Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-10-07T17:21:58Z No. of bitstreams: 0 / Made available in DSpace on 2015-10-07T17:21:58Z (GMT). No. of bitstreams: 0 / O Brasil é o maior exportador e o segundo maior produtor de tabaco do mundo, de acordo com a safra de 2013/2014. A planta de tabaco (Nicotiana tabacum L.) é usada na fabricação de todos os derivados e a composição química do tabaco varia de acordo com o tipo de folha, como foram cultivadas, a região do plantio, as características da preparação (compressão, filtro e papel) e a variação de temperatura resultante da combustão incompleta do tabaco. Os derivados do tabaco são os produtos comercializados mais consumidos no mundo, como por exemplo, o cigarro, o charuto e o narguilé. Os efeitos danosos que estes produtos causam a saúde humana são há anos intensivamente discutidos e muitos estudos são realizados mundialmente relacionando o uso dos derivados do tabaco com diversas doenças. Existe pouca informação a respeito da caracterização radiológica da planta de tabaco na literatura internacional e nacional. O objetivo deste trabalho foi determinar a concentração dos radionuclídeos 238U, 234U, 230Th, 226Ra, 210Pb e 210Po, membros da série de decaimento do 238U, e os radionuclídeos 232Th e 228Ra membros da série de decaimento do 232Th nas variedades Burley e Virginia, as quais são as mais cultivadas no Brasil. Estes radionuclídeos naturais foram determinados em plantas adquiridas de produtores da região Sul do Brasil e também em plantas dessas mesmas variedades cultivadas em vasos com substrato orgânico e fertilizante com o objetivo de verificar prováveis influências dos fertilizantes e defensivos agrícolas usados pelos produtores na concentração dos radionuclídeos determinados. Os isótopos de U e Th, além do 210Po foram determinados por espectrometria alfa, após separação radioquímica e os radionuclídeos 226Ra, 228Ra e 210Pb pela medida alfa e beta total, também após separação radioquímica. Todas as partes da planta foram analisadas: raízes, caules e folhas, bem como os substratos orgânicos, fertilizantes e solos usados nos cultivos. Os isótopos de U e Th apresentaram resultados abaixo dos limites de detecção dos métodos para as folhas e caules de todas as plantas analisadas, apresentando resultados mensuráveis apenas nas raízes, solo e substrato. Os radionuclídeos 226Ra, 228Ra, 210Pb e 210Po foram determinados na grande maioria das partes das plantas, sendo os maiores valores obtidos para o 228Ra, o qual apresentou também o maior valor do fator de transferência. As plantas cultivadas no IPEN apresentaram valores inferiores de concentração dos radionuclídeos analisados quando comparados com as plantas cultivadas pelo produtor, pois estas foram cultivadas em potes com substrato orgânico e adição de fertilizante, cuja análise apresentou baixas concentrações dos radionuclídeos estudados. Baseados em dados da literatura nacional que estudou o fertilizante brasileiro, pode-se concluir, para as plantas do produtor, que o fertilizante exerce uma grande influência na concentração dos radionuclídeos estudados. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

In the analysis of environmental samples for uranium and thorium pollutants and at natural levels for the dating of geological samples there was felt a need to develop better uranium and thorium separation procedures to replace the established anion exchange method used at AEA Technology plc. This was the first aim of the PhD research. Separation of uranium from thorium prior to measurement of the isotopes by alpha spectrometry was necessary due to the similar alpha energies of234U and 230Th. TRU and UTEVA extraction chromatography resins (EIChroM Industries) were investigated as potential replacements to the anion exchange separation method. The resins are claimed by EIChroM to offer the advantage of providing an actinide specific separation while reducing the separation time from 2 to 0.5 days; the volume of acidic waste produced by a factor of 3, therefore, the cost of analysis was reduced. A uranium and thorium separation procedure using the UTEVA extraction chromatography resin was developed. The uranium and thorium were sorbed by the UTEVA resin from 2M nitric acid. The thorium was then eluted from the resin with 5M hydrochloric acid and the uranium with 0.02M hydrochloric acid. The separation procedure was then evaluated using uraninite ore, coral, granite and lake sediment reference materials. The uranium and thorium concentrations and the 234U/238U and 23oTh/234U activity ratio values determined for the reference material were in good agreement with certified values. The presence of plutonium was found to interfere with the measurement of uranium and thorium by alpha spectrometry. This was due to the similar alpha energies of uranium, thorium and plutonium. The co-elution of plutonium with uranium and thorium from the UTEVA resin was prevented by the inclusion of a reduction step using iron (Il) sulphamate. The resulting plutonium (Ill) was not retained by the UTEVA column. The chemical recoveries for the procedure were similar to those for anion-exchange, but the extraction chromatography procedure provided a more rapid separation using less reagents.

Light water reactors (LWRs) are the world’s dominant nuclear reactor system. Uranium (U)-fuelled LWRs produce long-lived transuranic (TRU) isotopes. TRUs can be recycled in LWRs or fast reactors. The thermal neutron spectrum in LWRs is less suitable for burning TRUs as this causes a build-up of TRU isotopes with low fission probability. This increases the fissile feed requirements, which tends to result in a positive void coefficient (VC) and hence the reactor is unsafe to operate. Use of reduced-moderation LWRs can improve TRU transmutation performance, but the VC is still severely limiting for these designs. Reduced-moderation pressurized water reactors (RMPWRs) and boiling water reactors (RBWRs) are considered in this study. Using thorium (Th) instead of U as the fertile fuel component can greatly improve the VC. However, Th-based transmutation is a much less developed technology than U-based transmutation. In this thesis, the feasibility and fuel cycle performance of full TRU recycle in Th-fuelled RMPWRs and RBWRs are evaluated. Neutronic performance is greatly improved by spatial separation of TRU and 233-6U, primarily implemented here using heterogeneous RMPWR and RBWR assembly designs. In a RMPWR, the water to fuel ratio must be reduced to around 50% of the normal value to allow full actinide recycle. If implemented by retrofitting an existing PWR, steady-state thermal-hydraulic constraints can still be satisfied. However, in a large break loss-of-coolant accident, the emergency core cooling system may not be able to provide water to the core quickly enough to prevent fuel cladding failure. A discharge burn-up of ~40 GWd/t is possible in RMPWRs. Reactivity control is a challenge due to the reduced worth of neutron absorbers in the hard neutron spectrum, and their detrimental effect on the VC, especially when diluted, as for soluble boron. Control rods are instead used to control the core. It appears possible to achieve adequate power peaking, shutdown margin and rod-ejection accident response. In RBWRs, it appears neutronically feasible to achieve very high burn-ups (~120 GWd/t) but the maximum achievable incineration rate is less than in RMPWRs. The reprocessing and fuel fabrication requirements of RBWRs are less than RMPWRs but more than fast reactors. A two-stage TRU burning cycle, where the first stage is Th-Pu MOX in a conventional PWR feeding a second stage continuous burn in a RBWR, is technically reasonable. It is possible to limit the core area to that of an ABWR with acceptable thermal-hydraulic performance. In this case, it appears that RBWRs are of similar cost to inert matrix incineration in LWRs, and lower cost than RMPWRs and Th- and U-based fast reactor recycle schemes.

Two aluminum spherical mirrors with radii of 203.2 mm and radii of curvature also of 203.2 mm have been used to construct a tunable Fabry-Perót type resonator operational at frequencies as low as 500 MHz. The resonator has been incorporated into a pulsed nozzle, Fourier transform, Balle-Flygare spectrometer. The spectrometer is of use in recording low J transitions of large asymmetric molecules where the spectra are often greatly simplified compared to higher frequency regions. The resonators use is illustrated by recording the rotational spectra of bromobenzene and iodobenzene. In related experiments, using similar equipment, the pure rotational spectra of four isotopomers of SrS and all three naturally occurring isotopomers of the actinide-containing compound thorium monoxide have been recorded between 6 and 26 GHz. The data have been thoroughly analyzed to produce information pertaining to bond lengths and electronic structures.

The efforts of my research have led to the successful construction of several instruments that have helped expand the field of microwave spectroscopy. The classic Balle-Flygare spectrometer has been modified to include two different sets of antenna to operate in the frequency ranges 6-18 GHz and 18-26 GHz, allowing it to function for a large range without having to break vacuum. This modified FTMW instrument houses two low noise amplifiers in the vacuum chamber to allow for the LNAs to be as close to the antenna as physically possible, improving sensitivity. A new innovative Balle-Flygare type spectrometer, the efficient low frequency FTMW, was conceived and built to operate at frequencies as low as 500 MHz through the use of highly curved mirrors. This is new for FTMW techniques that normally operate at 4 GHz or higher with only a few exceptions around 2 GHz. The chirped pulse FTMW spectrometer uses horn antennas to observe spectra that span 2 GHz versus the standard 1 MHz of a cavity technique. This instrument decreases the amount of time to obtain a large spectral region of relative correct intensity molecular transitions. A Nd:YAG laser ablation apparatus was attached to the classic Balle-Flygare and chirped pulse FTMW spectrometers. This allowed the study of heavy metal containing compounds. The instruments I constructed and the techniques I used have allowed the discovery of further insights into molecular chemistry. I have seen the effects of fluorinating an alkyl halide by determining the geometry of the carbon backbone of trans-1-iodoperfluoropropane and observing a ΔJ = 3 forbidden transition caused by a strong quadrupole coupling constant on this heavy molecule. The quadrupole coupling tensors of butyronitrile, a molecule observed in space, have been improved. The nuclear quadrupole coupling tensor of difluoroiodomethane was added to a list of variably fluorinated methyl halides upholding a trend for the magnitude of χzz. The study of SrS led to the determination of the Born-Oppenheimer breakdown terms and improving the precision of the SrS internuclear distance. I have also conducted the first pure rotational spectroscopic investigation on an actinide containing molecule, ThO.

Thorium is an element belonging to heavy metals, which is characterized by its radioactivity similarly to uranium and radon. Thorium is not commonly used in industry, but becouse of its radioactive properties it has a great potentional for future use in nuclear energetics. Thus, increasing release of Th into the soil, water and atmosphere can be expected in near future and through plant biomass it could become a part of food chains and webs and, thus, to represent a considerable health risks to humans. Studies devoted to research on thorium and its effects on plants has not been published much yet. The majority of these studies focus mainly only on plant abilities to accumulate thorium and/or monitoring distribution of thorium in plant body. But till now, a study is still missing, which would monitor the effect of thorium on the physiological characteristics of plants. Plants of Nicotiana glutinosa (L.) medium Thorium accumulatin were hydroponically cultivated Hoagland nutrient media differedin the presence of thorium, tartaric acid, putrescine and phosphates. In first part of the present study I monitored accumulation of thorium by tobacco plants under the influence of the above-mentioned modifications of media. In the second part, I studied the Th effect on the photosynthetic apparatus (contents...

In the leading part of this work I presented general information on the kingdom of fungi and fungal ecology focused on marofungi (macromycetes). Furthermore, I reviewed the phenomenon of trace elements accumulation in macrofungal fruit-bodies, particularly focused on uranium and its biogeochemistry. In the experimental part, results of my own research are presented. I determined concentrations of uranium, thorium, silver and lead by use of HR- ICP-MS and ENAA. The macrofungal samples were collected 1/ in clean areas with diverse geological bedrock, 2/ in uranium-polluted area in vicinity of Příbram (Central Bohemia, Czech Republic). Furthermore, selected trace elements were determined also in underlying soils by use of the both analytical methods. For investigation of trace elements mobility, the BCR sequential extraction was applied.

Philosophiae Doctor - PhD / Thoron Rn-220 is a radioactive gas with a half-life of 55.6 s. It has been identified as a possible health concern in specific places such as monazite processing plants and (rare-earth) mines. The short half-life of Rn-220 makes Rn-220 calibration sources and chambers less common than for the isotope Rn-222. There are many Rn-220 standard sources and chambers that are widely described in the literature and used for different applications and calibration. However, some of these chambers and sources are not easy to set up in typical nuclear environmental laboratories. In this project, we developed a Rn-220 standard source using a thorium nitrate solution (Th(NO3)4.6H2O). The solution was split into a large volume which was used in a Marinelli beaker to characterize its strength using a Hyper Pure Germanium (HPGe) detector, and a smaller volume of around 30 ml which was poured into a small bottle. The Rn-220 is extracted by bubbling air through the solution in the small bottle using an aerator. Gamma rays from the solution were measured simultaneously using a 76.2 mm × 76.2 mm NaI(Tl) detector. The gamma rays were measured for 66 hours. The accumulated spectra were thereafter analysed using an Excel spreadsheet where the counts in the Tl-208(2614 keV) peak were extracted and used to obtain the percentage of Rn-220 pumped out of the solution in the small bottle.

This work investigates the feasibility to perform an experiment at CERN n_TOF to study the fission cross section and fission fragment angular distribution (FFAD) of the 230Th(n,f) reaction. An analysis of fission fragment energy losses in the experimental target resulted in a choice of target thickness of 0.1 µm (100 µg/cm2 ), which yields good transmission out of the target at up to 45° emission angles from the target normal. A detection setup using ten PPAC detectors with nine thorium targets interleaved in between them was investigated, where the detectors and targets were tilted 45° with respect to the neutron beam. This makes it possible to measure all emission angles needed with respect to the neutron beam in order to determine the FFAD. For the experimental area EAR2 at n_TOF, a prediction of the count rate in the experiment resulted in low statistical uncertainties after a few weeks of beam time, which indicates that an experiment like this is feasible. / Detta projekt undersöker genomförbarheten av ett experiment vid CERN n_TOF för att mäta tvärsnittet och fördelningen av emissionsvinklar av fissionsfragment (FFAD) från 230Th(n,f)-reaktionen. En analys av energiförlusterna av fissionsfragment inuti torium-provet resulterade i en optimal provtjocklek på 0.1 µm (100 µg/cm2 ), vilket medför att fissionsfragment som emitteras i vinklar upp till 45° från provets normal har hög sannolikhet att transmitteras ut ur provet. En detektionsuppställning med tio PPAC-detektorer med nio toriumprov mellan dem undersöktes, där detektorerna och proven antogs vara snedställda med 45° från neutronstrålens riktning. Detta möjliggör detektion av fissionsfragment i alla vinklar som är nödvändiga för att kunna mäta hela FFAD. För experimentanläggningen EAR2 vid n_TOF, resulterade en uppskattning av antalet detekterade fissionsevent per sekund i låga mätosäkerheter efter ett par veckor av mättid, vilket antyder att experimentet är görbart.

Fuels comprised of the element thorium have become increasingly popular with researchers and the public as the next generation fuel due to its ability to produce its own fissile element (U-233) and generate lower concentrations of heavy actinides. The use of thorium can possibly lead to a self-sustaining cycle whereby the addition of fissile material is not required and that the fuel can breed sufficient amounts of U-233 for a continuous supply. Research into thorium use in CANDU reactors has mainly been focused on using driver elements such as U-235 or Pu-239 to initiate the nuclear reaction by taking advantage of bundle design or by mixing the thorium and driver fuel together; however, these methods have added complexities and may not lead to a pure thorium fuel cycle, but extend the life of current nuclear fuels used. This thesis will investigate a simpler means of utilizing thorium for the intent of breeding U-233 through the use of pure thorium bundles in a once-through cycle by the ways of a heterogeneous core loading in a CANDU-6 reactor model. A 3x3 multi-cell model using DRAGON 3.06K will simulate the dual fuel model by having the centre lattice enclosing the thorium bundle and the outer eight lattices enclosing the enriched uranium bundles as the driver fuel. Next, the diffusion code DONJON 3.02E is used to produce time-average, instantaneous, and initial startup full-core simulations. As well, a brief look at the refuelling operations on the thorium channels will be done. The presence of a thorium bundle places a negative reactivity load on the multi-cell, but causes a positive insertion of reactivity for a coolant void and shutdown scenario. In the full-core modelling, the final core configuration chosen shows that thorium channels should be located in the inner core rather than in the most outer channels to produce a flattening effect on the radial profile. Thorium channels will require a combination of SEU and thorium bundles in an attempt to maintain channel power levels. Specifically, the use of 4, 6, or 8 Th bundles were investigated. The most optimal core performance shown has a radial form factor of 0.816, a total average core burnup of 18.32 GWd/t, and operates within designed power limits. It is possible to implement pure thorium bundles into a reactor set in a dual fuel mode. A careful consideration of where thorium bundles should be located in the core can help flatten the radial power distribution and help the reactor operate within the operating licensing parameters without the use of adjuster rods while breeding U-233 for a future thorium fuel cycle. / Thesis / Master of Applied Science (MASc)