A fully automated gamma-ray spectrometer composed by two coupled HPGe detectors p-type with 60% relative efficiency was developed for monitoring the environmental radioactivity. Through fully automation of operational processes, up to 24 samples can be measured without any human attendance. The absolute efficiency of the MCA_Rad system is estimated by using two point sources 152Eu and 56Co, and validated at 5% relative uncertainty by measuring certified reference materials. The MCA_Rad system was employed in the measurement of the activity concentration of 40K, 226Ra and 232Th in different types of chemical fertilizers used in Albania. The results show a clear correlation between the content of K2O measured and that labeled for chemical fertilizers. The presence of phosphorus in the chemical fertilizer is not clearly related to the activity concentration of 226Ra and 232Th. This is mainly due to the different origins of the phosphate ores and/or to the chemical processing of the ore during fertilizers manufacturing. The activity concentrations of 226Ra and 232Th in NPK samples are found to vary from MDA to 253±14 Bq/kg and MDA to 24±4 Bq/kg, respectively. The calculated radium equivalent activity was found to be comparable or higher than the threshold value of 370 Bq/kg varying from 362 Bq/kg to 967 Bq/kg, mainly due to the high concentration of 40K and 226Ra (especially for NPK-3, NPK-8 and NPK-9). Based on these results, no direct estimations on dose rate can be made, but we recommend to monitor the radiation exposure rate of workers in a storage warehouse.
Natural radioactivity in chemical fertilizers used in Albania investigated with a fully automated gamma-ray spectrometer.
XHIXHA, Gerti;CALLEGARI, IVAN;FIORENTINI, Giovanni;MANTOVANI, Fabio;STRATI, Virginia;
2013
Abstract
A fully automated gamma-ray spectrometer composed by two coupled HPGe detectors p-type with 60% relative efficiency was developed for monitoring the environmental radioactivity. Through fully automation of operational processes, up to 24 samples can be measured without any human attendance. The absolute efficiency of the MCA_Rad system is estimated by using two point sources 152Eu and 56Co, and validated at 5% relative uncertainty by measuring certified reference materials. The MCA_Rad system was employed in the measurement of the activity concentration of 40K, 226Ra and 232Th in different types of chemical fertilizers used in Albania. The results show a clear correlation between the content of K2O measured and that labeled for chemical fertilizers. The presence of phosphorus in the chemical fertilizer is not clearly related to the activity concentration of 226Ra and 232Th. This is mainly due to the different origins of the phosphate ores and/or to the chemical processing of the ore during fertilizers manufacturing. The activity concentrations of 226Ra and 232Th in NPK samples are found to vary from MDA to 253±14 Bq/kg and MDA to 24±4 Bq/kg, respectively. The calculated radium equivalent activity was found to be comparable or higher than the threshold value of 370 Bq/kg varying from 362 Bq/kg to 967 Bq/kg, mainly due to the high concentration of 40K and 226Ra (especially for NPK-3, NPK-8 and NPK-9). Based on these results, no direct estimations on dose rate can be made, but we recommend to monitor the radiation exposure rate of workers in a storage warehouse.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
