Thesis (M.S. in Physics)--Naval Postgraduate School, March 2010. / Thesis Advisor(s): Rodeback, G. W. "January 1962." Description based on title screen as viewed on June 2, 2010. DTIC Descriptor(s): Research Reactors, Hafnium, Half Life, Pneumatic Equipment, Measuring Instruments, Reactor Cores, Shielding, Detection, Gamma Emission, Computer Programming, Radioactive Isotopes, Radioactive Decay, Mixtures, Scintillation Counters, Isotopes, Least Squares Method. DTIC Identifier(s): AGN-201 Reactors, Fortran. Includes bibliographical references (p. 25). Also available in print.

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Lutetium oxide doped with europium (Lu2O3:Eu3+) has been established as a promising scintillator material with properties that are advantageous when compared to other scintillators such as cesium iodide doped with thallium (CsI:Tl). Due to high X-ray attenuation characteristics, Lu2O3:Eu3+ is an attractive material for use in high resolution digital X-ray imaging systems. However, challenges still remain especially in the area of light output for Lu2O3:Eu3+. Processing by physical vapor deposition (PVD) and manipulation of oxygen defect structure was explored in order to better understand the effect on the scintillation phenomena. PVD results were obtained using high temperature radio frequency sputtering (RF) and pulsed laser deposition (PLD) systems. Characterization of light output by radial noise power spectrum density measurements revealed that high temperature RF films were superior to those obtained using PLD. Optimization of sputtered films based on light output over a range of process parameters, namely temperature, power, pressure, and substrate orientation was investigated. Parameterization of deposition conditions revealed that: 75 watts, 10.00 mtorr, and 800°C were optimum conditions for Lu2O3:Eu3+ films. Manipulation of anionic defect structure in similar material systems has been shown to improve scintillation response. Similar methods for Lu2O3:Eu3+ were explored for hot pressed samples of Lu2O3:Eu3+; via controlled atmosphere annealing, and use of extrinsic co-doping with calcium. The controlled atmosphere experiments established the importance of oxygen defect structure within Lu2O3:Eu3+ and showed that fully oxidized samples were preferred for light output. The second method utilized co-doping by the addition of calcium which induced oxygen vacancies and by Frenkel equilibrium changed the oxygen interstitial population within the Lu2O3:Eu3+ structure. The addition of calcium was investigated and revealed that scintillation was improved with a maximum response occurring at 340ppm of calcium. PVD optimization and co-doping experimental results provided a template for the use of calcium co-doped Lu2O3:Eu3+ targets for deposition of films. Preliminary deposition results were promising and revealed that small additions (around 550 ppm) of calcium resulted in better activator efficiency. Calcium co-doped films have a predicted increase in the light yield greater than 14% when compared to analogous un-doped Lu2O3:Eu3+ films at 60keV.

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The main goal of this Thesis was to measure tritium activity in the Vltava River and in the vicinity of Temelín Nuclear Power Plant (hereinafter referred to as JETE) with the following objectives: Possibility to use the outlet of waste water damping unit (hereinafter referred to as VTOOV) as a control alerting system for nonstandard events in JETE, furthermore, monitoring of possible correlations between volume activity of tritium measured in VTOOV and activity above the limit value of the first quality class in selected sections of the Vltava River as well as comparison of the measured values with the results of other authors, and, finally, assessment of the relevance of the water quality estimated by the volume activity of tritium to the water quality according to other ingredients, i.e., stable isotopes of some metals and risk elements as well as general physical and chemical indicators. Theoretical part of the Thesis deals with radioactivity in general, activity of tritium, with regard to operation of nuclear plants, over the world and, especially, in the Czech Republic. The actual work consisted of collection of samples at predetermined places, preparation of these samples for measurement and measurement of tritium activity using scintillation spectrometer with liquid scintillator. Furthermore, basic chemical and physical properties of water, concentration of selected elements and also some anions were determined. The collected data were used for classification of waters from individual collection places into quality classes according to ČSN 75 7221. In all analyzed cases no activities were found which exceeded the limit values of liquid outlets from Temelín Nuclear Power Plant, given by regulations issued on waters by the District Health Office in Ceske Budejovice according to §8 of Act No. 138/73 Coll., in compliance with SÚJB requirements. This Thesis could be beneficial for possible utilization of VTOOV as a control alerting system for nonstandard events in JETE and also for assessment of impact of wastewaters from JETE on waters of the Vltava River.

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