According to the requirements of improving production of Am source used for smoke-sensitice fire alarm making, a method and equipment of its fast relative calibration have been developed. Six measuring equipments have...According to the requirements of improving production of Am source used for smoke-sensitice fire alarm making, a method and equipment of its fast relative calibration have been developed. Six measuring equipments have being successfully applied at production lines of 241Am fire alarm source and factories of automatic smoke-sensitive fire alarm making.展开更多
Several primary factors influencing the alpha energy spectrum of 241Am fire alarm source have been studied in order to get better alpha energy spectrum. The results show that the homogeneity and the thickness of metal...Several primary factors influencing the alpha energy spectrum of 241Am fire alarm source have been studied in order to get better alpha energy spectrum. The results show that the homogeneity and the thickness of metal surface coat and the size of active area of the source have considerable influence on the alpha energy spectrum of the source.展开更多
The safety performance of 241Am fire alarm sources made by using powder metallurgical technology has been preliminarily studied, so as to determine an allowable maximum energy limit value of the alpha particles outgoi...The safety performance of 241Am fire alarm sources made by using powder metallurgical technology has been preliminarily studied, so as to determine an allowable maximum energy limit value of the alpha particles outgoing from this kind of sources in light of radiation safety and the present technology. The yielded results show that 241Am leak has not been found when the peak energy of the alpha energy spectrum of this kind of sources is less than 4.96 MeV.展开更多
Calibrations were performed for three types of neutron ambient dose equivalent rate meters, i.e., Aloka TPS-451C (Hitachi), KSAR1U.06 (Baltic Scientific Instruments), and Model 12-4 (Ludlum), using a standard field of...Calibrations were performed for three types of neutron ambient dose equivalent rate meters, i.e., Aloka TPS-451C (Hitachi), KSAR1U.06 (Baltic Scientific Instruments), and Model 12-4 (Ludlum), using a standard field of a 241Am–Be source. The measured total neutron ambient dose equivalent rates, H*(10)' tot, were analyzed to obtain the direct neutron ambient dose equivalent rates, H*(10)' dir, using the ISO 8529-2-recommended generalized- fit method, semiempirical fit method, and reducedfitting method (RFM) fit methods. The calibration factor (CF), defined as the ratio between the conventional true value of the neutron ambient dose equivalent rates in a free field, H*(10)' FF, and H*(10)' dir, was evaluated as one of the important characteristics of the neutron meters in the present work. The fitting results show that the H*(10)' dir values of the meters are in good agreement within the theoretical data within 4%. The averaged CFs of the three neutron meters were evaluated as 0:99 ± 0:01, 1:00 ± 0.03;and 0:99 ± 0:08, respectively. The largest standard uncertainty of these values was determined to be approximately 18.47%(k =1). The standard uncertainty of the CFs obtained using the RFM method was less than 4.23%(k=1), which is the smallest uncertainty among the three methods.展开更多
Background The neutron activation analysis(NAA)is a very powerful method for multi-element analysis of samples.NAA technique needs to be developed for low neutron flux in millicuries using the 241Am-Be neutron source....Background The neutron activation analysis(NAA)is a very powerful method for multi-element analysis of samples.NAA technique needs to be developed for low neutron flux in millicuries using the 241Am-Be neutron source.Aims To optimize sample and neutron source geometry for maximumγ-ray yield for neutron activation analysis.Method Gamma ray neutron activation analysis(NAA)has been set up where a 50-millicurie Am-Be neutron source is available.In this experimental setup,the neutron source is placed at the center of a cylindrical water tank of 40 x 40 cm in xyz plan,and thermal neutrons are produced at a distance of 1.2 cm from the source.The system is used for the activation analysis of sodium carbonate,sodium chloride and copper with the gamma ray emissions of 1.37,1.73,2.25 and 2.76 MeV for 24Na and 0.511 MeV for 64Cu having half lives of 15 hrs and 12.9 hrs,respectively.The thermal neutron activation analysis has been demonstrated by placing the samples at about 1.2 cm from the neutron source.HPGe and 3x3 inch NaI(Tl)gamma ray spectrometers have been used for the gamma ray spectrometry of these activated samples with the use of a Marinelli beaker.The geometry of the sample with respect to the neutron source has been optimized for the maximumγ-ray yield in NAA.Conclusion The geometry of the sample with respect to the neutron source has been optimized for the maximumγ-ray yield in NAA.The increase in gamma ray flux distribution in the medium of water,due to the neutron source inside the tank,has been observed by a GM detector which is due to the production of short-lived 16N on activation of 16O in water.This system can also be used for promptγ-ray analysis.展开更多
文摘According to the requirements of improving production of Am source used for smoke-sensitice fire alarm making, a method and equipment of its fast relative calibration have been developed. Six measuring equipments have being successfully applied at production lines of 241Am fire alarm source and factories of automatic smoke-sensitive fire alarm making.
文摘Several primary factors influencing the alpha energy spectrum of 241Am fire alarm source have been studied in order to get better alpha energy spectrum. The results show that the homogeneity and the thickness of metal surface coat and the size of active area of the source have considerable influence on the alpha energy spectrum of the source.
文摘The safety performance of 241Am fire alarm sources made by using powder metallurgical technology has been preliminarily studied, so as to determine an allowable maximum energy limit value of the alpha particles outgoing from this kind of sources in light of radiation safety and the present technology. The yielded results show that 241Am leak has not been found when the peak energy of the alpha energy spectrum of this kind of sources is less than 4.96 MeV.
基金supported by the Ministry of Science and Technology of Vietnam under Grant 07/HD/DTCB
文摘Calibrations were performed for three types of neutron ambient dose equivalent rate meters, i.e., Aloka TPS-451C (Hitachi), KSAR1U.06 (Baltic Scientific Instruments), and Model 12-4 (Ludlum), using a standard field of a 241Am–Be source. The measured total neutron ambient dose equivalent rates, H*(10)' tot, were analyzed to obtain the direct neutron ambient dose equivalent rates, H*(10)' dir, using the ISO 8529-2-recommended generalized- fit method, semiempirical fit method, and reducedfitting method (RFM) fit methods. The calibration factor (CF), defined as the ratio between the conventional true value of the neutron ambient dose equivalent rates in a free field, H*(10)' FF, and H*(10)' dir, was evaluated as one of the important characteristics of the neutron meters in the present work. The fitting results show that the H*(10)' dir values of the meters are in good agreement within the theoretical data within 4%. The averaged CFs of the three neutron meters were evaluated as 0:99 ± 0:01, 1:00 ± 0.03;and 0:99 ± 0:08, respectively. The largest standard uncertainty of these values was determined to be approximately 18.47%(k =1). The standard uncertainty of the CFs obtained using the RFM method was less than 4.23%(k=1), which is the smallest uncertainty among the three methods.
文摘Background The neutron activation analysis(NAA)is a very powerful method for multi-element analysis of samples.NAA technique needs to be developed for low neutron flux in millicuries using the 241Am-Be neutron source.Aims To optimize sample and neutron source geometry for maximumγ-ray yield for neutron activation analysis.Method Gamma ray neutron activation analysis(NAA)has been set up where a 50-millicurie Am-Be neutron source is available.In this experimental setup,the neutron source is placed at the center of a cylindrical water tank of 40 x 40 cm in xyz plan,and thermal neutrons are produced at a distance of 1.2 cm from the source.The system is used for the activation analysis of sodium carbonate,sodium chloride and copper with the gamma ray emissions of 1.37,1.73,2.25 and 2.76 MeV for 24Na and 0.511 MeV for 64Cu having half lives of 15 hrs and 12.9 hrs,respectively.The thermal neutron activation analysis has been demonstrated by placing the samples at about 1.2 cm from the neutron source.HPGe and 3x3 inch NaI(Tl)gamma ray spectrometers have been used for the gamma ray spectrometry of these activated samples with the use of a Marinelli beaker.The geometry of the sample with respect to the neutron source has been optimized for the maximumγ-ray yield in NAA.Conclusion The geometry of the sample with respect to the neutron source has been optimized for the maximumγ-ray yield in NAA.The increase in gamma ray flux distribution in the medium of water,due to the neutron source inside the tank,has been observed by a GM detector which is due to the production of short-lived 16N on activation of 16O in water.This system can also be used for promptγ-ray analysis.
