دکتر محسن شریف زاده

Using a dredger to remove mud and garbage accumulated in the river or sea docks is a common and important process. In order to monitor the condition of sediments on the sea bed, it is necessary to use an online measurement system for the concentration of transfer slurry from the floor to the surface. The nuclear-based systems have this important and operational capability to provide the possibility of online monitoring of the passing slurry by installing it on the pipeline without causing any disruption in the transfer process. The concentration measurement system of the cutter-suction dredger uses the combination of two nuclear and non-nuclear parts to measure the fluid parameters desired by the client, such as the volumetric and mass flow rate of the two-phase fluid and its components. In using hybrid systems for this purpose, basic conditions such as online measurement capability, non-physical, chemical or environmental interference in the passing flow, compatibility with the operational conditions of temperature, pressure, humidity and vibrations in the dredging site, measurement accuracy should be met and safety principles should be considered. In this study, using Monte Carlo simulation with MCNPX code, the effect of different geometrical and dimensional parameters of output gamma ray collimator on the accuracy of measuring the concentration of passing slurry was investigated, and with the considerations related to personnel radiation safety, the final optimal mode was proposed. The decrease in the placement depth of the horizontal spring inside the beam is associated with the simultaneous maximum of gradient and count statistics. In all of the mentioned situations, the opening of the conical beam-forming aperture has a higher sensitivity and resolution compared to a rectangular one.

Pigging is one of the conventional processes in the oil and gas industries, which is done in order to remove sediments from pipelines and also perform some non-destructive tests. On the other hand, due to various branches in the main pipeline, there is a possibility of stopping the pig. The right solution is to use mesh caps that not only prevent the pig from getting stuck, but also guarantee the passage of flow through all the main and secondary lines. According to the opinions of technical inspectors, there is no comprehensive information about the presence/absence of these caps in a large number of branches. The industrial radiography lacks the ability to detect the presence and absence of the cap in a fully filled pipe due to the average energy of the emitted beam and its geometrical structure. It is focused on the conceptual design of the nuclear system for investigating the possibility of pigging in the location of pipeline branches in the Monte Carlo environment. Ultimately, the results show the fact that in the situation where the source and the detector are perpendicular to the axis of the main and secondary branches and facing each other, the maximum counting sensitivity and discrimination can be achieved. Moreover, the relative difference of two states with and without the presence of metal grid for two states of filling the pipe with air and oil is equal to 53.8% and 57.1%, respectively.

In this paper, by using Monte Carlo simulation of MCNPX software, the design and optimization of the dimensions and distances between the plastic scintillation detectors used in the gamma ray portal monitor in order to build based on these optimized dimensions It can be. The test and performance evaluation steps of the gamma ray portal monitor based on the radiation acceptance test section of the International Electrotechnical Commission standard No. IEC 62244:2024 including the false alarm test, the background effects test (on the performance of the detectors), the gamma radiation detection test and the out-of-range response test is accepted. The results of the conducted evaluation tests confirm the compliance of this portal monitor with the IEC 62244 standard. Based on this, it can be concluded that the design, simulation and placement of the detectors have been done with sufficient accuracy and are approved. Also, the minimum detectable activity of the device for the 60Co source was equal to 0.7 microcurie activity and for the 137Cs source equal to 1.5 microcurie activity at 1 meter with a discrimination level of ±2.7σ, which is comparable to the available commercial monitors.

One of the important steps in the nuclear fuel cycle is uranium enrichment. It is essential to carry out control processes using continuous measurement on the way to uranium with the desired enrichment of the facility. On the other hand, due to being in the environment with high external radiation and also suitable for internal exposure of the operator, especially when working with uranium powder, it is necessary to use accurate instruments with the ability to monitor online and continuously, which is a special place in the nuclear instrumentation. In this work, we decided to work on a conceptual design of the enrichment and weight measurement system for uranium tetrafluoride powder into loading and handling tanks in the nuclear industry. For this purpose, with the aim of reducing costs while eliminating maximum counting error, focus on reading only gamma rays emitted from powder or with radioactive lateral source was considered. The design was based on geometric location optimization of scintillating detector/detectors around the tank containing uranium tetrafluoride powder in order to have maximum accuracy in measurement. The simulation results in Monte Carlo software show that for different enrichment percentages and also different heights of uranium powder inside the cylindrical tank, we are able to have maximum accuracy in measuring two parameters of richness percentage and powder weight at specific angles.

In the process of extracting gas and condensate from the seabed, we often encounter a multiphase flow. Multiphase fluid flow to pass through the transmission pipes requires the separation of outgoing water from the formation on offshore platforms in order to eliminate corrosion effects in downstream facilities such as refinery. Formation water often enters the sea after separation. Water monitoring of the formation in terms of salinity is an important part of the process of measuring the volumetric rate of multiphase flow components at the separator site by single-phase metering systems. Considering the high dependence of parameters such as density, viscosity and electrical conductivity of fluid to salinity level, we decided to investigate the possibility of conceptual design of formation water salinity system based on gamma technique. The change in the key characteristics related to the gamma beam shaping module emitted from the cobalt-60 radioactive source and with the consideration of radiation safety of personnel, it was obtained the optimum geometric and dimensional conditions of the collimator in order to achieve maximum accuracy in different amounts of salinity fraction of sodium iodide salt in water measurement.

When there is limitation access to one side of the structure in industry, one of the best methods for thickness measurements is the Compton scattering. In this paper, due to the statistical behavior of dispersed beam counting, we discuss the accuracy of the measurement for steel thickness. Using the experimental method and comparing it with MCNP simulation code, the accuracy is obtained less than 0.2 mm.