ABSTRACT EXCHANGES OF STRONTIUM ON CLINOPTILOLITE ZEOLITE G&Uuml / L, &Ouml / zkan MS, Department of Chemical Engineering Supervisor: Prof. Dr. Hayrettin Y&uuml / cel November 2003, 110 Pages Sr-90 and Cs-137, nuclear fission products, are the major sources of medium-level radioactive waste which must be decontaminated. Inorganic ion exchangers are the preferred materials to eliminate radioisotopes from aqueous nuclear waste because of their high selectivity, radiation and thermal stability, low cost and likely compatibility with cement containment. Clinoptilolite and other zeolites are widely used in nuclear industry for the removal of radioisotopes from aqueous nuclear waste. In this study, the performance of local clinoptilolite zeolite from G&ouml / rdes region has been investigated so as to determine the conditions under which it can be used effectively in the column for strontium and cesium removal. It was found that under different loading conditions, breakthrough capacity varied from 0 to 0.4078 meq/g for strontium removal, breakthrough capacity varied from 0.1178 to 0.7800 meq/g for cesium removal. It was also determined that the increase of the flow rate reduced the exchange capacity of the bed. Effect of cationic form of the zeolite (Na-CLI: Sodium form of clinoptilolite and Original-CLI: Original form of clinoptilolite) on the breakthrough capacity was also searched. It was observed that Na-CLI performed much better for the removal of strontium and cesium with respect to its original form. In addition, effect of presence of calcium in the feed solution on the breakthrough capacity was investigated and it was found that presence of calcium in the feed solution makes strontium removal essentially impossible, in the case of cesium, presence of calcium in the feed solution decreases breakthrough capacity significantly.

This paper treats a non-intrusive method of measuring electric fields in plasmas and other sensitive or hostile environments. The method is based on the use of an atomic hydrogen beam prepared in the metastable fine structure quantum state 2s1/2. Interaction with the field that is to be measured causes Stark mixing with the closely lying 2p1/2, whose spontaneous decay rate is much higher than that of 2s1/2. As a result, the total transition rate to the ground state and consequently the intensity of the Lyman-α line (121.6nm) is increased. Observations of emitted radiation from a region in which the interaction takes place are used to draw conclusions about the electric field, effectively providing a way to measure it. In the first section, the theory behind the method is described, using time dependent perturbation theory and taking into account both Lamb shift and hyperfine structure. A description of the set-up that we have used to test the theoretical predictions follows and practical aspects related to the operation of the experiment are briefly addressed. Measurements of the dependence of the Lyman-α intensity on both electric field frequency and amplitude are presented and shown to be in agreement with theory. These measurements have been performed in vacuum and in an argon plasma, both for static and RF fields. Two mechanisms, labeled oscillatory and geometrical saturation, that decrease the emitted intensity for strong fields are identified and described, and both are of importance for the future implementation of the studied diagnostic in a fusion device or other plasma experiment. Studies of the field profiles between a pair of electrically polarized plates have been carried out and algorithms for relating measured data to actual values of electric field strength have been developed. For static fields in vacuum, collected data is compensated for geometrical saturation and the resulting profiles are compared to those calculated with a finite element method. Good correspondence is seen in many cases, and where it is not, the discrepancies are explained. Static profile measurements in a plasma show the formation of a sheath whose thickness has been studied while varying discharge current, pressure and plasma frequency. The qualitative dependence of the sheath thickness on these parameters is in accordance with well established theory. When it comes to RF fields, a possible standing wave pattern is detected in the plasma despite problems with low signal to noise ratio. In order to optimize the working conditions of the set-up, effects of charge accumulation due to ions present in the hydrogen beam have been studied as well as errors due to residual particle fluxes during the off-phase when pulsing the beam. A conceptual design suggestion for implementing the method in the edge plasma of a tokamak or another similar device, based on the collected information, is also given.

The Morse/Long Range (MLR) potential has become one of the most reliable and highly used potential energy functions for diatomic molecules. It includes the theoretical long range behaviour that diatomic molecules are known to exhibit as they approach the dissociation limit. Heavy alkali metals with adjacent electronic states often exhibit strong coupling between the spin and orbital angular momentum. The ground state X¹Σg⁺ and the lowest lying triplet state aᶟΣᵤ⁺ of Cs₂ exhibit such coupling effects and as a result, modeling the highest vibrational states of these states is a non-trivial problem. Utilizing scattering length values obtained from published analysis of 60 Feshbach resonances, the correct form of the potential energy function was determined. Moreover, the scattering length values were used to determine the correct leading dispersion coefficient that describes the true form of the long-range potential energy functions. All previous attempts to determine global potential energy functions for these states have considered only the optical spectroscopic data. This is the first ever effort attempting to use scattering lengths determined from cold atom collision experiments in a combined analysis with conventional spectroscopic data.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 224-236).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 173-183).

For thin epitaxial metal films, when the thickness is on the order of the Fermi wavelength, [lambda subscript F], quantum confinement can dramatically alter the physical properties of the film. These so-called Quantum Size Effects (QSE) can dramatically alter the morphology of thin films by an intricate interplay between kinetics and surface energy driven thermodynamics. These effects lead to rich growth-related phenomena in Pb(111) films grown on semiconductor substrates such as Si(111). For example, QSE can drive flat film formation when growth is dominated by surface energy oscillations. This is rather surprising for Pb/Si systems because of a rather high lattice mismatch. However, these films are not defect free, but rather show common occurrences of three defect types. Low Temperature Scanning Tunneling Microscopy (LT-STM) was utilized to characterize these defects on the atomic scale. Furthermore, these defects create modulations in the electron density resulting in fluctuations in QWS near defect sites. Another topic of recent interest is how QSE affect adsorption of as well as how adsorbates modify QSE for these Pb films. In this thesis, LT-STM and first principles calculations were utilized to study Cs adsorbates on Pb film surfaces, defects, and step edges. Cs adsorption is intricately related to the electronic structure of the surface, especially the defect sites which can act as surface traps. These Cs adsorbates, which are assumed to be ionized, enhance elastic surface scattering of empty-state electrons. This results in observable wave interference patterns near Cs impurities. Furthermore, Cs adsorbates, by an overall step energy reduction, can promote QSE-related nanostructures, which are otherwise too weak when kinetic effects cannot be ignored. This enhancement of "quantum stability" is driven by favorable Cs step binding and can be explained within the contexts of Density Functional Theory (DFT). / text

The Morse/Long Range (MLR) potential has become one of the most reliable and highly used potential energy functions for diatomic molecules. It includes the theoretical long range behaviour that diatomic molecules are known to exhibit as they approach the dissociation limit. Heavy alkali metals with adjacent electronic states often exhibit strong coupling between the spin and orbital angular momentum. The ground state X¹Σg⁺ and the lowest lying triplet state aᶟΣᵤ⁺ of Cs₂ exhibit such coupling effects and as a result, modeling the highest vibrational states of these states is a non-trivial problem. Utilizing scattering length values obtained from published analysis of 60 Feshbach resonances, the correct form of the potential energy function was determined. Moreover, the scattering length values were used to determine the correct leading dispersion coefficient that describes the true form of the long-range potential energy functions. All previous attempts to determine global potential energy functions for these states have considered only the optical spectroscopic data. This is the first ever effort attempting to use scattering lengths determined from cold atom collision experiments in a combined analysis with conventional spectroscopic data.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 5 uppsatser.

Thesis (Ph. D., Chemical Engineering)--University of Idaho, May 2006. / Major professor: Vivek Utgikar. Includes bibliographical references (leaves 99-107). Also available online (PDF file) by subscription or by purchasing the individual file.

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