The use of energy windowing to discriminate SNM from NORM in radiation portal monitors

Ely, James H.; Kouzes, Richard T.; Schweppe, John E.; Siciliano, Edward R.; Strachan, Denis M.; Weier, Dennis R.

doi:10.1016/j.nima.2006.01.053

Cited by 119 publications

(69 citation statements)

References 8 publications

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“…Nevertheless, energy windowing techniques have been applied successfully to enhance the sensitivity to threat materials without producing excessive false alarm rates. 2 The application of energy-windowing techniques should benefit from the improved resolution and gain stability of the PVT-NG sensor relative to typical PVT portals. We also evaluated the feasibility of performing isotope identification based on spectra that are acquired with the PVT-NG sensor.…”

Section: Isotope Identificationmentioning

confidence: 99%

Neutron counting and gamma spectroscopy with PVT detectors.

Mitchell¹,

Brusseau²

2011

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Radiation portals normally incorporate a dedicated neutron counter and a gamma-ray detector with at least some spectroscopic capability. This paper describes the design and presents characterization data for a detection system called PVT-NG, which uses large polyvinyl toluene (PVT) detectors to monitor both types of radiation. The detector material is surrounded by polyvinyl chloride (PVC), which emits highenergy gamma rays following neutron capture reactions. Assessments based on high-energy gamma rays are well suited for the detection of neutron sources, particularly in border security applications, because few isotopes in the normal stream of commerce have significant gamma ray yields above 3 MeV. Therefore, an increased count rate for high-energy gamma rays is a strong indicator for the presence of a neutron source. The sensitivity of the PVT-NG sensor to bare 252 Cf is 1.9 counts per second per nanogram (cps/ng) and the sensitivity for 252 Cf surrounded by 2.5 cm of polyethylene is 2.3 cps/ng. The PVT-NG sensor is a proof-of-principal sensor that was not fully optimized. The neutron detector sensitivity could be improved, for instance, by using additional moderator.The PVT-NG detectors and associated electronics are designed to provide improved resolution, gain stability, and performance at high-count rates relative to PVT detectors in typical radiation portals. As well as addressing the needs for neutron detection, these characteristics are also desirable for analysis of the gamma-ray spectra. Accurate isotope identification results were obtained despite the common impression that the absence of photopeaks makes data collected by PVT detectors unsuitable for spectroscopic analysis. The PVT detectors in the PVT-NG unit are used for both gamma-ray and neutron detection, so the sensitive volume exceeds the volume of the detection elements in portals that use dedicated components to detect each type of radiation.

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Section: Isotope Identificationmentioning

confidence: 99%

Neutron counting and gamma spectroscopy with PVT detectors.

Mitchell¹,

Brusseau²

2011

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“…In the current implementation and for multiple radionuclides, the first target coefficient, 1  , is set to unity and the remaining coefficients are evaluated in the LS process along with the PC coefficients. This can be problematic if target spectra associated with the remaining coefficients do not possess an orthogonal component to the PC spectra.…”

Section: Incorporation Of Shielding Effects In the Tpca Solutionmentioning

confidence: 99%

“…The latter is accomplished by the ability to confidently detect and identify cargo with benign sources of radiation at the primary lane without the need to send a vehicle to secondary inspection. Previous studies have explored and demonstrated data transformation methods to differentiate NORM cargo from other nuclides (1)(2) .…”

Section: Introductionmentioning

confidence: 99%

Including shielding effects in application of the TPCA method for detection of embedded radiation sources.

Johnson¹,

Shokair²

2011

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Conventional full spectrum gamma spectroscopic analysis has the objective of quantitative identification of all the radionuclides present in a measurement. For low-energy resolution detectors such as NaI, when photopeaks alone are not sufficient for complete isotopic identification, such analysis requires template spectra for all the radionuclides present in the measurement. When many radionuclides are present it is difficult to make the correct identification and this process often requires many attempts to obtain a statistically valid solution by highly skilled spectroscopists.A previous report investigated using the targeted principal component analysis method (TPCA) for detection of embedded sources for RPM applications. This method uses spatial/temporal information from multiple spectral measurements to test the hypothesis of the presence of a target spectrum of interest in these measurements without the need to identify all the other radionuclides present. The previous analysis showed that the TPCA method has significant potential for automated detection of target radionuclides of interest, but did not include the effects of shielding. This report complements the previous analysis by including the effects of spectral distortion due to shielding effects for the same problem of detection of embedded sources. Two examples, one with one target radionuclide and the other with two, show that the TPCA method can successfully detect shielded targets in the presence of many other radionuclides. The shielding parameters are determined as part of the optimization process using interpolation of library spectra that are defined on a 2D grid of atomic numbers and areal densities.-4-

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“…In some deployments, the gamma counts are coarsely binned into low and high energy channels. In others using plastic scintillator detector material, the gamma counts are less coarsely binned into approximately eight energy channels [2].…”

Section: Introductionmentioning

confidence: 99%

“…Data from these passive RPMs have been collected at various ports of entry since 2003 [2][3][4][5][6]. As a vehicle slowly passes by a set of fixed radiation sensors, a time series of measurements from each sensor is recorded.…”

Section: Introductionmentioning

confidence: 99%

Pass/Fail Criterion for a Simple Radiation

Burr

Gavron²

2012

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One of the simplest tests of a radiation portal monitor (RPM) is a series of n repeats (a vehicle drive-through) in which the i th repeat records a total number of counts X i and alarms if X i ≥ T where T is an alarm threshold. The RPM performance tests we consider use n repeats to estimate the probability p = P(X i ≥ T). This paper addresses criterion A for testing RPMs, where criterion A is: for specified source strength, we must be at least 95% confident that p ≥ 0.5. To assess criterion A, we consider a distribution-free test and a test relying on assuming the counts X i have approximately a Poisson distribution. Both test options require tolerance interval construction.

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The use of energy windowing to discriminate SNM from NORM in radiation portal monitors

Cited by 119 publications

References 8 publications

Neutron counting and gamma spectroscopy with PVT detectors.

Neutron counting and gamma spectroscopy with PVT detectors.

Including shielding effects in application of the TPCA method for detection of embedded radiation sources.

Pass/Fail Criterion for a Simple Radiation

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