Prompt Gamma Ray Neutron Activation Analysis Setup Research Articles

Comparison between NIS and TNC channels for the detection of nickel in soil samples

The prompt gamma-ray neutron activation analysis (PGNAA) is a significant technique for determining the quantities of a variety of elements in natural materials, whether online or in situ, regardless of their chemical compounds. This study focused on evaluating the performance of a portable PGNAA setup based on a Genie 16 DD neutron generator to determine the minimum detectable concentration (MDC) of nickel in soil samples. Two separate reaction mechanisms were used to activate the samples. A CeBr3 detector was used to detect nickel gamma rays at 1331 and 1454 keV caused by neutron inelastic scattering, as well as those at 8553 and 8998 keV emitted following thermal neutron capture activations. The obtained MDC values for both reaction channels have improved as a result of the research.

Improving a PGNAA Technique to Detect Heavy Metals in Solid Samples

Prompt gamma-ray neutron activation analysis (PGNAA) is a useful approach for determining the concentrations of a variety of elements in natural materials, either online or in situ, without affecting their chemical forms in matter. The current research aimed to improve the yield of a portable PGNAA setup using a dc beam of 2.5 MeV neutrons and a CeBr3 detector to record gamma rays from neutron inelastic scatterings. It is impossible to avoid the superimposition of heavy metal gamma rays and those from the detector’s element. However, tests were carried out to improve the signal-to-background ratio. By assessing the minimum detectable concentrations (MDC) of chrome, titanium, and zinc in soil samples, the effectiveness of the new optimization was confirmed. The study shows an improvement in the MDC values.

Research on the optimization method for PGNAA system design based on Signal-to-Noise Ratio evaluation

In this research, for improving the measurement performance of Prompt Gamma-ray Neutron Activation Analysis (PGNAA) set-up, a new optimization method for set-up design was proposed and investigated. At first, the calculation method for Signal-to-Noise Ratio (SNR) was proposed. Since the SNR could be calculated and quantified accurately, the SNR was chosen as the evaluation parameter in the new optimization method. For discussing the feasibility of the SNR optimization method, two kinds of PGNAA set-ups were designed in the MCNP code, based on the SNR optimization method and the previous signal optimization method, respectively. Meanwhile, the single element spectra analysis method was proposed, and the analysis effect of single element spectra as well as element sensitivity were used for comparing the measurement performance. Since the simulation results showed the better measurement performance of set-up designed by SNR optimization method, the experimental set-ups were built for the further testing, finally demonstrating the feasibility of the SNR optimization method for PGNAA set-up design.

Application of the Monte Carlo Library Least-Squares (MCLLS) approach for chromium quantitative analysis in aqueous solution

In the present work, a new in-situ prompt gamma-ray neutron activation analysis (PGNAA) setup was developed for the quantitative measurement of chromium (Cr) in aqueous solutions which consists of a 4" × 4″ inch Bismuth Germanate detector and a 300 mCi 241Americium-beryllium neutron source. A series of standard samples were prepared by dissolving Cr compounds in deionized water of analytical pure grade and measured using the in situ PGNAA setup. Quantitative spectrum analysis was conducted using Monte Carlo Library Least-Squares approach (MCLLS). Simulates of elemental library spectra were in silico modeled using the CEARCPG code, which was developed by Prof. Robin Gardner research group in North Carolina State University. The fitted spectra presented were in excellent agreement with the total experimental spectrum, and the correlation coefficients were all nearly 1. After applying the MCLLS approach, the minimum detectable concentration of Cr was 301.5 mg/L, better than that obtained with other setups, and the relative deviation of the Cr quantitative analysis accuracy was less than 4.09%.

Monte Carlo study of a flexible device for in situ PGNAA using 241Am–Be source: application to total chlorine determination

MCNP5 has been used to optimize the design of a Prompt gamma ray neutron activation analysis (PGNAA) facility, which was subsequently constructed for quantification of total chlorine in water to simulate neutron transport from an 241AmBe source into a PGNAA set-up. Modeling calculations were performed to optimize the experimental set-up for Cl measurements in water. The optimization with MCNP5 was focused on maximizing the thermal neutrons flux which leads to improving the gamma prompt production after neutron capture in a water sample. The influence of dimensions and materials for the neutron collimation as well as the dimensions of the sample together were studied. A PGNAA facility with an 241AmBe neutron source was built based on the optimized configuration and used to determine chlorine concentration. Measured values of the chlorine count rate were plotted versus the NaCl in water. The count rate versus amount of chlorine show a good coefficient of correlation of the linear fit. The result permits PGNAA to be a valuable diagnostic tool for getting an indication of the salinity contamination of water.

Response of a PGNAA setup for pozzolan-based cement concrete specimens

Pozzolanic materials are added to Portland cement concrete to increase its durability, particularly corrosion-resistance. In this study the elemental composition of a pozzolanic cement concrete was measured non-destructively utilizing an accelerator-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup. The optimum size of the pozzolanic cement concrete specimen was obtained through Monte Carlo simulations. The simulation results were experimentally verified through the gamma-ray yield measurement from the pozzolanic cement concrete specimens as a function of their radii. The concentration of the pozzolanic material in the cement concrete specimens was evaluated by measuring gamma-ray yield for calcium and iron from pozzolanic cement concrete specimens containing 5-80 wt% pozzolan. A good agreement was noted between the experimental values and the Monte Carlo simulation results, indicating an excellent response of the KFUPM accelerator-based PGNAA setup for pozzolan based concrete.

Sample to moderator volume ratio effects in neutron yield from a PGNAA setup

Performance of a prompt gamma ray neutron activation analysis (PGNAA) setup depends upon thermal neutron yield at the PGNAA sample location. For a moderator, which encloses a sample, thermal neutron intensity depends upon the effective moderator volume excluding the void volume due to sample volume. A rectangular moderator assembly has been designed for the King Fahd University of Petroleum and Minerals (KFUPM) PGNAA setup. The thermal and fast neutron yield has been measured inside the sample cavity as a function of its front moderator thickness using alpha particle tracks density and recoil proton track density inside the CR-39 nuclear track detectors (NTDs). The thermal/fast neutron yield ratio, obtained from the alpha particle tracks density to proton tracks density ratio in the NTDs, shows an inverse correlation with sample to moderator volume ratio. Comparison of the present results with the previously published results of smaller moderators of the KFUPM PGNAA setup confirms the observation.

Use of 7Li(p,n) reaction as a neutron source in a PGNAA setup

The performance of a 7Li(p,n) reaction-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup has been determined for analysis of Portland cement samples using Monte Carlo study. The calculations were carried out for a 7Li(p,n) reaction-based PGNAA setup with an external moderator similar to the one used in a previous 2.8MeV neutrons-based PGNAA setup. The optimum values of geometry parameters of the 7Li(p,n) reaction-based setup are different from those of the 2.8MeV neutrons-based setup resulting in better performance of the 7Li(p,n) reaction-based setup. The prompt γ-ray yield from the 7Li(p,n) reaction-based setup is 60–70% higher than that from the 2.8MeV neutrons-based setup. Although the performances of the 7Li(p,n) reaction-based setup is comparable with that of a previously studied 3H(p,n) reaction-based setup, yet performance of the 7Li(p,n) reaction-based setup is superior to that of the 3H(p,n) reaction-based setup because it has less radiation hazard due to utilization of non-radioactive neutron producing target. This study has provided a theoretical base for experimental test of a 7Li(p,n) reaction-based PGNAA setup.

Elemental analysis of concrete samples using an accelerator-based PGNAA setup

Elemental analysis of concrete samples was carried out using an accelerator-based prompt gamma ray neutron activation analysis (PGNAA) setup. The gamma rays were produced via the capture of thermal neutron in the concrete sample. The prompt gamma ray yield was measured for 12 cm long concrete samples as a function of sample radius over a range of 6–11.5 cm radii. The optimum yield of the prompt gamma rays from the concrete sample was measured from a sample with 11.5 cm radius. The gamma ray yield was also calculated for 12 cm long concrete samples with 6–11.5 cm radius using Monte Carlo simulations. The experimental results were in excellent agreement with the calculated yield of the prompt gamma rays from the samples. Result of this study has shown the useful application of an accelerator-based PGNAA setup in elemental analysis of concrete sample. The facility can be further used to determine the chloride and sulfate concentrations in concrete samples for corrosion studies of reinforcement steel in concrete structures.

Elemental analysis of concrete samples using an accelerator-based PGNAA setup

Elemental analysis of concrete samples was carried out using an accelerator-based prompt gamma ray neutron activation analysis (PGNAA) setup. The gamma rays were produced via the capture of thermal neutron in the concrete sample. The prompt gamma ray yield was measured for 12 cm long concrete samples as a function of sample radius over a range of 6–11.5 cm radii. The optimum yield of the prompt gamma rays from the concrete sample was measured from a sample with 11.5 cm radius. The gamma ray yield was also calculated for 12 cm long concrete samples with 6–11.5 cm radius using Monte Carlo simulations. The experimental results were in excellent agreement with the calculated yield of the prompt gamma rays from the samples. Result of this study has shown the useful application of an accelerator-based PGNAA setup in elemental analysis of concrete sample. The facility can be further used to determine the chloride and sulfate concentrations in concrete samples for corrosion studies of reinforcement steel in concrete structures.

Validity test of design calculations of a PGNAA setup

A rectangular moderator has been designed for the prompt gamma ray neutron activation analysis (PGNAA) setup at King Fahd University of Petroleum and Minerals (KFUPM) to analyze Portland cement samples. The design of the moderator assembly was obtained using Monte Carlo calculations. The design calculations of the new rectangular moderator of the KFUPM PGNAA setup have been verified experimentally through prompt gamma ray yield measurement as a function of the front moderator thickness. In this study the yield of the 3.54 and 4.94 MeV prompt gamma rays from silicon in a soil sample was measured as a function of thickness of the front moderator of the rectangular moderator. The experimental results were compared with the results of the Monte Carlo simulations. A good agreement has been achieved between the experimental results and the results of the calculations. The experimental results have provided useful information about the PGNAA setup performance, neutron moderation, and gamma ray attenuation in the PGNAA sample.

Neutron moderation in a bulk sample and its effects on PGNAA setup geometry

In a prompt gamma ray neutron activation analysis (PGNAA) setup, the neutron moderation in the bulk sample also plays a key role. This can even dominate the thermalization effects of the external moderator in some cases. In order to study the neutron moderation effect in the bulk sample, moderators with two different sizes of the sample were tested at the King Fahd University of Petroleum & Minerals (KFUPM) PGNAA facility. In these tests, the thermal neutron relative intensity and prompt gamma ray yield from the two moderators were measured using nuclear track detectors (NTDs) and NaI detector, respectively. As predicted by Monte Carlo simulations, the measured intensity of thermal neutron inside the large sample cavity due to the external moderator was smaller than that from the smaller sample cavity. Due to its larger size, additional thermalization of neutrons will take place in the larger sample. In spite of smaller thermal neutron yield from the external moderator at the large sample location, higher yield of the prompt gamma ray was observed as compared to that from the smaller sample. This confirms the significance of neutron moderation effects in the bulk sample and can thereby affect the PGNAA geometry size. This allows larger samples in conjunction with smaller moderators in the PGNAA setup.

Prompt gamma ray analysis of Portland cement sample using keV neutrons with a Maxwellian energy spectrum—a Monte Carlo study

Monte Carlo calculations have been carried out to determine the prompt gamma ray yield from a Portland cement sample using keV neutrons from a 3H(p,n) reaction with a Maxwellian energy distribution with kT=52 keV. This work is a part of wider Monte Carlo studies being conducted at the King Fahd University of Petroleum and Minerals (KFUPM) in search of a more efficient neutron source for its D(d,n) reaction based (2.8 MeV neutrons) Prompt Gamma Ray Neutron Activation Analysis (PGNAA) facility. In this study a 3H(p,n) reaction based prompt gamma ray PGNAA setup was simulated. For comparison purposes, the diameter of a cylindrical external moderator of the 3H(p,n) reaction based PGNAA setup was assumed to be similar to the one used in the KFUPM PGNAA setup. The results of this study revealed that the optimum geometry of the 3H(p,n) reaction based setup is different from that of the KFUPM PGNAA facility. The performance of the 3H(p,n) reaction based setup is also better than that of the 2.8 MeV neutrons based KFUPM facility and its prompt gamma ray yield is about 60–70% higher than that from the 2.8 MeV neutrons based facility. This study has provided a theoretical base for experimental test of a 3H(p,n) reaction based setup.

Performance tests of external moderators of a PGNAA setup

Performance tests of external cylindrical moderators of an accelerator-based prompt gamma ray neutron activation analysis (PGNAA) setup have been carried out through thermal neutrons and prompt γ-ray yield measurements. The PGNAA setup is to be used for analysis of cement samples. This study was conducted to investigate the effects of geometry of cylindrical moderator on yield of thermal neutrons and prompt γ-rays for two different types of moderator assemblies. One of the moderators was to be used with a small sample and the other to be used with a large sample. Fast and thermal neutron yield was measured inside the sample volume as a function of the front moderator thickness as well as sample length. Neutron yield measurement was carried out at the King Fahd University of Petroleum and Minerals 350 keV pulsed beam accelerator using nuclear track detectors. The pulsed 200 keV deuteron beam with 5 ns pulse width and 31.25 kHz frequency was used to produce 2.8 MeV neutrons via D(d,n) reaction. Neutron yield measurements showed that the large sample moderator has a smaller yield of thermal neutrons as compared to the small sample moderator, which is in complete agreement with the results of Monte Carlo yield calculations of the thermal and fast neutrons from both the moderators. Finally, the prompt γ-ray yield from a Portland cement sample was measured using the two moderators and was compared with each other. As predicted by Monte Carlo simulations, in spite of a smaller yield of thermal neutrons, the large sample moderator has a higher yield of prompt γ-rays.

Monte Carlo simulations for design of the KFUPM PGNAA facility

Monte Carlo simulations were carried out to design a 2.8 MeV neutron-based prompt gamma ray neutron activation analysis (PGNAA) setup for elemental analysis of cement samples. The elemental analysis was carried out using prompt gamma rays produced through capture of thermal neutrons in sample nuclei. The basic design of the PGNAA setup consists of a cylindrical cement sample enclosed in a cylindrical high-density polyethylene moderator placed between a neutron source and a gamma ray detector. In these simulations the predominant geometrical parameters of the PGNAA setup were optimized, including moderator size, sample size and shielding of the detector. Using the results of the simulations, an experimental PGNAA setup was then fabricated at the 350 kV Accelerator Laboratory of this University. The design calculations were checked experimentally through thermal neutron flux measurements inside the PGNAA moderator. A test prompt gamma ray spectrum of the PGNAA setup was also acquired from a Portland cement sample, using a pulsed beam of 2.8 MeV neutrons. Prompt gamma ray peaks due to the calcium, silicon and iron content of the Portland cement were detected.

Monte Carlo Calculations for Design of An Accelerator Based PGNAA Facility

Monte Carlo calculations were carried out for design of a set up for Prompt Gamma Ray Neutron Activation Analysis (PGNAA) by 14 MeV neutrons to analyze cement raw material samples. The calculations were carried out using code the MCNP4B2. Various geometry parameters of the PGNAA experimental setup such as sample thickness, moderator geometry and detector shielding etc were optimized by maximizing the prompt gamma ray yield of different elements of sample material. Finally calibration curve of the PGNAA setup were generated for various concentrations of calcium in the material sample. Results of this simulation are presented.

Fast and thermal neutron intensity measurements at the KFUPM PGNAA setup

Fast and thermal neutron intensity distributions have been measured at an accelerator based prompt gamma ray neutron activation analysis (PGNAA) setup. The setup is built at the 350 keV accelerator laboratory of King Fahd University of Petroleum and Minerals (KFUPM). The setup is mainly designed to carry out PGNAA elemental analysis via thermal neutron capture. In this study relative intensity of fast and thermal neutrons was measured as a function of the PGNAA moderator assembly parameters using nuclear track detectors (NTDs). The relative intensity of the neutrons was measured inside the sample region as a function of front moderator thickness as well as sample length. Measurements were carried out at the KFUPM 350 keV accelerator using 2.8 MeV pulsed neutron beam from D(d,n) reaction. The pulsed deuteron beam with 5 ns pulse width and 30 kHz frequency was used to produce neutrons. Experimental results were compared with results of Monte Carlo design calculations of the PGNAA setup. A good agreement has been found between the experimental results and the calculations.