Intercomparison of gamma ray scattering and transmission techniques for fluid–fluid and fluid–air interface levels detection and density measurements

Gamma radiation detector selection for CT scanner

Three types of gamma radiation detectors associated with distributed electronics namely, NaI (Tl), HPGe and LaBr3(Ce) are compared primarily focusing on electronic noise and scattering noise. Additionally, detectors of same make, material, size and electronics are also compared. A methodology is proposed to select the most suitable detector for computed tomography (CT) among the available options. Standard deviation parameter is employed to estimate electronic noise without performing CT experiment. Kanpur theorem-1(KT-1) is used to estimate the scattering noise quantitatively after verifying its sensitivity to scattering noise. The impact of scattering noise on CT profiles is evaluated using dice similarity dice coefficient. A good resemblance between KT-1 and dice coefficient is observed. A maximum difference of 56% in scattering noise is observed when five detectors used simultaneously instead of single detector whereas a discrepancy of 85% is observed between different types of radiation detectors. As far as ease of handling, operational and capital cost is concern one has to compromise minimum 12% of accuracy in CT reconstruction if NaI (Tl) detector is used with respect to best alternative available. The proposed methodology can be applied to measurement that require minimal scattering interference data other than CT experiments. The manufacturer can add noise level of detector as a characteristic parameter in the data sheet.

Comparison of MCNPX and FLUKA Monte Carlo codes in the simulating a nuclear gauge

In this paper, a nuclear gauge was simulated using MCNPX and FLUKA codes. This device consists of a fluid-containing vessel, three BC400 rod plastic scintillator and a⁶⁰Co gamma source. Simulation studies show that the changes in the count of each of the three detectors and the sum of their counts decrease with increasing vessel water height. The simulation results were compared with the measurement results. Comparison results show that the mean count difference between MCNPX code and experimental results is about 3% lower than FLUKA code, but the computation time using FLUKA code is approximately 2.8 times less than the MCNPX code.

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%.

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.

Impact of focused gamma ray beam angle on the response of density logging tool

The response of the gamma-gamma density logging tool with different focused gamma ray beam angle is investigated by using the MCNP code. This work focuses on the four aspects of spatial distribution and energy spectrum of scattered gamma rays, measurement uncertainty, the depth of investigation, and vertical resolution of the logging tool. The results show that the density measurement accuracy can be improved when a relative larger collimator angle is employed, and the vertical resolution of the tool would not get worse.

A novel method of combined detector model for gamma-ray densitometer: Theoretical calculation and MCNP4C simulation

This study focuses on investigating a new model of combined backscatter and transmission method for nuclear densitometer. In this method for density measurement, a true combination of transmission and backscatter methods was studied and related equations were developed. The MCNP4C code was used for simulation of this combined detector model (CDM) and by applying theoretical calculations, density equation was corrected for the proposed nuclear densitometer. In the new method presented here, the buildup effect was estimated by an online system that was improved in our laboratory and was replaced by a new conceptual calculation. Hence, for the purpose of buildup reduction, there was no need for the shield around the detector, as it was monitored and reduced online. Furthermore, this study showed that the RSQ function could be improved by the CDM. The measurement technique proposed in this study has a better linearity trend than the transmission technique. Thus, the ability of CDM to improve the accuracy of the nuclear densitometer was shown.

A new automated and precise calibration method for gamma level gauges with rod detector arrangement

Gamma-ray liquid level gauging is of particular importance in several industries. Industrial vessels, tanks, and reactors, which work at high temperatures and pressures, usually have thick metal walls up to 20cm. These factors make it impossible to know the exact level of liquid or fluid while the system is operating. For this reason, the calibration process of the gamma level gauges is difficult as it is impossible to gain access to the inside of the vessels, which is important during the calibration process. In this study, a new auto-calibration method was proposed for the aforementioned situations.

Gamma photon techniques for detection of nucleation in superheated emulsion detectors for neutron dosimetry

Application of transmission and scattering gamma photon techniques for calibration of superheated emulsion detectors used for neutron dosimetry is described. The bubbles nucleated in the detector due to neutron exposure generate detectable changes in both attenuation and scattering properties of the medium, and the magnitude of change in properties depends on population density of bubbles nucleated and in turn is proportional to neutron dose. The experimental set-up consists of (137)Cs and (241)Am sources and an HPGe detector-based gamma-ray spectrometer. An indigenously developed bubble detector and a commercially available one (BTI, Canada) are used in the present study. Theoretical models for the variation in transmitted and scattered intensities through the bubble detector as a function of neutron dose are formulated, and the experimental results obtained are found to be in good agreement with the models. In the neutron dose region studied, the transmission technique shows better sensitivity than scattering technique.

An improved Compton scattering method for determination of concentration of solutions

An improved Compton scattering method for determination of concentration of low-Z solutions is presented. The Monte Carlo (MC) numerical simulation of the scattering phenomena is done using the MCNP code. A unique non-linear extrapolation method is followed in correcting the scattered intensity for self-absorption and multiple scattering. The density ratios obtained using non linear extrapolated scattered intensity values are free from self-absorption and multiple scattering and agree well with the standard ones within experimental errors. The sensitivity study of transmission and scattering methods for determination of concentration of solutions having closer attenuation parameters at 661.6 keV is carried out to predict the range of effectiveness and suitability of these methods. The slopes (sensitivity/unit concentration) of the curves obtained from scattering method are higher by a factor of 1.26 compared to those of the transmission method in the measured range of concentrations.