Thickness measurement of material plates using low-activity sources with various energies in gamma-ray transmission technique.

This study proposes an approach based on the gamma-ray transmission technique to accurately determine the thickness of material plates using a low-activity source. For this purpose, we have set up an experimental configuration without collimators for both source and detector. Besides, a Monte Carlo simulation model using MCNP6 code has been created with the same geometric parameters as the empirical one. The calibration curves of thickness measurement were constructed for various energies of the incident gamma rays in the range of 123-661.7 keV and two materials of aluminum and copper using Monte Carlo simulation data. The thickness of the material plate was determined by applying experimental data to a known calibration curve. For a given material and gamma energy, the measurable thickness range (MTR) was estimated by investigating the dependence of the expected relative error on the thickness of the material plate. The obtained results show that the approach is feasible with the relative deviation between the measured and reference thicknesses of mostly less than 2% and the relative uncertainty of less than 3%. Such an approach could suggest a practical and cost-effective evaluation tool for optimizing the configuration to achieve a given accuracy corresponding to each type of material.

An approach based on gamma backscattering technique to measuring the density of liquid using the low-intensity radioactive source.

This work aims to develop a practical solution to measure the density of a liquid. Two purposes of this study: (1) using a low-activity source to measure the density of a liquid, and (2) simplifying the experimental arrangement to reduce the size and weight of the measuring system. The proposed solution is to develop a measurement technique without both detector and source collimators, while it considers an appropriate technique for analyzing the backscattering spectrum. To validate the proposed method, we used two groups of liquid: one group of liquids with a certified density and one group of liquids collected from the market. For the first group, the obtained results showed that the relative errors between the measured density and the reference one are below 6.8% and the uncertainties in density are below 4%, which confirms the feasibility of the proposed approach. For the second group, the liquids collected from the market include 70 percent alcohol, cooking oil, saltwater, fresh milk, diesel oil, dishwashing liquid, machine oil, and wine. The results obtained show that the relative errors between the densities determined by the proposed method and densities determined by the traditional method using density kit are less than 4.3%, the uncertainties in density when using the proposed method are below 3.2%. These results initially confirm that the proposed solution is completely applicable in measuring the density of a liquid.

A study on the sensitivity of the measurement of liquid density at different scattering angles using a gamma scattering technique.

This study aims to evaluate the sensitivity of the measurement of liquid density at different scattering angles using a gamma scattering technique. To perform this, the linear calibration curves of the ratio R (R is the ratio of the area under a single scattering peak for a liquid relative to that for water) versus the liquid density were constructed at different scattering angles. The sensitivity of the measurement is defined as the slope coefficient of these linear calibration curves. The results obtained from the Monte Carlo simulation data showed that the sensitivity of the measurement at different scattering angles including 70°, 80°, 90°, 100°, 110°, 120°, 130°, and 140° changes in the range from 0.44 to 0.48. Also, the results obtained from the experiment when performing the measurements at scattering angles of 90°, 100°, 110°, and 120° ranged from 0.46 to 0.48. This confirms that the dependence of the sensitivity of the measurement on scattering angle is insignificant. Besides, for every experimental dataset, we used each of 8 above-obtained calibration curves, in turn, to determine the densities of 8 liquids which yield the relative deviation between the measured density and the reference one is mostly less than 5%, the relative deviation of remaining cases (64 of 256 measurements) is in the range of 5.0%-9.9%.

An artificial neural network based approach for estimating the density of liquid applied in gamma transmission and gamma scattering techniques.

The study presents a new ANN-based approach to determine the density of a liquid applied in the gamma transmission and gamma scattering techniques. This approach used the Monte Carlo simulation combined with an artificial intelligence technique and experimental data to estimate the density of liquids. Two advantages of the proposed approach: (1) it is able to determine the density of a liquid by only measuring the gamma spectrum (transmission spectrum or scattering spectrum) without knowing the composition of the liquid, and (2) it is able to determine the density of a liquid when it is contained in a tube of various diameters. The artificial neural network model was trained by data obtained from simulation and then was used to predict the density of seven liquids with density in the range of 0.6 g cm-3 to 2.0 g cm-3 for the purpose of validating the proposed approach. For the gamma transmission technique, there are 25/28 samples with relative deviations between reference and predicted densities of less than 5%. The remaining three samples have deviations in the range from 5.2% to 6.3%. For the gamma scattering technique, there are 17/21 samples with a relative deviation of less than 5%. The remaining four samples have a deviation in the range from 5.2% to 6.9%. The results proved that the artificial intelligence technique combined with Monte Carlo based on gamma transmission and gamma scattering techniques is an effective approach for estimating the density of a liquid.

ANN coupled with Monte Carlo simulation for predicting the concentration of acids.

The present study proposes a new approach for determining the concentration of acids. The method is based on the combination of Monte Carlo simulation and artificial neural network (ANN) technique for predicting the concentration of acids. Firstly, a Monte Carlo simulation model is validated based on the comparison of simulation data with experimental data. Then, the whole data derived from the Monte Carlo simulation using the MCNP code was used to train the ANN model. The trained ANN model was used to predict the percentage concentrations of 14 acid samples, which yields the maximum relative deviation between the predicted and the reference concentrations is less than 3.5%.

Determining the density of liquid using gamma scattering method.

This study proposes an approach to determine the density of a liquid based on the gamma scattering method. The liquids used to determine density were poured in a cylindrical tube. This approach requires that the ratio R (the ratio of area under a single scattering peak for a liquid to that for water) increase linearly with an increase in the density of the liquid. In a certain range of density, a linear relationship was obtained between the ratio R and density, as described by a linear calibration curve with coefficients of slope and intercept, for the investigated tube diameters. In particular, the values of the slope and intercept could be expressed as mathematical functions of the diameter of the tube. For a given tube, the coefficients of slope and intercept of the linear calibration curve were obtained based on these functions, which helped determine the density of the liquid. The reliability of the proposed approach was evaluated by using it to calculate the densities of five liquids-n-hexane, diethyl ether, acetonitrile, toluene, and glycerol-using tubes with inner diameters of 1.8 cm, 2.25 cm, and 2.68 cm. The results show that the maximum relative deviation between the reference and the measured densities was 4.3%.

A revision of the virtual point detector model for calculating Nai(Tl) detector efficiency.

In present work, the validity of the virtual point detector (VPD) model for the NaI(Tl) detectors is studied and confirmed in the photon energy range of 60-1408 keV. The full energy peak efficiency (FEPE) of two NaI(Tl) detectors, which have scintillation crystal dimensions of 5.08 × 5.08 cm and 7.62 × 7.62 cm respectively, is measured for "point-like" radioactive sources on the symmetry axis with source-to-detector distances in the range of 2-40 cm. It is found that the VPD model is valid to fit too well to the experimental FEPE for the two surveyed NaI(Tl) detectors. The dependence of the VPD position on the incident photon energy for the NaI(Tl) detectors with different scintillation crystal dimensions is shown based on experimental data. A semi-empirical equation involving incident photon energy and source-to-detector distance is proposed to calculate the FEPE for the NaI(Tl) detectors. The calculated results for the two surveyed NaI(Tl) detectors by this equation are in a good agreement with experimental results for photon energies in the range of 344-1408 keV. However, the difference between experimental and calculated results is quite significant for source-to-detector close geometries for photon energies lower than 344 keV.

Semi-empirical method for determining the density of liquids using a NaI(Tl) scintillation detector.

In this study, we developed a new method for determining the density of liquids using the Compton backscattering technique. The principle of this method is based on the change in the area under a single scattering peak versus the liquid density. The linear calibration curve of the ratio R versus the density is required to determine the density of an unknown liquid (R is the ratio of the area under a single scattering peak for a liquid relative to that for water). In the proposed method, the calibration curve is completely constructed based on a simulation using the MCNP5 code. The method involves combining a simulation with an experiment as a semi-empirical method. Using this method, we determined the density of four liquids comprising acetonitrile, glycerol, nitric acid, and sulfuric acid, and the maximum deviations between the reference densities and measured values were less than 1.4%, except in the case of sulfuric acid, which was approximately 4.5%. The results obtained in this study strongly suggest that the proposed method is suitable and feasible for application.

Validation of gamma scanning method for optimizing NaI(Tl) detector model in Monte Carlo simulation.

The aim of this study is the validation of gamma scanning method for optimizing NaI(Tl) detector model in Monte Carlo simulation. The experimental procedure involved: scanning on front and lateral surfaces of the detector with collimated low-energy photon beam; calibrating the efficiency with energies between 31-1408 keV for point sources at distances of 0 cm and 30 cm from source to the detector. The Monte Carlo code used for the simulations was MCNP6. The diameter and the length of crystal were determined according to the measured results of gamma scanning with a collimated 241Am radioactive source. The distance from window to crystal was estimated using transmission measurement recorded on a second detector. The density of reflector was adjusted to obtain the match between measured and simulated values of efficiency ratio of 81 and 31 keV from a 133Ba radioactive source. The optimized model was applied in Monte Carlo simulations to determine the efficiency and energy spectrum response function of NaI(Tl) detector for point source measurements in two configurations. Good agreement was obtained between measured and simulated results.

Validation of an advanced analytical procedure applied to the measurement of environmental radioactivity.

In this work, an advanced analytical procedure was applied to calculate radioactivity in spiked water samples in a close geometry gamma spectroscopy. It included MCNP-CP code in order to calculate the coincidence summing correction factor (CSF). The CSF results were validated by a deterministic method using ETNA code for both p-type HPGe detectors. It showed that a good agreement for both codes. Finally, the validity of the developed procedure was confirmed by a proficiency test to calculate the activities of various radionuclides. The results of the radioactivity measurement with both detectors using the advanced analytical procedure were received the ''Accepted'' statuses following the proficiency test.

Estimating thickness of the inner dead-layer of n-type HPGe detector.

In this study, a procedure to estimate thickness of the inner dead-layer of an n-type coaxial HPGe detector is described. Experimental measurements are carried out with standard point sources: (54)Mn, (57)Co, (60)Co, (88)Y, (109)Cd, (134)Cs, (137)Cs, and (152)Eu at distances of 5 and 10cm from source to detector. Shape and dimensions of a high-purity germanium (HPGe) detector are determined by radiography to characterize the geometry accurately for Monte Carlo simulation. The role of thickness of the inner dead-layer on full energy peak efficiency is illustrated by MCNP5 code, and it is observed that slope coefficient of efficiency curve has a linear relationship with thickness of the dead-layer. The adjustment of dead-layer yields good agreement, with relative deviation of ≤3%, between experimental efficiency and simulated efficiency in the energy range of 88-1836keV.

Intercomparison NaI(Tl) and HPGe spectrometry to studies of natural radioactivity on geological samples.

In this study, in situ gamma spectra using NaI(Tl) detector have been compared with the laboratory measurements by using HPGe detector on geological samples. The results for measuring naturally occurring terrestrial gamma radiation of 40K and the decay series of 232Th and, 238U respectively of both detectors show a maximum deviation about 5%. The mass activities series from both detectors were checked for coherence using proficiency test procedure from the International Atomic Energy Agency. The reliability and precision pass for final scores for all the analytical determinations of are received "acceptable" for all radionuclides.

A prototype of radioactive waste drum monitor by non-destructive assays using gamma spectrometry.

In this work, segmented gamma scanning and the gamma emission tomography were used to locate unknown sources in a radioactive waste drum. The simulated detector response function and full energy peak efficiency are compared to corresponding experimental data and show about 5.3% difference for an energy ranging from 81keV to 1332.5keV for point sources. Computation of the corresponding activity is in good agreement with the true values.

Verification of Compton scattering spectrum of a 662keV photon beam scattered on a cylindrical steel target using MCNP5 code.

This article focuses on the possible application of a (137)Cs low-radioactive source (5mCi) and a NaI(Tl) detector for measuring the saturation thickness of solid cylindrical steel targets. In order to increase the reliability of the obtained experimental results and to verify the detector response function of Compton scattering spectrum, simulation using Monte Carlo N-particle (MCNP5) code is performed. The obtained results are in good agreement with the response functions of the simulation scattering and experimental scattering spectra. On the basis of such spectra, the saturation depth of a steel cylinder is determined by experiment and simulation at about 27mm using gamma energy of 662keV ((137)Cs) at a scattering angle of 120°. This study aims at measuring the diameter of solid cylindrical objects by gamma-scattering technique.