Early detection of radioactive fallout by gamma spectrometry.
Radioactive fallout should be detected as early as possible. A new and efficient method for detection of low-level irradiation from manmade radioactivity is developed. Radiation abnormalities are detectable down to air kerma rates of 0.5 to 1.0 nGy h(-1) for 137Cs and even lower for 131I. For multi-gamma energy radioactivity the detection level is 2.6-3.5 nGy h(-1). A standard NaI detector and a 512-channel analyser are used together with noise adjusted singular value decomposition (NASVD). Statistical noise is removed and the measured spectra are reproduced using spectral components produced by NASVD. Stripping is not used and false alarms due to washout of atmospheric radon progeny are almost eliminated. Detection levels and the criteria for setting warning and alarm levels are discussed. The method may also be useful in other situations, for example where low-level signals from radioactive sources need to be detected.
Aage
H K
HK
Measurement and Instrumentation Systems, Orsted-DTU, Building 327, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark. hka@oersted.dtu.dk
Korsbech
U
U
Bargholz
K
K
D000465:Algorithms; D003718:Denmark; D004784:Environmental Monitoring / Q000379:methods*; D011835:Radiation Protection / Q000379:methods*; D011847:Radioactive Fallout / Q000032:analysis*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012637:Security Measures; D012680:Sensitivity and Specificity; D013051:Spectrometry, Gamma / Q000379:methods*; D013269:Stochastic Processes
D011847:Radioactive Fallout