Radioactive Tracer Particle

For swarm-particle tracking, the tracer particles are simply the soda-lime glass beads in the bed. The glass beads contain 10% of sodium by weight, which can be converted to its radioactive isotope in a nuclear reactor. The Na24 isotope emits gamma radiation at 1.37 and 2.75 MeV, and has a half-life of 15 h. The irradiated activity of the 10-g glass particles was 400 mCi. 

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Radioactive particle tracking (RPT) can be used to map the velocity field by tracking the position of a single radioactive tracer particle in a reactor. The particle which may consist of a polypropylene shell contains a radionuclide that emits y-rays. 

The radiation detection process whereby the CAPTF detects radiation in a fluidized bed is schematically illustrated in Fig. 9.1. The radioactive tracer particle emits gamma photons at a certain average rate in all directions. These photons pass through the surrounding solid particles and the wall of the bed. Some of them reach the scintillation detector, which consists of a Nal crystal coupled with a photomultiplier. The interaction of the photon with the crystal produces fluorescent spikes that are picked up and amplified by the photomultiplier and converted into electrical pulses that are further amplified and counted by associated electronics. 

A computer-aided particle-tracking facility (CAPTF) has been developed to measure the motion of radioactive tracers in fluidized beds. This achievement was the first successful attempt to use the radioactive tracer technique to obtain detailed quantitative information on solids dynamic data in fluidized beds. The CAPTF makes use of one or more radioactive tracer particles that are dynamically identical to the bed particles under study. In... 

Since the initial introduction of laser diffraction instrumentation in the 1970s, many different applications to panicle si/e aniilysis have been reported. Ihese have included measurements of si/e distributions of radioactive tracer particles, ink particles used in photocopy machines, zirconia fibers, alumina particles, droplets from electronic fuel injectors, crystal growth particles, coal powders, cosmetics, soils, resins, pharmaceuticals, metal catalysts, electronic materials, phoiugraphic emulsions, organic pigments, and ceramics. About a dozen instrument companies now produce LALLS instruments. Some I.AI.LS instruments have become popular as detectors for size-exclusion chromatography. 

Lin W, Weinell C, Hansen P, Dam-Johansen K. Hydrodynamics of a commercial scale CFB boiler— study with radioactive tracer particles. Werther J, ed. Proc 6 Conf CFB. Wurzburg, Germany, 1999a,... 

Hydrogen as it occurs in nature is predominantly composed of atoms in which the nucleus is a single proton. In addition, terrestrial hydrogen contains about 0.0156% of deuterium atoms in which the nucleus also contains a neutron, and this is the reason for its variable atomic weight (p. 17). Addition of a second neutron induces instability and tritium is radioactive, emitting low-energy particles with a half-life of 12.33 y. Some characteristic properties of these 3 atoms are given in Table 3.1, and their implications for stable isotope studies, radioactive tracer studies, and nmr spectroscopy are obvious. 

Glaser and Lichtenstein (G3) measured the liquid residence-time distribution for cocurrent downward flow of gas and liquid in columns of -in., 2-in., and 1-ft diameter packed with porous or nonporous -pg-in. or -in. cylindrical packings. The fluid media were an aqueous calcium chloride solution and air in one series of experiments and kerosene and hydrogen in another. Pulses of radioactive tracer (carbon-12, phosphorous-32, or rubi-dium-86) were injected outside the column, and the effluent concentration measured by Geiger counter. Axial dispersion was characterized by variability (defined as the standard deviation of residence time divided by the average residence time), and corrections for end effects were included in the analysis. The experiments indicate no effect of bed diameter upon variability. For a packed bed of porous particles, variability was found to consist of three components (1) Variability due to bulk flow through the bed... 

Radioactive unstable atomic nuclei spontaneously emitting particles and energy Radioactive Tracer a radioactive substance used to monitor the movement and behavior of a chemical in biological processes and chemical reactions... 

In Section 3.1.1, self-diffusion was analyzed by studying the diffusion of radioactive tracer atoms, which were isotopes of the inert host atoms, thereby eliminating any chemical differences. Possible effects of a small difference between the masses of the two species were not considered. However, this difference has been found to have a small effect, which is known as the isotope effect. Differences in atomic masses result in differences of atomic vibrational frequencies, and as a result, the heavier isotope generally diffuses more slowly than the lighter. This effect can—if migration is approximated as a single-particle process—be predicted from the mass differences and Eq. 7.14. If mi and m2 are the atomic masses of two isotopes of the same component, Eqs. 7.13 and 7.52 predict the jump-rate ratio,... 

Several investigators have used radioactive tracer methods to determine diffusion rates. Bangham et al. (32) and Papahadjopoulos and Watkins (33) studied transport rates of radioactive Na+, K+, and Cl" from small particles or vesicles of lamellar liquid crystal to an aqueous solution in which the particles were dispersed. Liquid crystalline phases of several different phospholipids and phospholipid mixtures were used. Because of uncertainties regarding particle geometry and size distribution, diffusion coefficients could not be calculated. Information was obtained, however, showing that the transport rates of K+ and Cl" in a given liquid crystal could differ by as much as a factor of 100. Moreover, relative transport rates of K+ and Cl" were quite different for different phospholipids. The authors considered that ions had to diffuse across platelike micelles to reach the aqueous phase. 

Several tracers have been used in experiments describing axial mixing in fluidized beds of porous particles, e.g. acetone [37,57], Tryptophane [47], NaCl [49,56], radioactive tracers [58] and dextrane blue [59], It should be noted at this point, that measurement of RTD is not only important for determining possible domination of the chromatographic result by liquid mixing, Bo may as well be taken as a measure for the existence of a stable classified fluidized bed which is ready for sample application. Measurement of RTD in this case will provide a rational basis for the decision to start a large scale protein purification using a fluidized bed or to take measures for improvement of bed stability before application of valuable material. 

A widely used method to produce multiple-unit dosage forms has been the production of sachets that contain film-coated granules. More common is the use of capsules in which enteric-coated particles are filled. A study that used radioactive tracers revealed that enteric-coated erythromycin pellets in capsules were superior to enteric-coated tablets with respect to faster action of the drug caused by a shorter passage time of the coated granules in the stomach [49-51],... 

Detectable FDR is mostly particulate in nature. Unjacketed lead bullets produce residue in which greater than 70% of the particles are lead. Coated bullets give the same result, except that a substantial proportion of the lead particles contain copper from the coating material. With jacketed or semi-jacketed bullets the proportion of lead particles in the residue is greatly reduced. It was concluded that most of the lead in the residue comes from the bullet rather than from the primer. This has subsequently been confirmed by experiments involving the use of radioactive tracers.172... 

A tracer usually is a solution of a standardized radionuclide that is an isotope of the analyte radionuclide. With the identical chemical behavior of tracer and analyte, the yield of the tracer, determined radiometrically, represents the yield of the analyte. In this respect, the radioactive tracer has the same function as the stable carrier. Furthermore, for alpha particles of the usual 4-10 MeV energy in a thin source, the ratio of net count rate to activity is the same for the tracer and the analyte, so that the analyte activity is directly calculated from the activity of the tracer and ratio of the net count rates at the peaks of the analyte relative to the tracer, measured with an alpha-particle spectrometer. 

An isotopic radioactive tracer commonly is used for radionuclides that have no stable isotopes, notably for high-Z radionuclides that emit alpha particles. They also may be applied if a carrier is available as a more convenient way of determining the yield. A non-isotopic radionuclide can function as tracer for procedural steps in which it and the analyte react identically. 

Ostergaard and Michelsen104 measured the gas holdup in beds of 0.25-, 1-, and 6-mm glass particles using a radioactive tracer technique. They found that hG °c Uqg, where U0G is the superficial gas velocity, and n took values of 0.88, 0.78, and 0.93, respectively, for three particle sizes. The solid-free bubble-column gave n = 1.05. They also found that, in the solid-free system and in beds of 6-mm particles, the gas holdup decreased with increasing liquid flow rate whereas in beds of 0.25- and 1-mm particles, the gas holdup increased with increasing liquid flow rate. 

Catalyst-circulation rate was originally measured by use of wattmeters or torquemeters connected to the bucket-elevator system (175, 185). The energy required to drive the elevator motors was calibrated against catalyst-circulation rate, as calculated from average bucket loading and number of buckets transported per hour. Later a radioactive-tracer method was developed that involves introducing a few radioactive particles into the catalyst inventory and determining the time required for each of these particles to pass from one end of the reactor seal leg to... 

In section 4.5, the following designations are made Qi, Qij and qij are the mass flow rates of the particles stream (kg particles/sec) and Cj is the concentration of the tracer particles (kg tracer particles/kg particles). In such systems, the tracer particles are, usually, those of the original ones. They are, however, made radioactive or are painted, in order to distinguish them from the original particles. The latter makes it possible to determine their concentration versus time in the RTD experiments [73, p.l76], thus their mean residence time tm in the system. tm =... 

As for other constituents of the atmosphere, it is possible to set up a mass budget of the aerosol and to calculate its residence time. The main problem is to characterize the global distribution of particulate matter in order to determine its total mass in the troposphere. One may then apply the emission estimates of Table 7-11 to calculate the tropospheric residence time ta with the help of Eq. (4-11). This approach will be discussed in the first part of this section. Subsequently, we consider an independent method for estimating the residence time, which results from the use of radioactive tracers. Finally, the removal of aerosol particles by sedimentation and impactation at the Earth surface will be discussed. 

Changes in the concentration profile c(x, t) of dispersed particles within the diffusion cell can be studied by a variety of methods, including colorimetry (for colored substances), nefelometry, those involving the use of radioactive tracers, and others. 

Technetium (Tc Z = 43) is a synthetic element used as a radioactive tracer in medical studies. A Tc atom emits a beta particle (electron) with a kinetic energy (Ek) of 4.71 X10 J. What is the de Broglie wavelength of this electron (f =... 

The chapter begins with the fundamental measurements of resistance, capacitance, charge, and particle force. We proceed with flow measurements with various probes followed by a listing of some commercial electrostatic instruments. Nonelectrosatic measurements in multiphase flow such as the laser-Doppler anemometer, radioactive tracers, and stroboscopic techniques (Polaskowski, et. al, 1995 Soo, 1982) have not been discussed unless in relation to an electrostatic effect. 

Monitoring of solid/gas flow is important to safe and efficient operation of pneumatic transport that is used in many industrial processes such as coal mining and powder transport. Commonly employed techniques to measure particle velocity are a radioactive tracer method (Somerscales, 1981), optical techniques (Lee Srinivasan, 1978), electromagnetic methods (Bobis et al., 1986) and conventional mechanical approaches (Soo, 1990). 

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