM) system are evaluated for the presence of point sources by isolating the contribution of anomalous radiation. Energy-windowed background spectra taken from the RPM are compared with the observed spectra at each time step during a vehicle drive-through. The total signal is turned into a spectral distance index using this method. This provides a time series with reduced systematic fluctuations due to background attenuation by the vehicle, and allows for point source detection by time-series analyses. The anomalous time series is reanalyzed by using a wavelet filter function of similarmore » size to the expected source profile. A number of real drive-through data sets taken at a U.S. port of entry are analyzed in this way. A set of isotopes are injected into the data set, and the resultant benign and injected data sets are analyzed with gross-counting, spectral-ratio, and time-based algorithms. Spectral and time methods together offer a significant increase to detection performance.« less