Investigation of flow dynamics of molten glass in different solar glass production units using radiotracer method.

A radiotracer investigation was previously carried out to characterize the flow of the molten glass and to identify the cause of poor quality of the glass sheets produced in an industrial solar glass production unit (SGPU-1) (Pant et al., 2016). Based on the investigations, several flow abnormalities were identified and the design of the unit was modified to improve the quality of the product and meet the product specifications. Subsequently, the radiotracer investigation was repeated in the modified unit (SGPU-1m). The results of the study showed that the dead volume and homogenization time in the modified unit were significantly reduced with improvement in mixing of the molten glass as compared to the SGPU-1. Based on the results of the two investigations, a new glass production unit (SGPU-2) with enhanced capacity was designed, fabricated and commissioned. The radiotracer investigation was repeated in the newly designed unit with an objective to evaluate and validate its design. The results indicated that the performance of SGPU-2 was as per the design criteria and the quality of the glass sheets produced was as per the desired specifications.

Preparation and characterization of cobalt-60 glass microspheres for radioactive particle tracking applications.

The current work describes development and optimization of a process for preparation of cobalt-60 glass microspheres. These microspheres have potential for applications in radioactive particle tracking (RPT) studies in multiphase flow systems. In the first step of preparation, soda lime glass containing 5-10 wt% cobalt oxide was produced through melt-quench method. Subsequently, cobalt glass microspheres (CMSs) were prepared by microwave heating of tiny glass grains in presence of graphite. In the final step, radioactive cobalt-60 microspheres (RMSs) were produced by neutron irradiation of the CMSs in a nuclear reactor. The CMSs were characterized for surface morphology, elemental composition, homogeneity, crystalinity using SEM, EDX and XRD, respectively. The thermal behaviour of the microspheres was characterized by TG and DSC analysis. The size distribution of CMSs analyzed by SEM was found to be in the range 500-2000 µm. The preparation step was optimized to produce adequate activity in a single microsphere, so that they can be utilized for RPT applications.

Hydrodynamic modeling and radiotracer investigations in Kolkata Port Trust, Kolkata, West Bengal, India.

In this study, hydrodynamic modeling and radiotracer investigations were conducted in Kolkata Port Trust, Kolkata, West Bengal, India to investigate the dispersion of sediments and to evaluate the suitability of three different dumping sites (Upper Auckland, Lower Auckland and Eden) for dredged sediments along a navigation channel. Scandium-46 (148-240 GBq) comprising scandium glass powder with a particle size distribution ranging from 75-100 µm was used as a radiotracer. The radiotracer was injected onto the seabed at the selected site using a remotely operated injection system and its movement on the seabed was tracked over a period of three months using waterproof NaI(Tl) scintillation detector. The tracer concentration curves were plotted on a site map of the area for different trackings and isocount contours were plotted. Qualitative information was obtained from the isocount contours such as the general direction of movement and spread of the radiotracer. The isocount contours showed that the sediment predominantly moved away from the navigation channel. From the isocount, a transport diagram was plotted based on isocount counter and sediment transport parameters such as the general direction of movement by sediments on the seabed, transport velocity, transport thickness and bed load movement rate were determined for all the sites. The dispersion patterns obtained for the sediments by modeling were compared with the experimental results and they were found to be similar. Thus, the model results were validated and the proposed sites were found to be suitable for dumping the dredged material because the sediments did not return to the navigation channel.

Methods of preparation of microparticles for radioactive particle tracking experiments.

Radioactive particle tracking (RPT) technique is a relatively newer technique for the characterization of flow of process materials (liquids, solids) in laboratory- and pilot-scale industrial systems. The technique uses a single particle labelled with a suitable radioisotope having similar physical properties to that of the bulk of the process material. The preparation of a representative radioactive microparticle is a challenging task in the implementation of the technique. There are no standard methods available for the preparation of radioactive microparticles. This paper discusses some of the methods of preparation of radioactive microparticles for RPT studies. A few examples of RPT applications using the prepared microparticles are also discussed.

Investigation of flow dynamics of primary coolant in a delay tank of a swimming pool-type nuclear reactor using radiotracer technique.

Radiotracer investigations were carried out for tracing primary coolant in a delay tank of a swimming pool type nuclear reactor. The delay tank was designed to provide a certain delay or residence time to the primary coolant so that the short-lived radioisotopes such as (nitrogen-16 and oxygen-19) decay to a safer level before exiting from the delay tank. However, soon after commissioning of the reactor, the radiation levels at the exit of the reactor core and delay tank, in the working area were found to be higher than the permissible levels. Therefore, the main objectives of the investigations were to measure breakthrough and residence times and, to investigate flow dynamics of the coolant within the tank. Residence time distributions (RTDs) of the coolant were measured in the delay tank using technetium-99m as sodium pertechnatate as a radiotracer. The breakthrough time (BTT) and mean residence time (MRT) were determined from the measured RTD and the same were found to be inadequate to allow the decay of short-lived radioisotopes to the permissible levels. Axial dispersion model with two parallel flow streams was used to simulate the measured RTD curves. Results of the model simulation indicated bypassing of the coolant. Based on the results of the radiotracer investigations, necessary modifications were carried out in the design of the tank. After implementing the modifications, the radiotracer experiments were repeated and, the BTT and the MRT were found to increase sufficient enough to allow decay of the produced radioisotopes and thus to reduce the radiation levels at the exit of the delay tank and in the working area to the safer and permissible levels.

Experimental validation of design and performance parameters of radioactive particle tracking (RPT) experimentation.

In recent years, radioactive particle tracking (RPT) has emerged as a powerful noninvasive technique for characterization and visualization of flow in opaque multiphase flow reactors. This technique has been applied to a variety of multiphase flow reactors largely based on the theoretical framework for optimal design and performance parameters. No systematic evaluation and validation of the design and performance parameters of the RPT technique has been reported in the literature thus far. Consequently, the theoretical framework for the design of RPT experiments has had limited scalability and application to a wide variety of flow systems. Thus far, design of a "good" RPT experiment continues to be an art, no matter how much the richness of flow of information that the experimental method brings. The present work reports systematic experimental evaluation of design parameters for an optimal RPT experiment and validation of the theoretical results reported in literature. The experiments were performed in a carefully designed setup in which precise positioning of the tracer particle was made possible. The experiments assess the effect of various parameters on the performance of the RPT experiment, such as the choice of radioactive isotope, activity, gamma-ray energy, size of the detector, and relative positioning of detectors. Finally, a set of recommendations based on experimental work are provided to "optimally" perform the RPT experiment in any single or multiphase reactor.

Radiotracer investigation and modeling of an activated sludge system in a pulp and paper industry.

A radiotracer investigation was carried out in an activated sludge process (ASP) system of an effluent treatment plant in a pulp and paper industry. The system consists of an aeration tank and a secondary clarifier connected in series. The primary objective of the investigation was to measure mean hydraulic retention times (MHRTs) of wastewater and investigate the hydraulic performance of the ASP. Residence time distributions (RTD) of the wastewater were measured in an aeration tank and a secondary clarifier of the system using Iodine-131 as a radiotracer. The measured RTD data was treated and MHRTs were estimated. No bypassing was found to exist in the aeration tank and the secondary clarifier. However, the dead volume in the aeration tank and the secondary clarifier was found and estimated to be 2.34% and 4.6%, respectively. The treated curves were further simulated using suitable hydraulically representative mathematical models and detailed flow patterns in the aeration tank and the secondary clarifier were deciphered.

Study of adsorption characteristics of Au(III) onto coal particles and their application as radiotracer in a coal gasifier.

This paper describes a systematic study carried out to investigate adsorption characteristics of 198Au onto the surface of coal particles using a radiotracer technique. The main objective of the study was to optimize labeling conditions and utilize the labeled coal particles as a radiotracer for tracing coal particles in fluidized bed coal gasifiers. The effect of various experimental factors such as pH, amount of adsorbent, initial gold concentration, temperature and contact time between adsorbate and adsorbent were studied to obtain optimum conditions for maximum adsorption of 198Au on coal particles from an aqueous solution. Analysis of the data showed that the Langmuir model was found most suitable to describe the adsorption phenomena. The thermodynamic analysis showed that the adsorption process is feasible, spontaneous and endothermic in nature. The results of the kinetics suggested that the adsorption presumably follows second order kinetics and chemisorption in nature. Based on the optimized conditions, the amount of coal particles and activity to be used for tracing the coal phase in pilot-scale gasifiers was estimated. Accordingly, the radiotracer was prepared and successfully used for measurement of residence time distribution (RTD) in a pilot-scale coal gasifier.