Emissions of radionuclides to the atmosphere can lead to wet deposition on plants in theevent of rainfall. An increased level of radioactivity in the plants may occur due tointerception and retention of the radionuclides. If the content of the plants is above thethreshold limit value, entire yields may have to be destroyed. In order to preventcontamination or decrease the content countermeasures can be taken. The impact of thebiomass, leaf area index (LAI) and growth stage of the plant on the interception andretention is important to know in order to decide which countermeasures to use.Weather may also be an important factor. In this work the interception and retention of 134Cs and 85Sr by spring wheat, ley andspring oil-seed rape was studied. The impact of the biomass, LAI and growth stage ofthe plant and precipitation after deposition was also studied. The work was conducted asa field study with plots of the size 1 x 1 m. The plants were wet deposited with 134Cs and 85Sr by using a rain simulator. A total activity of 40 kBq/m2 for both radionuclideswas deposited on each plot. Depositions were performed during four different growthstages and the plants were sampled approximately four hours, one and five days afterdeposition. Activities of the dried plant samples were measured with a High PurityGermanium (HPGe) detector. Finally the interception fraction and the retention factorwere calculated. The study showed that the interception fraction was highest for the third growth stagefor both wheat and oil-seed rape; dough ripeness for wheat and ripening for oil-seedrape. Ley, which was harvested after two depositions, had the highest interceptionfraction at the second growth stage, flowering. Oil-seed rape and ley seemed to have aslightly higher interception fraction for 85Sr at all growth stages. There was a positiverelationship for the biomass and interception fraction, for the LAI and interceptionfraction the relationship wasn’t significant. The retention showed a weak trend ofdecreasing with time, with the decrease being largest during the first day after theinterception. However, the standard deviation was large and consequently the values uncertain. / Utsläpp av radionuklider till atmosfären kan genom regn leda till att de våtdeponeras påväxter. Radionukliderna kan då fångas upp av växterna och hållas kvar vilket kanresultera i förhöjda halter av radioaktivitet hos växterna. Om detta leder till attgränsvärden överskrids kan kassering av växter som används vid livsmedelsproduktionvara nödvändig. Motåtgärder kan vidtas för att undvika kontaminering eller minskahalterna. För att veta vilka motåtgärder som ska användas är det viktigt att veta hurväxtens biomassa, bladyteindex (LAI), utvecklingsstadium samt väderförhållandenpåverkar uppfångningen och kvarhållningen. I detta arbete undersöktes uppfångningen och kvarhållningen av 134Cs och 85Sr hosvårvete, vall och vårraps. Inverkan av växtens biomassa, LAI och utvecklingsstadiumsamt nederbörd efter deponering undersöktes också. Arbetet genomfördes som ettfältförsök med försöksrutor med storleken 1 x 1 m. Växterna våtdeponerades med 134Csoch 85Sr med hjälp av en regnsimulator. En total aktivitet på 40 kBq/m2 för bådaradionukliderna deponerades per försöksruta. Deponeringar skedde under fyra olikaväxtutvecklingsstadier och växtprover togs ungefär fyra timmar efter deponering samtett och fem dygn senare. Aktiviteten hos de torkade växtproverna mättes med en HighPurity Germanium (HPGe) detektor. Därefter beräknades uppfångningsfraktioner ochkvarhållningsfaktorer. Försöket visade att uppfångningsfraktionen var störst vid det tredjeväxtutvecklingsstadiet för både vete och raps; degmognad för vete och fröutveckling förraps. Vallen, som slogs av efter två deponeringar, uppvisade störst uppfångningsfraktionvid andra växtutvecklingsstadiet, blomning. Hos raps och vall verkadeuppfångningsfraktionen för 85Sr vara något högre vid samtliga växtutvecklingsstadier.För biomassan och uppfångningsfraktionen fanns ett positivt samband, för LAI ochuppfångningsfraktionen var sambandet inte signifikant. Kvarhållningen visade en svagtrend att minska med tiden, minskningen var störst under det första dygnet efteruppfångningen. Dock var standardavvikelsen stor och värden därmed osäkra.

Present day advanced technologies heavily rely on one particular class of matter, i.e. the crystals. It is the periodic nature of the atoms and the properties arising due to the periodicity in crystals that is exploited to meet various technological feats. The technological revolutions in the semiconductor, optics and communication industries are the examples. The anisotropy in the crystals gives them enhanced properties as required in the field of non-linear optics. The field of non-linear optics became practically a reality after the invention of lasers. The coherent and monochromatic optical beams in the visible and ultraviolet ranges are in high demand due to their application in the fields like material processing, semiconductor lithography, laser micromachining, laser spectroscopy, photochemical synthesis, inertial confinement fusion and other basic scientific studies. In this thesis, work on the growth and characterization of two technologically important non-linear optical crystals has been carried out after developing the necessary instrumentation and some novel techniques for synthesis and growth. Also, studies on the glassy nature of one of the crystals have been carried out. This thesis consists of seven chapters. The first chapter gives a brief introduction to the nonlinear optical phenomenon, crystal growth and glassy state. Instrumentation is the backbone of crystal research technology. Without precision growth equipments large size crystals cannot be grown and without precision characterization instrumentation no conclusion regarding the quality and usefulness of the grown material can be drawn. The work reported in Chapter 2 describes the instrumentation developed for the growth, processing and characterization of crystals grown by solution and melt growth techniques. In low temperature solution growth, crystal growth workstations have been developed using tanks (made of acrylic), heating elements, and stirring propellers. Cooling coils have been inserted into the designed water bath to grow crystals below ambient also. This bath has an advantage to work over a wide range of temperatures, so that maximum retrieval of the material is possible. The growth of large crystals is usually hindered due to spurious nucleation precipitating during the growth process. A novel nucleation-trap crystallizer has been designed and developed that facilitates the continuation of the growth run in spite of extra nucleation precipitating after seeding. In this crystallizer, the spurious nuclei and any other particles generated after the filtration are forced into a well, and the growth of spurious nuclei is arrested by manipulating the temperature of this trap. Achieving adequate heat flow and mass flow profiles is of vital importance for growing good quality crystals. An optimized stirring procedure for the solution or melt is needed for ensuring the desired supply of growth units to the crystal-nutrient interface, and for transporting away any debris of the crystal-growth process. An ACRT set up has been designed and developed. For the growth of crystals by the flux technique and from direct melt, a crystal puller has been designed and developed. The crystal puller consists of a crystal rotation unit, slow and fast pulling mechanisms and a control unit. The pulling assembly is protected from damage caused by possible human errors through interlock mechanisms. The vibration at the shaft of the seed rotation assembly has been minimized by using a dc motor for rotation. A versatile triangular / square wave oscillator has been designed for developing a dc motor control. By implementing this control, the speed of the motor does not vary with supply-voltage variations. A quarter-step switching logic sequence is introduced for stepper motors, which is used for the slow UP/DOWN movement of the puller. This puller can be controlled locally by a control panel provided with the puller, or through a PC remotely by bypassing the local control. Additionally, for the processing and characterization of the grown DKDP crystals, a closed-loop thread-cutter, a ferroelectric loop tracer, and a computer-controlled system for measuring the half-wave voltage have been developed. A novel mercury encapsulant seeding technique that facilitates the processing of solution with immersed seed is invented and has been described in Chapter 3. This technique allows processing of solution with the seed inside the growth chamber, and still avoids contamination of the solution and formation of crystal clusters that are normally generated when seed is inserted after processing of the solution. DKDP and KAP crystal seeds have been used to check the dissolution of seeds, if any, when immersed in pure water for several hours and at high temperatures after introducing the seal. It has been observed that the mercury seal does not allow creeping of water into the seed holder, and there is no dissolution of the seed. This technique has been practically implemented for the growth of crystals from aqueous solution and its usefulness has been demonstrated by growing ammonium acid phthalate, potassium acid phthalate and potassium di-deuterium phosphate crystals. Nonlinear-optical crystals find major use in inertial-confinement fusion (ICF) experiments. For such applications, nonlinear crystals with very large damage-resistance are needed. Alternatively, crystals with moderate damage resistance but large size can be used for frequency-conversion for efficient plasma experiments. Potassium di-hydrogen phosphate, KH2PO4 (KDP) and its deuterated analog, K(DxH1-x)2PO4 (DKDP) are at present the only nonlinear optical crystals which can be grown to large sizes and are suitable for ICF studies. Also, solid-state light valves, light deflectors, and laser communication devices require large and perfect tetragonal DKDP crystals, with high deuterium concentration for easier operation. Chapter 4 describes the growth and characterization of DKDP crystals. DKDP crystals have been grown by all the three techniques i.e. conventional, platform and novel mercury encapsulant seeding techniques. Details about a new approach for the synthesis of DKDP solution have been given. A comparative study of the grown crystals by mercury-encapsulant technique and other techniques is described. Habit modification was observed due to the placement of seed crystals at an off-centre position and orientation in mercury encapsulant seeding technique and has been discussed. The grown crystals have been characterized for homogeneity, dislocations, transmission, DSC, rockng curve, etc. Due to the higher photon energies and the ability to be more tightly focused, coherent radiations of shorter wavelength (deep-UV) are in demand. The photon energies in this region are sufficient for bond-breaking processes in many materials, and find applications in fields like material processing, semiconductor lithography, laser micromachining, laser spectroscopy, photochemical synthesis, etc. Although excimer lasers (XeCl, KrF, ArF etc.) produce significant power in the deep-UV region, these laser systems involve corrosive gases, and are bulky, apart from requiring regular maintenance. A maintenance-free, compact, solid-state laser is preferable. But this, in turn, requires an efficient NLO crystal in that region. CLBO is one such crystal. Growth of CLBO crystals has been carried out by the flux-growth technique using B2O3-deficient flux, as well as from stoichiometric melt and has been discussed in Chapter 5. It was observed that the nucleation of material on platinum wire or spontaneous nucleation was difficult to achieve in spite of high supercooling. After forcing cracks into the mass deposited on platinum wire nucleation could be achieved. The growth of crystals was carried out on seeds with different orientations. Transmission studies, etch-pit studies and harmonic-generation experiments were performed on the grown crystals. The glass-forming tendency of CLBO has been studied and reported in Chapter 6. DTA experiments show that CLBO melt generally transforms to glass on cooling. Even at a cooling rate as low as 1°C/min, the material does not crystallize but transforms into glass. Ergodicity making and glass transition temperatures were determined for glassy CLBO. Since neither the crystallization peak nor the melting peak was observed in DTA experiments during the heating part of thermal cycle for glassy CLBO, a new approach of seeded crystallization was adopted in the calorimetric experiments to achieve crystallization. Since the size of added nuclei is already above the critical radius, the onset of crystallization peaks is independent of the critical-radius energy barrier. Kissenger method was applied to determine the activation energy of seeded- crystallization process. The transformation of glass CLBO to the crystalline phase is mediated by dendrites. Possibility of bulk crystal growth from the glassy state has been discussed, and a novel idea of surface crystallization is proposed. Chapter 7 summarizes the work carried out and projects the scope for future work.

No description available.

It was being exploratored radiation pollution of fish living in water-cooling basin of Ignalina Nuclear Power Plant (NPP) in master's work. The objectives of work. NPP water-cooling basin's fish. The purpose of work was to estimate fish (Rutilus rutilus ( L.), Abramis brama ( L.), Esox lucius ( L.) and Perca fluviatilis ( L.)) contamination degree with macrobiotic radioisotopes cesium ( 137Cs) and strontium ( 90Sr) of Ignalina Nuclear Power Plant ( NPP) water cooling basin, to point up estimated radio-pollution concentrations dependence from fish capturing period of year, their (fish) varietal particularity, nutritional mode of fish life and compare with fish contamination by macrobiotic radioisotopes in other Lithuanian waters. Methods of work. Gama spectral analysis to estimate 137Cs levels in foodstaffs; 90Sr method estimation in foodstaffs and environmental samples by method of Tcherenkov radiation. The experiment was accomplished in the Laboratory of Environmental Protection – the subdivision of Ignalina NPP in 2004-2005. Samples of fish were delivered for the investigations by three times a year ( by 20 kg for every time (month); by 5 kg of different kind; totally 60 kg). It was being applied that method for statistical evaluation of secured data - calculable marks evaluation of secured results. All findings are on 95 % reliability level. The results of investigations showed, that larger specific activity of ( 137Cs) has been found in Esox lucius ( L.) and Perca... [to full text]

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A Penning-type surface-plasma negative hydrogen (H^-) ion source has been delivering beam at the ISIS pulsed spallation neutron and muon facility for over thirty years. It is one of the most powerful and well-renowned H^- sources in the world. Although long-term experience has allowed the source to be operated reliably and set up in a repeatable way, it is treated as something of a 'black box': the detailed plasma physics of why it works has always been unclear. A vacuum Vessel for Extraction and Source Plasma Analyses (VESPA) has been developed to understand the ISIS ion source plasma and improve the beam extracted from it. The VESPA ion source is operated in a completely new regime whereby the analysing sector dipole magnet housed inside a refrigerated 'cold box', presently used on ISIS, is replaced by an on-axis extraction system. The new extraction system incorporates a novel einzel lens with an elliptical aperture. This is the first demonstration of an elliptical einzel being used to focus an asymmetric H^- ion beam. With the dipole magnet removed, the ion source has been shown to produce 85 mA of H^- beam current at normal settings; of which 80 mA is transported through the new einzel lens system, with a normalised RMS emittance of 0.2 π mm mrad. Optical emission spectroscopy measurements have shown a plasma density of 10¹⁹ m^–3, an H₂ dissociation rate of 70%, an almost constant electron temperature of 3.5 eV and an atomic temperature which linearly increases above the electron temperature. In support of these principal measurements, rigorous particle tracking, electrostatic and thermal simulations were performed. In addition, a suite of new equipment was manufactured by the author. This includes a fast pressure gauge, a temperature controller, a high voltage einzel lens circuit, a fast beam chopper and a caesium detection system.

The Chernobyl nuclear disaster of April 26, 1986 is the worst nuclear accident in the history of mankind. An experiment conducted in the 4th reactor resulted in its explosion and a huge amount of radionuclides escaped into the environment in the course of the subsequent fire. The greater part of Europe was contaminated by radioactive fallout, including the former Czechoslovak Socialist Republic. From a health point of view, the most harmful radioactive substances causing radioactive contamination were caesium 137Cs and iodine 131I. The then government did not provide objective and true information to the citizens and the media depicted the disaster as an insignificant incident. I set the following goals of my thesis: a) to develop an overview of immediate and especially long-term consequences of the accident; b) to analyse the knowledge of the population of the South Bohemian Region of the consequences of the Chernobyl disaster depending on the age of respondents. For fulfilling the set goals, I set myself the following hypotheses: H1) the theoretical division of the population's knowledge will be normal; H2) the knowledge of persons over 45 years of age will statistically be significantly higher than that of younger people. I handled the given theme using available specialized literature, Internet sources and publications published by relevant institutions. In the introductory part I describe the construction of the power plant, basic technical parameters of the reactor used and the course and causes of the actual accident. The next section is focused on the consequences of the accident in individual time periods immediately, after 10 years and after 20 years. I devote myself both to influences on human lives and health and to environmental, social, economic and psychological consequences. Furthermore,I describe the situation in former Czechoslovakia and the way of informing the population by the then government. The last section of the theoretical part is dedicated to the present situation in the Chernobyl region and at the power plant itself. While compiling the research part of the thesis, I gathered data among the inhabitants of the South Bohemian Region through questionnaire investigation. I addressed a total of 280 respondents, of which 140 were under 45 years of age and 140 were over 45 years of age. The questionnaire contained 15 questions concerning basic, not professional knowledge in this area. For the purposes of my questionnaire investigation, I divided the South Bohemian Region into districts. The selection of individual towns within the framework of the questionnaire investigation was carried out at random, by drawing lots. 280 questionnaires were completed in all, of which 140 questionnaires were completed by respondents under 45 and 140 questionnaires were completed by respondents over 45. By drawing lots, I selected 100 questionnaires out of these completed questionnaires, each age group being included. The test of the set hypotheses and statistical evaluation are carried out using descriptive and mathematical statistics. I carried out statistical evaluation by testing normality, using X2-good agreement test. I mutually compared the knowledge of the groups monitored by testing using a two-sample t-test, based on the estimate of empirical parameters from each group. Based on statistical investigation I came to the conclusion that the division of the population's theoretical knowledge was normal, which confirms the first hypothesis. The results of the investigation also unambiguously confirmed the fact that the knowledge of the population over 45 years of age was statistically significantly higher than the knowledge of the younger group of respondents. As far as total evaluation is concerned, the average value of correct answers in case of the older group of respondents reached 71%, while the younger group showed just 44% of correct answers, which confirms the second se hypothesis.

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