A new digital logarithmic airborne gamma ray spectrometer is designed in this study. The spectrometer adopts a high-speed and high-accuracy logarithmic amplifier （LOGll4） to amplify the pulse signal logarithmically ...A new digital logarithmic airborne gamma ray spectrometer is designed in this study. The spectrometer adopts a high-speed and high-accuracy logarithmic amplifier （LOGll4） to amplify the pulse signal logarithmically and to improve the utilization of the ADC dynamic range because the low-energy pulse signal has a larger gain than the high-energy pulse signal. After energy calibration, the spectrometer can clearly distinguish photopeaks at 239, 352, 583 and 609 keV in the low-energy spectral sections. The photopeak energy resolution of 137Cs improves to 6.75% from the original 7.8%. Furthermore, the energy resolution of three photopeaks, namely, K, U, and Th, is maintained, and the overall stability of the energy spectrum is increased through potassium peak spectrum stabilization. Thus, it is possible to effectively measure energy from 20 keV to 10 MeV.展开更多
Gamma spectrometric method was used to determine the natural radioactivity of the groundwater obtained from hand dug wells in Sango-Ilorin, North Central Nigeria. The purpose of the study is to ascertain whether the g...Gamma spectrometric method was used to determine the natural radioactivity of the groundwater obtained from hand dug wells in Sango-Ilorin, North Central Nigeria. The purpose of the study is to ascertain whether the groundwater radioactivity level in the area that was previously used as a waste dumpsite and farmland poses any significant health hazard to the populace. The main radionuclides analysed in the samples were 226Ra and 22SRa （progenies of 218Su and 232Th respectively）, and the naturally occurring 40K. The activity concentrations of the radionuclides range from 0.02 to 7.35 Bql1 for 226Ra with a mean of 4.04 ± 0.18 Bql-1, 0.009 to 3.98 Bql-1 for 22SRa having a mean of 0.77 - 0.09 Bql-1. 40K concentration ranges from 0.45 to 30.14 Bq1-1 and has a mean of 4.81 ± 0.62 Bql1. The derived Annual Effective Dose received by the population as a result of the ingestion of 40K is estimated to range from 0 to 0.01 mSvy-1 with an average of 0.01 and standard deviation of 0.02 mSvyl; 226Ra ranged from 0 to 0.8 mSvy-1 with an average of 0.41 and standard deviation of 0.23 mSvy-1 and 228Ra ranged from 0 to 1 mSvy-1 with an average of 0.2 and standard deviation of 0.31 mSvy-1. The results show that the calculated average annual effective dose/ingestion dose for some of the wells are above WHO recommended level of 0.1 mSvylfor drinking water but falls within the tolerable level of 1 mSv/yr to the general public for prolonged exposure as recommended by ICRP. Therefore, it is suggested that detailed radiological monitoring be conducted in the area.展开更多
基金Supported by National Natural Science Foundation of China(40904054)National High Technology Research and Development Program 863(2012AA061803)
文摘A new digital logarithmic airborne gamma ray spectrometer is designed in this study. The spectrometer adopts a high-speed and high-accuracy logarithmic amplifier （LOGll4） to amplify the pulse signal logarithmically and to improve the utilization of the ADC dynamic range because the low-energy pulse signal has a larger gain than the high-energy pulse signal. After energy calibration, the spectrometer can clearly distinguish photopeaks at 239, 352, 583 and 609 keV in the low-energy spectral sections. The photopeak energy resolution of 137Cs improves to 6.75% from the original 7.8%. Furthermore, the energy resolution of three photopeaks, namely, K, U, and Th, is maintained, and the overall stability of the energy spectrum is increased through potassium peak spectrum stabilization. Thus, it is possible to effectively measure energy from 20 keV to 10 MeV.
文摘Gamma spectrometric method was used to determine the natural radioactivity of the groundwater obtained from hand dug wells in Sango-Ilorin, North Central Nigeria. The purpose of the study is to ascertain whether the groundwater radioactivity level in the area that was previously used as a waste dumpsite and farmland poses any significant health hazard to the populace. The main radionuclides analysed in the samples were 226Ra and 22SRa （progenies of 218Su and 232Th respectively）, and the naturally occurring 40K. The activity concentrations of the radionuclides range from 0.02 to 7.35 Bql1 for 226Ra with a mean of 4.04 ± 0.18 Bql-1, 0.009 to 3.98 Bql-1 for 22SRa having a mean of 0.77 - 0.09 Bql-1. 40K concentration ranges from 0.45 to 30.14 Bq1-1 and has a mean of 4.81 ± 0.62 Bql1. The derived Annual Effective Dose received by the population as a result of the ingestion of 40K is estimated to range from 0 to 0.01 mSvy-1 with an average of 0.01 and standard deviation of 0.02 mSvyl; 226Ra ranged from 0 to 0.8 mSvy-1 with an average of 0.41 and standard deviation of 0.23 mSvy-1 and 228Ra ranged from 0 to 1 mSvy-1 with an average of 0.2 and standard deviation of 0.31 mSvy-1. The results show that the calculated average annual effective dose/ingestion dose for some of the wells are above WHO recommended level of 0.1 mSvylfor drinking water but falls within the tolerable level of 1 mSv/yr to the general public for prolonged exposure as recommended by ICRP. Therefore, it is suggested that detailed radiological monitoring be conducted in the area.
