NDLI: Accurate modeling of the terrestrial gamma-ray background for homeland security applications

Content Provider	IEEE Xplore Digital Library
Author	Sandness, G.A. Schweppe, J.E. Hensley, W.K. Borgardt, J.D. Mitchell, A.L.
Copyright Year	2009
Description	Author affiliation: Pacific Northwest National Laboratory, Richland, WA 99352 USA (Sandness, G.A.; Schweppe, J.E.; Hensley, W.K.) \|\| Juniata College, Huntingdon, PA 16652 USA (Borgardt, J.D.; Mitchell, A.L.)
Abstract	The Pacific Northwest National Laboratory has developed computer models to simulate the use of radiation portal monitors to screen vehicles and cargo for the presence of illicit radioactive material. The gamma radiation emitted by the vehicles or cargo containers must often be measured in the presence of a relatively large gamma-ray background that is mainly due to the presence of potassium, uranium, and thorium (and progeny isotopes) in the soil and surrounding building materials. This large background is often a significant limit to the detection sensitivity for items of interest and must be modeled accurately for analyzing homeland security situations. Calculations of the expected gamma-ray emission from a disk of soil and asphalt were made using the Monte Carlo transport code MCNP and were compared to measurements made with a thallium-drifted sodium iodide detector. Analysis revealed that the energy spectrum of the measured background could not be reproduced unless the model included gamma rays coming from the ground out to distances of at least 300 m. The contribution from beyond about 50 m was primarily due to gamma rays that scattered in the air before entering the detectors rather than passing directly from the ground to the detectors. These skyshine gamma rays contribute tens of percent to the total gamma-ray spectrum, primarily at energies below a few hundred keV. The techniques that are being developed to efficiently calculate the contributions from a large soil disk and a large air volume in a Monte Carlo simulation are described and the implications of skyshine in portal monitoring applications are discussed.
Starting Page	126
Ending Page	133
File Size	1294391
Page Count	8
File Format	PDF
ISBN	9781424439614
ISSN	10957863
DOI	10.1109/NSSMIC.2009.5401843
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2009-10-24
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Terrorism Gamma rays Soil measurements Gamma ray detection Gamma ray detectors Portals Vehicles Application software Laboratories Computational modeling
Content Type	Text
Resource Type	Article

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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