Gamma ray spectra simulation and optimization in neutron activation analysis

A software package for the simulation of neutron activation spectra has been developed. The simulation of the 14 MeV neutron activation gamma ray spectra has been carried out both for cyclic and conventional modes. The simulation allows the prediction of the optimum parameters for a low level of detection. The parameters are irradiation, counting and decay times. The simulation was based on an accurate calculation of various parameters such as the photoelectric yield, detector efficiency and background estimation. Compton effect, single and double escape are also taken into account. This software was extensively tested using the IAEA certified material Sll lake sediment and AI(OH)3 chemical standard. A high agreement between the theoretical simulated spectra and those measured is obtained. The second part of the package implements the optimization of the timing parameters. The Monte Carlo method was used to search within a constrained time space for the optimum condition resulting in the lowest detection limit for a given reaction. In order to illustrate the validity of the optimisation routine, sodium is determined in SL1 using the reaction 23Na(n,u)20F

Neutron activation analysis of certified samples by the absolute method

The nuclear reactions analysis technique is mainly based on the relative method or the use of activation cross sections. In order to validate nuclear data for the calculated cross section evaluated from systematic studies, we used the neutron activation analysis technique (NAA) to determine the various constituent concentrations of certified samples for animal blood, milk and hay. In this analysis, the absolute method is used. The neutron activation technique involves irradiating the sample and subsequently performing a measurement of the activity of the sample. The fundamental equation of the activation connects several physical parameters including the cross section that is essential for the quantitative determination of the different elements composing the sample without resorting to the use of standard sample. Called the absolute method, it allows a measurement as accurate as the relative method. The results obtained by the absolute method showed that the values are as precise as the relative method requiring the use of standard sample for each element to be quantified

Neutron activation analysis of certified samples by the absolute method

The nuclear reactions analysis technique is mainly based on the relative method or the use of activation cross sections. In order to validate nuclear data for the calculated cross section evaluated from systematic studies, we used the neutron activation analysis technique (NAA) to determine the various constituent concentrations of certified samples for animal blood, milk and hay. In this analysis, the absolute method is used. The neutron activation technique involves irradiating the sample and subsequently performing a measurement of the activity of the sample. The fundamental equation of the activation connects several physical parameters including the cross section that is essential for the quantitative determination of the different elements composing the sample without resorting to the use of standard sample. Called the absolute method, it allows a measurement as accurate as the relative method. The results obtained by the absolute method showed that the values are as precise as the relative method requiring the use of standard sample for each element to be quantified

Fast neutron spectrometry using thick threshold detectors

This paper discusses the use of thick threshold activation detectors for the characterization of low intensity neutron fields. This technique has been applied to the determination of the spectral emission of a low activity (37 GBq) Am-Be source. The reaction rates induced by the neutrons emitted by this source in different thick metallic targets (Al, Si, Fe, In) have been measured in the following reactions: 27Al(n,p)27Mg, 27Al(n,α)24Na, 28Si(n,p)28Al, 56Fe(n,p)56Mn, 115In(n, n′)115mIn and 115In(n, γ)116mIn. Each measured reaction rate corresponding to a threshold detector response depends on the spectral emission of the source via a correcting factor. This factor, which takes into account the source detector geometry, the neutron attenuation and diffusion by the detectors, has been determined by Monte Carlo simulation using MCNP5 code. The spectral emission of the neutron source has been generated from the response matrix of the threshold detectors by using different neutron spectrum unfolding methods (Stayn'l, Gravel and Maxed). A fairly good agreement with the assumed ISO spectrum has been achieved

Fast neutron spectrometry using thick threshold detectors

This paper discusses the use of thick threshold activation detectors for the characterization of low intensity neutron fields. This technique has been applied to the determination of the spectral emission of a low activity (37 GBq) Am-Be source. The reaction rates induced by the neutrons emitted by this source in different thick metallic targets (Al, Si, Fe, In) have been measured in the following reactions: 27Al(n,p)27Mg, 27Al(n,α)24Na, 28Si(n,p)28Al, 56Fe(n,p)56Mn, 115In(n, n′)115mIn and 115In(n, γ)116mIn. Each measured reaction rate corresponding to a threshold detector response depends on the spectral emission of the source via a correcting factor. This factor, which takes into account the source detector geometry, the neutron attenuation and diffusion by the detectors, has been determined by Monte Carlo simulation using MCNP5 code. The spectral emission of the neutron source has been generated from the response matrix of the threshold detectors by using different neutron spectrum unfolding methods (Stayn'l, Gravel and Maxed). A fairly good agreement with the assumed ISO spectrum has been achieved