Rain-Induced Increase in Background Radiation Detected by Radiation Portal Monitors

Hausladen, Paul¹  Blessinger, Christopher S¹  Guzzardo, Tyler¹  Livesay, Jake¹ 

[1]ORNL

关键词: BACKGROUND RADIATION;    BISMUTH 214;    COUNTING RATES;    DEPOSITION;    DETECTION;    FLUCTUATIONS;    GERMANIUM;    LEAD 214;    MITIGATION;    MONITORS;    RADIATIONS;    RADIOACTIVITY;    RADIOISOTOPES;    RADON 222;    RAIN;    SENSITIVITY;    SPECTRA;    TRANSIENTS;   

DOI  :  10.2172/1045235
RP-ID  :  ORNL/TM-2012/229
PID  :  OSTI ID: 1045235
Others  :  Other: NN5005011
Others  :  MDGA516
Others  :  TRN: US1203657

美国|英语

来源: SciTech Connect

【 摘 要 】

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 Program's 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 {sup 222}Rn, {sup 214}Pb and {sup 214}Bi). 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.