Prompt Gamma Neutron Activation Analysis Setup Research Articles

Moderation and shielding optimization for a 252Cf based prompt gamma neutron activation analyzer system

Prompt Gamma Neutron Activation Analysis (PGNAA) is a fast, online and the non-destructive elemental analysis method which is widely used in industries such as cement and coal. In the present study, optimization of the moderator and gamma radiation shield of a 252Cf neutron source in a PGNAA setup, utilizing Monte Carlo simulation is succeed. The objective is to enhance the thermal neutron spectrum and minimize potential gamma rays. The results show 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 options for the intended purpose. As a result of this optimization, increased efficiency of the PGNAA setup through (nth,γ) reaction and elevated prompt gamma flux which provides higher accuracy for the detector system.

A new Am–Be PGNAA setup for element determination in aqueous solution

A new prompt-gamma neutron activation analysis (PGNAA) setup has been designed for element determination in aqueous solution with a 300 mCi 241Am–Be neutron source and a 4in.×3in. (diameter×height) BGO detector, uncooled. A polyethylene cylindrical sample container approximately 40cm in outer radius and 80cm in height was used. To reduce the neutron dose in the detector, a block of 5cm thickness Li2CO3 was placed between the source and the detector for separation, but no gamma-blocker was used. By adjusting the position of the detector and optimizing the geometrical conditions of the setup, the element detection limit with a low activity neutron source was further improved. This methodology was checked by simulations with chlorine, mercury and cadmium determination and by experiments with chlorine determination in aqueous samples. The results show a good linear relationship between chlorine concentration and the count of its characteristic peak, and the detection limit of chlorine can reach 41.7mg/L with a collection time of 3600s for each spectrum. Additionally, a linear relationship was identified between mercury concentration and the count of its characteristic peak, but for cadmium, a non-linear relationship was observed in the simulations.

Optimization of PGNAA set-up for the elements detection in aqueous solution

A prompt gamma neutron activation analysis (PGNAA) set-up was developed for the elements detection in aqueous solution, which includes a 241Am-Be neutron source and a 4-inch BGO detector. The geometry of set-up is determined by a series of simulations with the MOCA code to improve the efficiency of the elements detection. The thermal neutron flux and the gammaray self-absorption are considered during the optimization calculations. Experiments were performed to validate the set-up using samples including chlorine and mercury, respectively. The result shows that the characteristic peak count has linear relationship with the chlorine and mercury concentration changing. The minimum detectable concentrations of chlorine and mercury were found as 54 mg/L and 51.4 mg/L, respectively.

Detection efficiency of low levels of boron and cadmium with a LaBr 3:Ce scintillation detector

The response of a cylindrical 3 in.×3 in. (height×diameter) LaBr 3:Ce detector was measured for low energy prompt gamma-rays from boron and cadmium contaminated water samples using a newly designed portable neutron generator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup. Prompt gamma-rays were measured from water samples contaminated with 0.031, 0.125, 0.250 and 0.5 wt% boron and 0.0625, 0.125, 0.250 and 0.500 wt% cadmium. The experimental yield of boron and cadmium prompt gamma-rays measured with the LaBr 3:Ce detector based PGNAA setup were compared with the results of Monte Carlo calculations. An excellent agreement between the experimental and calculated yields of 478 keV gamma-ray from boron and 558 keV gamma-rays from cadmium from boron and cadmium contaminated water samples, indicate an excellent response of the LaBr 3:Ce detector for the low energy prompt gamma-rays.

Non-destructive analysis of concrete for corrosion studies using nuclear technique

Chloride-induced reinforcement corrosion is the principal cause of deterioration of concrete structures in the Arabian Gulf and the world over. Preventive measures against corrosion require maintaining the chloride and sulphate concentration in concrete below the threshold limits specified by the standards. This requires monitoring the chloride and sulphate concentration in concrete, and a nondestructive technique is preferable for this purpose. The Prompt-Gamma Neutron Activation Analysis (PGNAA) technique can be used to monitor the concentration of corrosive elements in concrete specimens. An accelerator-based PGNAA setup has been developed to measure the chloride and sulphate concentration in concrete. The PGNAA technique has been utilised successfully to measure the elemental composition of concrete. In this regard, several studies were undertaken to determine the calcium, silicon, chloride and sulphate concentration in the concrete specimens. Furthermore, the concentration of compounds, such as lime and silica was also determined. The results of these studies along with a description of the facility are presented in this paper.

Characterization of an Am–Be PGNAA set-up developed for in situ liquid analysis: Application to domestic waste water and industrial liquid effluents analysis

A prompt gamma neutron activation analysis (PGNAA) set-up with an Am–Be source developed for in situ analysis of liquid samples is described. The linearity of its response was tested for chlorine and cadmium dissolved in water. Prompt gamma efficiency of the system has been determined experimentally using prompt gamma of chlorine dissolved in water and detection limits for different elements have been derived for domestic waste water. A methodology to analyze any kind of liquid is then proposed. This methodology consists mainly on using standards with water as bulk or in the case of absolute method, to use gamma efficiency determined with prompt gammas emitted by chlorine dissolved in water. To take into account the thermal neutron flux variations inside the samples, flux monitoring was carried out using a He-3 neutron detector placed at the external sample container surface. Finally, to correct for the differences in gamma attenuation, average gamma attenuations factors were calculated using MCNP5 code. This method was then checked successfully by determining cadmium in industrial phosphoric acid and our result was in good agreement with that obtained with inductively coupled plasma (ICP) method.

Monte Carlo optimization of sample dimensions of an 241Am–Be source-based PGNAA setup for water rejects analysis

The present paper describes the optimization of sample dimensions of a 241Am–Be neutron source-based Prompt gamma neutron activation analysis (PGNAA) setup devoted for in situ environmental water rejects analysis. The optimal dimensions have been achieved following extensive Monte Carlo neutron flux calculations using MCNP5 computer code. A validation process has been performed for the proposed preliminary setup with measurements of thermal neutron flux by activation technique of indium foils, bare and with cadmium covered sheet. Sensitive calculations were subsequently performed to simulate real conditions of in situ analysis by determining thermal neutron flux perturbations in samples according to chlorine and organic matter concentrations changes. The desired optimal sample dimensions were finally achieved once established constraints regarding neutron damage to semi-conductor gamma detector, pulse pile-up, dead time and radiation hazards were fully met.

Performance improvement of a PGNAA setup due to change in moderator design: A Monte Carlo study

Effect of neutron source-moderator geometry has been studied on the performance of a thermal neutron capture-based prompt gamma neutron activation analysis (PGNAA) setup. In the study prompt gamma-ray and thermal neutron yield was calculated for various positions of the neutron source inside 3–10 cm long high density polyethylene moderators. The study has been carried out for a Portland cement sample using Monte Carlo calculations. The maximum yields of the thermal neutrons and prompt gamma-rays have been observed for a neutron source at a distance of 1 cm from the sample. The maximum yield of the 1.94 and 6.42 MeV prompt gamma-ray from a Portland cement sample has been observed for moderators having length equal to or greater than 7 cm. The yield of both gamma rays is 2.57 times higher than the previously reported value for a PGNAA setup with the source placed outside a 5 cm thick moderator. The higher yield of gamma rays will result in higher sensitivity of the PGNAA setup.

Gamma-ray yield dependence on bulk density and moisture content of a sample of a PGNAA setup: A Monte Carlo study

Monte Carlo calculations were carried out to study the dependence of γ-ray yield on the bulk density and moisture content of a sample in a thermal-neutron capture-based prompt gamma neutron activation analysis (PGNAA) setup. The results of the study showed a strong dependence of the γ-ray yield upon the sample bulk density. An order of magnitude increase in yield of 1.94 and 6.42 MeV prompt γ-rays from calcium in a Portland cement sample was observed for a corresponding order of magnitude increase in the sample bulk density. On the contrary the γ-ray yield has a weak dependence on sample moisture content and an increase of only 20% in yield of 1.94 and 6.42 MeV prompt γ-rays from calcium in the Portland cement sample was observed for an order of magnitude increase in the moisture content of the Portland cement sample. A similar effect of moisture content has been observed on the yield of 1.167 MeV prompt γ-rays from chlorine contaminants in Portland cement samples. For an order of magnitude increase in the moisture content of the sample, a 7 to 12% increase in the yield of the 1.167 MeV chlorine γ-ray was observed for the Portland cement samples containing 1 to 5 wt.% chlorine contaminants. This study has shown that effects of sample moisture content on prompt γ-ray yield from constituents of a Portland cement sample are insignificant in a thermal-neutrons capture-based PGNAA setup.

Interferences in Prompt γ Analysis of corrosive contaminants in concrete

An accelerator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup has been developed to measure the concentration of corrosive chloride and sulfate contaminants in concrete. The Minimum Detectable Concentration (MDC) limit of chlorine and sulfur in the concrete depends upon the γ-ray used for elemental analysis. For more interfering γ-rays, the MDC limit is higher than that for less interfering γ-rays. The MDC limit of sulfur in concrete measured for the KFUPM PGNAA setup was calculated to be 0.60±0.19 wt%. The MDC limit is equal to the upper limit of sulfur concentration in concrete set by the British Standards. The MDC limit of chlorine in concrete for the KFUPM PGNAA setup, which was calculated for less interfering 1.165 MeV γ-rays, was found to be 0.075±0.025 wt%. The lower limits of the MDC of chlorine in concrete was 73% higher than the limit set by American Concrete Institute. The limit of the MDC can be improved to the desired standard by increasing the intensity of neutron source. For moreinterfering 5.715 and 6.110 MeV chlorine γ-rays the MDC limit was found to be 2–3 times larger than that of 1.165 MeV γ-rays. When normalized to the same intensity of the neutron source, the MDC limits of chlorine and sulfur in concrete from the KFUPM PGNAA setup are better than MDC limits of chlorine in concrete obtained with the 241Am–Be source-based PGNAA setup. This study has shown that an accelerator-based PGNAA setup can be used in chlorine and sulfur analysis of concrete samples.

Measurement of lime/silica ratio in concrete using PGNAA technique

Prompt gamma neutron activation analysis (PGNAA) technique has been used to determine lime/silica ratio in concrete samples using an accelerator-based PGNAA facility. The ratio was determined from the measured yield of 6.42 MeV prompt γ-rays of calcium and 4.93 MeV γ-rays of silicon from the six concrete samples. The experimental results were compared with the results of the Monte Carlo simulations. An excellent agreement has been achieved between the two. The study has demonstrated successful use of the accelerator-based PGNAA setup in non-destructive analysis of the concrete samples.

Prompt gamma analysis of chlorine in concrete for corrosion study

Measurement of chlorine in concrete is very important for studying of corrosion of reinforcing steel in concrete. Corrosion of reinforcing steel is primarily ascribed to the penetration of chloride ions to the steel surface. Preventive measures for avoiding concrete structure reinforcement corrosion requires monitoring the chloride ion concentration in concrete so that its concentration does not exceed a threshold limit to initiate reinforcement concrete corrosion. An accelerator based prompt gamma neutron activation analysis (PGNAA) setup has been developed for non-destructive analysis of elemental composition of concrete samples. The setup has been used to measure chlorine concentration in concrete samples over a 1–3 wt% concentration range. Although a strong interference has been observed between the chlorine γ-rays and calcium γ-rays from concrete, the chlorine concentration in concrete samples has been successfully measured using the 1.164 and 7.643 MeV chlorine γ-rays. The experimental data were compared with the results of the Monte Carlo simulations. An excellent agreement has been achieved between the experimental data and results of Monte Carlo simulations. The study has demonstrated the successful use of the accelerator-based PGNAA setup in non-destructive analysis of chlorine in concrete samples.

Corrosion Study of Concrete Using PGNAA Technique

Monitoring of elemental composition of structural concrete is required to protect reinforcing steel in concrete against corrosion. Prompt Gamma Neutron Activation Analysis (PGNAA) technique has been used to measure the elemental composition of concrete samples. In this study 2.8 MeV neutron-based PGNAA setup at King Fahd University of Petroleum and Minerals (KFUPM) has been tested for elemental analysis of concrete sample. Later the setup will be used to measure chloride and sulfate ion concentration in concrete samples. Corrosion of reinforcing steel in concrete is believed to be caused by chloride and sulfate ions. In the KFUPM PGNAA facility the prompt gamma rays are produced through capture of thermal neutrons in bulk sample. The sample size, to be used with PGNAA setup, is determined through Monte Carlo simulations. In this study, prompt gamma ray yield from calcium and silicon present in the concrete sample was measured for various thickness of the front moderator of the PGNAA setup. The experimental yield of prompt gamma ray was compared with the results of the Monte Carlo simulations and an excellent agreement has been achieved between the two. The study has shown that the PGNAA technique can be successfully applied for elemental analysis of the concrete samples

Performance comparison of an241Am-Be neutron source-based PGNAA setup with the KFUPM PGNAA setup

Monte Carlo calculations have been carried out to compare the performance of an 241Am-Be neutron source-based prompt gamma neutron activation analysis (PGNAA) setup with that of the 2.8 MeV neutron-based PGNAA setup at King Fahd University of Petroleum and Minerals (KFUPM) to analyze Portland cement samples. This work is a part of a wide Monte Carlo studies being conducted at KFUPM in search of a more efficient neutron source for its 2.8 MeV neutrons, from the D(d,n) reaction, based PGNAA facility. In this study an 241Am-Be neutron source-based PGNAA setup was simulated. For comparison, the diameter of a cylindrical external moderator of the 241Am-Be neutron source, based PGNAA setup, was assumed to be similar to that used in the KFUPM PGNAA setup. The results of this study revealed that although the optimum geometry of the 241Am-Be neutron source-based setup is similar to that of the KFUPM PGNAA facility, the performance of the 241Am-Be neutron source-based setup is slightly poorer than that of the 2.8 MeV neutron-based setup.