Prompt Gamma Neutron Activation Analysis System Research Articles

Fluka simulation of PGNAA system for determining heavy metal pollution in the soil sample

Abstract This study presented a self-designed prompt gamma neutron activation analysis (PGNAA) model and used Fluka simulation to simulate the heavy metals (Mn, Cu, Hg, Ni, Cr, Pb) in soil samples. The relationship between the prompt γ -ray yield of each heavy metal and soil thickness, content of heavy metals in the soil, and source distance was obtained. Simulation results show that the prompt γ -ray yield of each heavy metal increases with the increase in soil thickness and reaches saturation at 18 cm. The greater the proportion of heavy metals in the soil, the greater the prompt γ -ray yield. The highest content is approximately 3%, and the change in distance between the neutron source and soil sample does not affect the prompt γ -ray yield of heavy metals.

Study on element detection and its correction in iron ore concentrate based on a prompt gamma-neutron activation analysis system

A prompt gamma-neutron activation analysis (PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.

Set-up of prompt gamma neutron activation analysis system at Kartini reactor

Setup and testing of prompt gamma neutron activation analysis (PGNAA) system by using neutron source from the radial beam-port of Kartini reactor have been done. The method used is an experimental characterization of neutron flux in the radial beam-port then setting up of PGNAA system and determination of elements in a bulk solution sample of salt (NaCl). The PGNAA system configuration consists of the collimator with L/D of 28.9 made from lead placed inside the beam-port, bulk sample with 20cm x 20cm x 43cm in dimension located at 30 cm from outer surface of the beam-port, and NaITl detector. The distance of sample to NaITl detector is 20 cm. The experimental test results show that the elements contained in the sample solution of salt can be detected well. The neutron flux in the outer surface of beam-port was measured using activation foil detector, the result was in the order of 106 n cm-2 s-1 with a cadmium ratio of 14.

The MCNP Simulation of a PGNAA System at TRR-1/M1

The prompt-gamma neutron activation analysis system (PGNAA) has been installed at Thai Research Reactor-1/Modified 1 (TRR-1/M1) since 1999. The purpose of the system is for elemental and isotopic analyses. The system mainly consists of a series of the moderator and collimator, neutron and gamma-ray shielding and the HPGe detector. In this work, the condition of the system is carried out based on the Monte Carlo method using Monte Carlo N-Particle transport code and the experiment. The flux ratios (Φthermal/Φepithermal and Φthermal/Φfast) and thermal neutron flux have been obtained. The simulated prompt gamma rays of the Portland cement sample have been carried out. The simulation provides significant contribution in upgrading the PGNAA station to be available in various applications.

Source substitution and optimization of CBXTM PGNAA analyzer in Kangan cement plant

Prompt Gamma Neutron Activation Analysis (PGNAA) is a powerful nondestructive, elemental analysis tool that make use of the time-based characteristics of a nuclear reaction to enhance the capability for multi-elemental analyses. In the present study, improving the moderator and gamma radiation shield of a CBX™ PGNAA analyzer system in Kangan cement factory, as well as substituting a longer half-life neutron source are investigated by utilizing Monte Carlo simulations. The results of the Monte Carlo simulations indicate that high density polyethylene (HDPE) with a thickness of 5 cm as the moderator and lead with a thickness of 4 cm as the gamma radiation shield are the best alternatives for the intended purposes. The long half-life (∼433 years) of AmBe would provide an almost constant level of neutron source over the lifetime of the equipment (∼20 years) and could be substituted for 252Cf (T1/2 = 2.65 years) as neutron source. Meanwhile AmBe has higher prompt gamma yield than original source which makes it more suitable for PGNAA. Without much complications, the improved system could be implemented in the original CBX™ PGNAA system.

Determination of \(\gamma\)-rays Relative Intensities from the \(^{35}\)Cl\((n, \gamma )^{36}\text{Cl}\) Reaction on Filtered Thermal Neutron Beam

The relative intensities of prompt g-rays from the 35Cl(n, g)36Cl reation with thermal neutron have been used as secondary g-ray intensity standards for the prompt gamma neutron activation analysis (PGNAA) and for nuclear data measurements due to a high capture cross section. The filter neutron technique was applied for producing a thermal neutron beam at the neutron channel No. 4 of the Dalat nuclear research reactor. The neutron flux and Cd-ratio are 8.72 ´ 106 n.cm-2.s-1and 134, respectively, determined by the gold foil activation method. A new PGNAA system with a HPGe detector of 58% relative efficiency and a digital spectrometer was used to detect prompt gamma rays from the 35Cl(n, g)36Cl reaction. In this work, relative intensities of 23 prompt g-rays have been determined on the filtered thermal neutron beam. The present results within accuracy 3.0% or better are in good agreement with literature values and data from previous measurements.

PGNAA system preliminary design and measurement of In-Hospital Neutron Irradiator for boron concentration measurement

A prompt gamma neutron activation analysis (PGNAA) system has been recently developed at the 30-kW research reactor In-Hospital Neutron Irradiator (IHNI) in Beijing. Neutrons from the specially designed thermal neutron beam were used. The thermal flux of this beam is 3.08×106cm−2s−1 at a full reactor power of 30kW. The PGNAA system consists of an n-type high-purity germanium (HPGe) detector of 40% efficiency, a digital spectrometer, and a shielding part. For both the detector shielding part and the neutron beam shielding part, the inner layer is composed of 6Li2CO3 powder and the outer layer lead. The boron-10 sensitivity of the PGNAA system is approximately 2.5cps/ppm. Two calibration curves were produced for the 1–10ppm and 10–50 ppm samples. The measurement results of the control samples were in accordance with the inductively coupled plasma atomic emission spectroscopy (ICP-AES) results.

Monte-carlo simulation of the prompt gamma neutron activation analysis system with a femtosecond laser

The prompt gamma neutron activation analysis (PGNAA) system is a useful tool to detect the concentrations of the various composite elements of a sample by measuring the prompt gammas that are activated by neutrons. The composition in terms of the constituent elements is essential information for the identification of the material species of any unknown object. A PGNAA system initiated by a high-power laser has been designed and optimized by using a Monte-Carlo simulation. In order to improve the signal-to-background ratio, we designed an improved neutron-shielding structure and imposed a proper time window in the analysis. In particular, the yield ratio of nitrogen to carbon in a TNT sample was investigated in detail. These simulation results demonstrate that the gamma rays from an explosive sample under a vast level of background can indeed be identified.

Monte Carlo simulation of pulse pile-up effect in gamma spectrum of a PGNAA system

Abstract We have applied a pile-up Monte Carlo simulation code on gamma spectrum of a prompt gamma neutron activation analysis (PGNAA) system. The code has been run in nonparalyzable mode for a specific geometry of a PGNAA system with 241 Am– 9 Be source and NaI(Tl) detector to obtain the distortion due to “pile-up” in the pulse height of gamma spectrum. The results show that the main background in the nitrogen region of interest (ROI) is due to two pile-ups. We have also evaluated the variation of count rate and total photon sampling over the Monte Carlo spectra. At high count rates, not only the nitrogen ROI but also carbon ROI, and hydrogen peak are disturbed strongly. Comparison between the results of simulations and the experimental spectra has shown a good agreement. The code could be used for other source setups and different gamma detection systems.

The comparison of four neutron sources for Prompt Gamma Neutron Activation Analysis (PGNAA) in vivo detections of boron.

A Prompt Gamma Ray Neutron Activation Analysis (PGNAA) system, incorporating an isotopic neutron source has been simulated using the MCNPX Monte Carlo code. In order to improve the signal to noise ratio different collimators and a filter were placed between the neutron source and the object. The effect of the positioning of the neutron beam and the detector relative to the object has been studied. In this work the optimisation procedure is demonstrated for boron. Monte Carlo calculations were carried out to compare the performance of the proposed PGNAA system using four different neutron sources (241Am/Be, 252Cf, 241Am/B, and DT neutron generator). Among the different systems the 252Cf neutron based PGNAA system has the best performance.

Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection

Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with 14.2 MeV neutrons. To compare the performance of these two units in our present PGNA system, we performed Monte Carlo simulations (MCNP-5; Los Alamos National Laboratory) evaluating the nitrogen reactions produced in tissue-equivalent phantoms and the effects of background interference on the gamma-detectors. Monte Carlo response curves showed increased gamma production per unit dose when using the D-D generator, suggesting that it is the more suitable choice for smaller sized subjects. The increased penetration by higher energy neutrons produced by the D-T generator supports its utility when examining larger, especially obese, subjects. A clinical PGNA analysis design incorporating both neutron generator options may be the best choice for a system required to measure a wide range of subject phenotypes.

Measurement of nitrogen in the body using a commercial PGNAA system—phantom experiments

An industrial prompt-gamma neutron activation analysis (PGNAA) system, originally designed for the real-time elemental analyses of bulk coal on a conveyor belt, has been studied to examine the feasibility of using such a system for body composition analysis. Experiments were conducted to measure nitrogen in a simple, tissue equivalent phantom comprised of 2.7 wt% of nitrogen. The neutron source for these experiments was 365 MBq (18.38 μg) of 252Cf located within an engineered low Z moderator and it yielded a dose rate in the measurement position of 3.91 mSv/h; data were collected using a 2780 cm 3 NaI(Tl) cylindrical detector with a digital signal processor and a 512 channel MCA. Source, moderator and detector geometries were unaltered from the system's standard configuration, where they have been optimized for considerations such as neutron thermalization, measurement sensitivity and uniformity, background radiation and external dose minimization. Based on net counts in the 10.8 MeV PGNAA nitrogen photopeak and its escape peaks the dose dependent nitrogen count rate was 11,600 counts/mSv with an uncertainty of 3.0% after 0.32 mSv (4.9 min), 2.0% after 0.74 mSv (11.4 min) and 1.0% after 3.02 mSv (46.4 min).