Personal Radiation Detector Field Test and Evaluation Campaign Page: 4 of 8
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The point where the source was located was determined by observing where the gross count rate
was the greatest. The maximum time allocated to
Figure 7 - Schematic of Scenario 3 the PRD operator to locate was 2 minutes.
Depending on the exposure/count rate, the PRD
may or may not have set off the alarm during this
The maximum exposure/count rate for gamma
and neutrons, if available, was recorded with the
start and stop times. The tablet operator stood by
the CONEX and recorded the results. The PRD
operator moved onto the next CONEX as shown
in Figure 8. The results recorded were: 1) the
observed horizontal location of the source; 2) the
gamma exposure rate at identified location; 3) the
neutron count rate at identified location; and 4)
the start and stop time.
Figure 8 -- Photograph of Scenario 3a Testing
SCREENING IDENTIFICATION (SCENARIO 3B)
In scenario 3B, the operator used a PRD with identification capability to identify a source after
localization. The Thermo Electron Interceptor was the only PRD with this capability. The sources
were arranged within the CONEXs using the same configuration as in Scenario 3A (see Figure 7).
The PRD operator placed the PRD on the point on the side of the CONEX closest to the source and
was given up to 30 minutes to perform the identification. Spectra were extracted from the PRD and
provided for inclusion into the Bobcat database. The technical objective of this scenario was to
assess the effectiveness of the PRD in identifying threat radionuclide and naturally occurring
radionuclide during screening operations. The data recorded included: 1) the recorded spectra as
applicable; 2) the displayed choice of radioisotopes from the PRD library list; 3) the maximum
exposure/count rate reading (gamma and neutron as applicable); and 4) the start and stop time.
CHOKEPOINT MONITORING (SCENARIO 4)
In scenario 4, a PRD is used to monitor the passage of people. The operator stands at a pedestrian
chokepoint while the concealed source on a person moves toward the operator in a crowd of people
angled at about 450 to each other so that one PRD
operator could not see the other. CONEXs
contained 17,000kg of Naturally Occurring
Radioactive Material (NORM), 1 inch of steel and
12 inches of plywood as shielding material, or no
shielding. The sources were placed in the
CONEXs along the midline at lm height.
The PRD operator held the PRD in hand and
walked in one direction along the side of the
CONEX, surveying along a line marked on the
outside of the CONEX on the plane of the source.
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Chris A. Hodge, Ding Yuan, Raymond P. Keegan, Michael A. Krstich. Personal Radiation Detector Field Test and Evaluation Campaign, article, July 9, 2007; United States. (digital.library.unt.edu/ark:/67531/metadc897116/m1/4/: accessed August 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.