An increasing demand of environmental radioactivity monitoring comes both from the scientific community and from the society. This requires accurate, reliable and fast response preferably from portable radiation detectors. Thanks to recent improvements in the technology, γ-spectroscopy with sodium iodide scintillators has been proved to be an excellent tool for in-situ measurements for the identification and quantitative determination of γ-ray emitting radioisotopes, reducing time and costs. Both for geological and civil purposes not only 40K, 238U, and 232Th have to be measured, but there is also a growing interest to determine the abundances of anthropic elements, like 137Cs and 131I, which are used to monitor the effect of nuclear accidents or other human activities. Among the RAD-MONITOR experiment several detection systems have been developed following the request of fast and portable measurements, and a careful selection of the γ-spectra analysis procedure has been consequently performed. The three windows method, suggested by the IAEA [1] has shown limitations, since it becomes imprecise for short time acquisitions and it suffers the poor intrinsic energetic resolution of NaI(Tl) detector. In particular, the Compton continuum around 137Cs photopeak is generally very intense compared to the intensity of 661 keV γ-line. This translates into long acquisition times. Moreover, the intrinsic energetic resolution of sodium iodide detectors prevents to resolve the doublet at 609 keV (214Bi) and 661 keV (137Cs). This issue can be solved only by post processing the data. In any case the windows analysis method requires a prior knowledge of the presence on site of such radioisotope. As a matter of fact, this method is blind to unexpected radionuclides.
The Non Negative Least Square Applied to the Full Spectrum Analysis
FIORENTINI, Giovanni;MANTOVANI, Fabio;SHYTI, Manjola;XHIXHA, Gerti;
2012
Abstract
An increasing demand of environmental radioactivity monitoring comes both from the scientific community and from the society. This requires accurate, reliable and fast response preferably from portable radiation detectors. Thanks to recent improvements in the technology, γ-spectroscopy with sodium iodide scintillators has been proved to be an excellent tool for in-situ measurements for the identification and quantitative determination of γ-ray emitting radioisotopes, reducing time and costs. Both for geological and civil purposes not only 40K, 238U, and 232Th have to be measured, but there is also a growing interest to determine the abundances of anthropic elements, like 137Cs and 131I, which are used to monitor the effect of nuclear accidents or other human activities. Among the RAD-MONITOR experiment several detection systems have been developed following the request of fast and portable measurements, and a careful selection of the γ-spectra analysis procedure has been consequently performed. The three windows method, suggested by the IAEA [1] has shown limitations, since it becomes imprecise for short time acquisitions and it suffers the poor intrinsic energetic resolution of NaI(Tl) detector. In particular, the Compton continuum around 137Cs photopeak is generally very intense compared to the intensity of 661 keV γ-line. This translates into long acquisition times. Moreover, the intrinsic energetic resolution of sodium iodide detectors prevents to resolve the doublet at 609 keV (214Bi) and 661 keV (137Cs). This issue can be solved only by post processing the data. In any case the windows analysis method requires a prior knowledge of the presence on site of such radioisotope. As a matter of fact, this method is blind to unexpected radionuclides.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
