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Accession Number DE2012-1045235
Title Rain-Induced Increase in Background Radiation Detected by Radiation Portal Monitors.
Publication Date 2012
Media Count 13p
Personal Author C. S. Blessinger P. A. Hausladen R. J. Livesay T. F. Guzzardo
Abstract A complete understanding of both the steady state and transient background measured by Radiation Portal Monitors (RPMs) is essential to predictable system performance, as well as maximization of detection sensitivity. To facilitate this understanding, a test bed for the study of natural background in RPMs has been established at the Oak Ridge National Laboratory. This work was performed in support of the Second Line of Defense Programs mission to detect the illicit movement of nuclear material. In the present work, transient increases in gamma ray counting rates in RPMs due to rain are investigated. The increase in background activity associated with rain, which has been well documented in the field of environmental radioactivity, originates from the atmospheric deposition of two radioactive daughters of radon-222, namely lead-214 and bismuth-214 (henceforth 222Rn, 214Pb and 214Bi). In this study, rainfall rates recorded by a co-located weather station are compared with RPM count rates and High Purity Germanium spectra. The data verifies these radionuclides are responsible for the dominant transient natural background fluctuations in RPMs. Effects on system performance and potential mitigation strategies are discussed.
Keywords Background radiation
Bismuth 214
Counting rates
Lead 214
Radiation monitors
Radiation portal monitors (RPM)
Radon 222

Source Agency Technical Information Center Oak Ridge Tennessee
NTIS Subject Category 77E - Nuclear Instrumentation
Corporate Author Oak Ridge National Lab., TN.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1226
Contract Number DE-AC05-00OR22725

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