RESUMO
A study of the influence of moisture content on the radon exhalation rate from phosphate samples (with and without consideration of the back diffusion effect) was performed using the sealed cup technique. The mass exhalation rate was found to increase with an increase in moisture content, reaching a maximum value of 2.414 ± 0.034 Bq kg-1 h-1 with a moisture content of 10%. However, the mass exhalation rate decreased with a continued increase in moisture content above 25%. The mass exhalation rate was also measured at different temperatures between -10 and 50°C. The obtained results show that the mass exhalation rate increases linearly with temperature. We point out that all the obtained values of radon exhalation rate are lower than the world average radon exhalation rate (57.6 Bq m-2 h-1).
Assuntos
Monitoramento de Radiação , Radônio , Radônio/análise , Temperatura , Fosfatos , Água , Expiração , Monitoramento de Radiação/métodosRESUMO
Airborne gamma-ray spectrometry system HELINUC™ is used for different missions. Although well-developed for estimation of high energy emitters' activity, it is rarely used for low energy emitters. A new method for the determination of Am-241 activity over extended sites based both on statistical analysis of spectra and deconvolution of Am-241 signal with a reference library is presented. Results show a lowering of the detection threshold and a good agreement with ground level measurements.
Assuntos
Poluentes Radioativos do Ar/análise , Amerício/análise , Monitoramento de Radiação/métodos , Espectrometria gama/métodos , Contaminação Radioativa do Ar/análise , Aeronaves , Simulação por Computador , França , Humanos , Limite de Detecção , Monitoramento de Radiação/instrumentação , Monitoramento de Radiação/estatística & dados numéricosRESUMO
One of the features of the spectra obtained by airborne gamma spectrometry is the low counting statistics due to a short acquisition time (1 s) and a large source-detector distance (40 m) which leads to large statistical fluctuations. These fluctuations bring large uncertainty in radionuclide identification and determination of their respective activities from the window method recommended by the IAEA, especially for low-level radioactivity. Different types of filter could be used on spectra in order to remove these statistical fluctuations. The present work compares the results obtained with filters in terms of errors over the whole gamma energy range of the filtered spectra with the window method. These results are used to determine which filtering technique is the most suitable in combination with some method for total stripping of the spectrum.
Assuntos
Poluentes Radioativos do Ar/análise , Monitoramento de Radiação/métodos , Espectrometria gama/métodos , AlgoritmosRESUMO
Airborne γ-ray spectrometry with NaI(Tl) is a recognized tool for emergency mapping. The maps produced usually look for natural isotopes ((40)K, (238)U, (232)Th) and (137)Cs due to the Chernobyl accident. Nowadays a new thematic emerges as nuclear materials tracking. Such materials emitting at low energies require new algorithms and a new method is presented here based on counts observed in two or three spectral windows. Since altitude is an important factor to be taken into account, an improvement is proposed to follow flight altitude changes. An extension to medium energies is proposed and compared to windows methods and to peak detection.