Improvements in the Method of Radiation Anomaly Detection by Spectral Comparison Ratios

Journal Article · Fri Apr 01 04:00:00 EDT 2016 · Applied Radiation and Isotopes

DOI:https://doi.org/10.1016/j.apradiso.2015.12.063· OSTI ID:1638576

Pfund, David M. ^[1]; Anderson, K K. ^[2]; Detwiler, Rebecca S. ^[1]; Jarman, Kenneth D. ^[1]; McDonald, Benjamin S. ^[1]; Milbrath, Brian D. ^[1]; Myjak, Mitchell J. ^[1]; Paradis, Nathan C. ^[3]; Robinson, Sean M. ^[1]; Woodring, Mitchell L. ^[1]

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1. BATTELLE (PACIFIC NW LAB)
2. PNNL NW Laboratory
3. United States Navy Space and Naval Warfare Systems Command (SPAWAR)

Algorithms for detecting illicit gamma radiation sources must respond to a wide variety of threat signatures and ignore a wider variety of clutter. Previously, we described the Nuisance-rejection Spectral Comparison Ratio Anomaly Detection (N-SCRAD) method for indicating the presence of threat sources during mobile search operations. Our method relies on the formulation of radiation alarm test statistics applied to detector counts in numerous spectral regions of interest and our test statistics are standardized by local estimates of background variability. In this work we present a new automated procedure for selecting test statistics and specifying the regions of interest based on minimizing detectable count rates of prototype threat spectra at a specified false positive rate using simulated annealing. The new procedure can be applied to configuring the detection algorithm when the prototype threats are many and diverse without significantly compromising the detection sensitivity to any one of them. N-SCRAD makes use of estimates of background variability obtained during a search from prior measurements of background. In applications such estimates made purely from past measurements sometimes do not extrapolate well to current conditions. In this work we present a new method for correcting those estimates to current conditions of the total count rate. We demonstrate that the correction lowers detection thresholds for a specified false positive rate, enabling greater sensitivity to targets. The two proposed improvements to N-SCRAD maximize detection power for the expected variety of possible threats while reducing or maintaining the false positive rate.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1638576
• Report Number(s): PNNL-SA-113268
• Journal Information: Applied Radiation and Isotopes, Journal Name: Applied Radiation and Isotopes Vol. 110
• Country of Publication: United States
• Language: English

Related Subjects

Anomaly detection
Gamma-ray spectroscopy
Radiation monitoring.