<p>Predmet istraživanja doktorske disertacije je konstruisanje,izgradnja<br />i uvođenje u rutinski rad, kao i naučna istraživanja detektorskog<br />sistema, kome će kao osnova poslužiti&nbsp; 9``x 9`` NaI(Tl) spektrometar<br />oblika jame. Pomenuti detektorski sistem će zbog veličine aktivne<br />zapremine kao i njenog specifičnog oblika (oblika jame) posedovati<br />najveću efikasnost detekcije u poređenju sa svim&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />gamaspektrometrijskim sistemima trenutno u upotrebi u Laboratoriji<br />za nuklearnu fiziku, Prirodno-matematičkog fakulteta, Univerziteta u<br />Novom Sadu i &scaron;ire. Gamaspektroskopija je nedestruktivan metod<br />koji se može primeniti za određivanje niskih aktivnosti uzoraka bez<br />prethodne hemijske pripreme i predstavlja zlatni standard u<br />radioekolo&scaron;kim istraživanjima,kontroli životne sredine itd.<br />Detektorski sistem velike efikasnosti koji je tokom izrade doktorata<br />166 pu&scaron;ten u rad, omogućuje značnu redukciju vremena merenja kao i<br />sniženje minimalnih detektabilnih aktivnosti. Na ovaj način je&nbsp;&nbsp;&nbsp;&nbsp; Laboratorija za nuklearnu fiziku dobila detekcioni sistem pomoću kojeg je moguće vr&scaron;iti analizu uzoraka niske aktivnosti u naučne svrhe kao i za rutinsku kontrolu uzoraka iz životne sredine.<br />Za upotrebu&nbsp; 9``x 9`` NaI(Tl)&nbsp; spektrometra oblika jame u rutinskim<br />merenjima radiolo&scaron;ke kontrole uzoraka niskih aktivnosti, izvr&scaron;ena je<br />neophodna adekvatna kalibracija efikasnosti detektorskog sistema i<br />to na razne oblike matrica uzorakai na taj način su rezultati merenja<br />načinjeni uporedivim sa akreditovanim poluprovodničkim sistemima<br />Laboratorije za nuklearnu fiziku.</p> / <p>Subject&nbsp; of&nbsp; doctoral dissertation&nbsp; research&nbsp; is&nbsp; the design,&nbsp; construction&nbsp;and&nbsp; implementation&nbsp; in&nbsp; routine work,&nbsp; as well as scientific&nbsp; research&nbsp; of&nbsp;detector system,&nbsp; as the basis&nbsp; on well-type&nbsp; 9``x&nbsp; 9``&nbsp; NaI&nbsp; (Tl)&nbsp;spectrometer. The aforementioned&nbsp; detector system, due to&nbsp; the size&nbsp;of&nbsp; the active&nbsp; volume&nbsp; as well as&nbsp; its specific&nbsp; form (well)&nbsp; possess&nbsp; the&nbsp;highest&nbsp; detection efficiency&nbsp; compared&nbsp; with all gammaspectrometric&nbsp;systems&nbsp; currently&nbsp; in use&nbsp; at the Laboratory of&nbsp; Nuclear Physics,&nbsp;Faculty of Science,&nbsp; University of Novi&nbsp; Sad and&nbsp; beyond. Gammaspectroscopy is a non-destructive method that can be applied for the determination&nbsp; of low&nbsp; activity&nbsp; samples&nbsp; without&nbsp; chemical preparation&nbsp; and&nbsp; is the gold&nbsp; standard&nbsp; in&nbsp; radioecological&nbsp; studies, environmental control and so on.</p><p>The detector systems&nbsp; high&nbsp; efficiency, which was&nbsp; during the&nbsp;preparation of&nbsp; doctoral dissertation&nbsp; put into operation,&nbsp; allows&nbsp;significant&nbsp; reduction in&nbsp; measurement time&nbsp; as well as&nbsp; lowering&nbsp; the&nbsp;minimum&nbsp; detectable&nbsp; activity.&nbsp; In this way,&nbsp; the&nbsp; Laboratory&nbsp; for Nuclear&nbsp;Physics&nbsp; get&nbsp; detection system&nbsp; which can be used&nbsp; for the analysis&nbsp; of&nbsp;samples&nbsp; of low activity&nbsp; for scientific purposes&nbsp; as well as&nbsp; for&nbsp; routine&nbsp;control of environmental samples.</p><p>For use&nbsp; well type&nbsp; 9``x&nbsp; 9``&nbsp; NaI&nbsp; (Tl)&nbsp; spectrometer&nbsp; in routine&nbsp;measurements&nbsp; of &nbsp;radiological samples&nbsp; of low&nbsp; activity, there was a&nbsp;need&nbsp; adequate&nbsp; calibration of&nbsp; the detector&nbsp; efficiency&nbsp; of the system&nbsp;with&nbsp; various&nbsp; forms of&nbsp; sample&nbsp; matrix&nbsp; thus&nbsp; the results of&nbsp;measurements&nbsp; made&nbsp; comparable&nbsp; with accredited&nbsp; semiconductor&nbsp;<br />systems in Laboratory for Nuclear physics.</p>

When an accident involving the possibility of a plutonium contaminated wound occurs, the contamination is often quantified using sodium iodide (NaI(Tl)) and high purity germanium (HPGe) detection systems. The NaI(Tl) system is used to quantify the amount of contamination, while HPGe is used to gauge the depth of contamination in the wound. Assessment of plutonium contaminated wounds is difficult due to the lowenergy and yield of the uranium L-shell x rays used for the measurement, which can be effected by source distance, shape, and tissue attenuation. These effects on wound counting systems used at Los Alamos National Laboratory (LANL) were characterized experimentally using common source shapes (disk, point, and line) and acrylic plastic as a tissue substitute. Experiments were conducted to characterize detector responses as a function of tissue attenuation, source distance, and source depth in tissue. The computer code MCNP5 was used to model both systems for wound counting and better examine angular displacement of a line source in tissue. The NaI(Tl) detector response was characterized using absolute detector efficiency for all experimental measurements. Measurements showed that the NaI(Tl) system is significantly effected by the source to detector position and depth in tissue. Characterization of the HPGe detection system was done utilizing the peak-to-peak ratio from the two low-energy x rays. HPGe peak-to-peak ratios were not affected by source to detector distance, but showed an increased response to source depth in tissue. MCNP results suggested that small incident angles from the plane of the detector face can cause significant effects on the response of both detectors. In summary, the response of both systems showed dependence on source geometry and depth of contamination in tissue. Correction values and uncertainties were determined based on these dependencies.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-04-27T13:49:02Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) ISABEL CRISTINA GUERRA SPACOV -TESE DE DOUTORADO - PROTEN.pdf: 6093450 bytes, checksum: ace1719e245c067e138dff5b29870857 (MD5) / Made available in DSpace on 2017-04-27T13:49:02Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) ISABEL CRISTINA GUERRA SPACOV -TESE DE DOUTORADO - PROTEN.pdf: 6093450 bytes, checksum: ace1719e245c067e138dff5b29870857 (MD5) Previous issue date: 2016-09-09 / A Província Pegmatítica da Borborema no Nordeste é uma das mais importantes áreas geoeconômicas do Brasil. A atividade de mineração, entretanto, pode elevar a exposição de trabalhadores do setor, às radiações ionizantes. A exposição às radiações no setor mineral depende de uma série de fatores, incluindo o tipo de mina e geologia local, com elevadas concentrações de radionuclídeos que compoem as séries do 238U e do 232Th. Este trabalho teve como objetivo realizar a dosimetria radiométrica ambiental externa, estimando a taxa de dose efetiva em doze minas de extração de caulim, granito, feldspato e scheelita, localizadas nos municípios de Junco do Seridó-PB, Salgadinho-PB, Santa Luzia-PB, São José do Sabugi-PB, Equador-RN e Santana do Seridó-RN. O monitoramento foi executado utilizando um espectrômetro gama portátil NaI(Tl) e BGO, com medições realizadas no ar e os resultados obtidos foram comparados a dose efetiva média mundial da exposição à fontes naturais de radiação, de 2,40 mSv/a, baseada no relatório da UNSCEAR. O valor obtido da média aritmética das taxas de doses efetivas foi de 3,34 mSv/a e desvio padrão de 2,47 mSv/a para as minas em conjunto, estando acima do valor de referência mundial, bem como as taxas de doses efetivas das minas de granito (5,80 mSv/a), feldspato (3,28 mSv/a) e scheelita (2,80 mSv/a). Com base nesse estudo, foi evidenciada uma maior radioatividade ambiental na mina de granito (E), em Santa Luzia-PB (11,60 mSv/a), estando superior, cerca de cinco vezes, ao valor de referência mundial. É, portanto, considerada uma área de elevado backgound natural, com taxa de dose variando de 5 a 20 mSv/a, assim como a zona rural de São José de Espinharas-PB, onde se encontra a jazida de urânio com média de 10,83 mSv/a, ambos na região do Seridó. Por sua vez, apesar do valor médio da taxa de dose efetiva das minas de caulim (1,78 mSv/a) estarem abaixo do valor de referência mundial, a caracterização radiométrica da mina de caulim (D) em Salgadinho-PB, se faz necessária, tendo em vista o valor de 2,94 mSv/a. Desta forma, recomenda-se também, estudos epidemiológicos de casocontrole, coorte e correlação geográfica, que tratem de padrões, causas e quantificação dos valores obtidos na dosimetria ambiental deste estudo, bem como da relação da incidência e prevalência das doenças causadas pela exposição em áreas de elevado background natural. / The Pegmatitic Borborema Province located in the Northeast of Brazil, is one of the most important geo-economic areas in the country. The mining activity, however, can increase the exposure of workers to ionizing radiation. Exposure to radiation in the mineral industry depends on a number of factors, including the type of mine and local geology, with high concentrations of radionuclides which compose the series of 238U and 232Th. This study aimed to carry out the external environmental radiometric dosimetry, estimating the effective dose rate in twelve mines of kaolin, granite, feldspar and scheelite extraction, located in Junco do Seridó-PB, Salgadinho-PB, Santa Luzia-PB, São José do Sabugi-PB, Equador-RN and Santana do Seridó-RN. The monitoring was performed using a spectrometer portable gamma NaI(Tl) and BGO, with measurements in the air and the results were compared to the global average effective dose of exposure to natural sources of radiation of 2.40 mSv/y, based on the UNSCEAR report. The obtained value of the arithmetic mean of the effective dose rate was 3.34 mSv/y from the twelve mines, being above the global reference value, as well as the rates of effective doses of granite mine (5.80 mSv/y), feldspar (3.28 mSv/y) and scheelite (2.80 mSv/y). Based on this study, greater environmental radioactivity in granite mine (E) was observed in Santa Luzia-PB (11.60 mSv/y), being higher, about five times to the global reference value. It is therefore considered an area of high natural background with dose rate ranging from 5 to 20 mSv/y, as well as the São José de Espinharas-PB, where the uranium deposit is located, with an average of 10.83 mSv/y, both in the Seridó region. Meanwhile, although the average value of the effective dose rate of kaolin mine (1.78 mSv/y) is below the world reference value, the radiometric characteristics of the kaolin mine (D) Salgadinho-PB are necessary, in view of the value of 2.94 mSv/y. Thus, also recommended are studies, epidemiological case-control, cohort and geographical correlation, to address patterns, causes and quantization of values obtained in the environmental dosimetry of this study, as well as the relationship of the incidence and prevalence of diseases caused by exposure in areas of high natural background.

The response of low energy nuclear recoil in NaI(Tl) is investigated in the following experiment. Such detectors have been used recently to search for evidence of dark matter in the form of weakly interacting massive particles (WIMPs). NaI(Tl) crystal response to nuclear recoil energy deposition is a key element in these searches. I discuss the cosmological and experimental motivations for these experiments, followed by an overview of the physics of direct detection and current relevant WIMP search experiments. With the experiment motivations covered, the details of NaI(Tl) detectors are reviewed. The specifics of our experiment are laid out including the neutron production, neutron beam calibration, shielding optimization, experimental design and setup. Then the crystal response calibration studies and Geant4 simulations are discussed followed by the final quenching factor values and uncertainties. This experiment measured quenching factors for sodium recoils in the energy range of (9 keV-40 keV) of 19%-27% QF. These results are similar to current published measurements. Interesting features of the QF measurements include an increase at low energies and a dip in the values at 30 keV, the iodine K-shell absorption edge. The goal of this experiment was to add valuable measurements of nuclear recoils at low energies that are relevant to low-mass WIMP experiments. Future plans will improve and expand on these measurements in order to better understand the response of NaI(Tl) at low energies.

Submitted by Almir Azevedo (barbio1313@gmail.com) on 2018-05-09T13:11:49Z No. of bitstreams: 1 dissertação mestrado ien 2018 Tamara Porfiro Teixeira.pdf: 807837 bytes, checksum: b01215afaee9c4a8b22c3267552cfcbc (MD5) / Made available in DSpace on 2018-05-09T13:11:49Z (GMT). No. of bitstreams: 1 dissertação mestrado ien 2018 Tamara Porfiro Teixeira.pdf: 807837 bytes, checksum: b01215afaee9c4a8b22c3267552cfcbc (MD5) Previous issue date: 2018-02 / Este trabalho apresenta uma metodologia para predição de incrustação concêntricas e excêntricas em tubulações utilizadas na indústria de petróleo off-shore. A aproximação é baseada nos princípios de densitometria gama e redes neurais artificiais. Foi desenvolvido um modelo de estudo preliminar visando definir as composições do duto e incrustações. Para isso, foi avaliada a influência na transmissão gama de dutos com quatro tipos diferentes de aços utilizados em plataformas de petróleo, bem como a influência das principais formações inorgânicas de depósitos. A divergência da fonte radioativa também foi considerada nessa avaliação, com aberturas de colimação de 2 mm a 7 mm, com passos de 2,5 mm. Após a definição da composição do duto e incrustação, foi definida uma geometria de medição por meio do código MCNP-X para calcular a espessura da incrustação por meio de equações analíticas independentemente dos fluidos presentes no duto (água salgada, gás e óleo). A geometria representativa utiliza um duto composto por Ferro, com incrustação inorgânica formada por sulfato de bário (BaSO4). Modelos de incrustações concêntricas foram simulados e os dados obtidos foram utilizados para treinamento e validação de uma rede neural artificial, bem como modelos de incrustações excêntricas. O sistema de detecção simulado consistiu em uma geometria com feixe estreito com 2 mm de abertura de colimação, compreendendo uma fonte de raios gama (137Cs) e detectores NaI(Tl) 2x2” posicionados adequadamente ao redor do sistema duto-incrustação-fluido para o cálculo da espessura de incrustação considerando o feixe transmitido e o espalhado. O espalhamento Compton foi considerado nos casos de incrustações com formação excêntrica para auxílio na determinação e localização das espessuras máximas de incrustação. Os modelos teóricos foram desenvolvidos usando o código matemático MCNPX e utilizados para o treinamento, teste e validação das redes neurais artificiais. A metodologia proposta foi capaz de predizer as espessuras de incrustações concêntricas e excêntricas com resultados satisfatórios para esses dois tipos de formações inorgânicas. / This work presents a methodology for predicting concentric and eccentric scales in pipelines used in the offshore oil industry. The approximation is based on the principles of gamma densitometry and artificial neural networks. A preliminary study model was developed to define the compositions of the duct and scale. In order to do so, the influence of pipeline transmission with four different types of steel used in oil platforms was evaluated, as well as the influence of the main inorganic deposit formations. The divergence of the radioactive source was also considered in this evaluation, with collimation openings of 2 mm to 7 mm, with steps of 2.5 mm. After defining the composition of the duct and scale, a measurement geometry was defined by means of the MCNP-X code to calculate the scale thickness by means of analytical equations, independent of the fluids present in the duct (salt water, gas and oil). The representative geometry uses a duct composed of iron, with inorganic scale formed by barium sulfate (BaSO4). Concentric scale models were simulated and the data obtained were used for training and validation of an artificial neural network, as well as eccentric scale models. The simulated detection system consisted of a narrow-beam geometry with a 2 mm collimation aperture, comprising a gamma ray source (137Cs) and 2x2 "NaI (Tl) sensors suitably positioned around the duct-scale-fluid system for calculation of the scale thickness considering the transmitted beam and the scattered beam. Compton scattering was considered in cases of eccentric scale to aid in the determination and location of maximum scale thicknesses. The theoretical models were developed using the mathematical code MCNP-X and used for training, testing and validation of artificial neural networks. The proposed methodology was able to predict the concentric and eccentric scale thicknesses with satisfactory results for these two types of inorganic formations.

The decay of 33 hour ¹⁴³Ce to levels in ¹⁴³Pr has been studied, using Ge(Li), NaI(Tl), and Si detectors. A number of new gamma ray transitions have been discovered. A decay scheme based on the experimental results is discussed and some spin assignments are suggested. This investigation was not exhaustive and suggestions are made as to further experiments which could be done. / Thesis / Master of Science (MSc)

Submitted by Marcele Costal de Castro (costalcastro@gmail.com) on 2017-09-27T15:49:43Z No. of bitstreams: 1 CESAR MARQUES SALGADO D.PDF: 3287236 bytes, checksum: e8cb423520d25b201049a40e5dc0babf (MD5) / Made available in DSpace on 2017-09-27T15:49:43Z (GMT). No. of bitstreams: 1 CESAR MARQUES SALGADO D.PDF: 3287236 bytes, checksum: e8cb423520d25b201049a40e5dc0babf (MD5) Previous issue date: 2010-02 / Este trabalho apresenta uma nova metodologia baseada nos princípios de atenuação de raios gama, por meio de simulações de Monte Carlo (MC), e redes neurais artificiais (RNAs) supervisionadas para predições de frações de volume e identificação de regimes de fluxo em sistemas multifásicos tipo, gás, água e óleo encontrados na indústria petrolífera off-shore. O princípio baseia-se no reconhecimento das distribuições de altura de pulsos obtidas por detectores cintiladores que são utilizadas inteiramente para alimentar de forma simultânea as RNAs. As curvas-resposta (resolução energética e eficiência) de um detector real são consideradas. O sistema de detecção simulado utiliza dois detectores NaI(Tl) e duas energias de raios gama com feixe largo. A geometria proposta considera os feixes transmitido e espalhado tornando o sistema menos dependente do regime de fluxo. O conjunto de padrões necessário para treinamento e avaliação das RNAs foi gerado por meio do código computacional MCNP-X baseado no método de MC a partir de modelos teóricos ideais e estáticos de regimes multifásicos - anular, estratificado e homogêneo. As RNAs mapearam adequadamente os dados simulados com as frações de volume sem a necessidade do conhecimento, a priori, do regime de fluxo. As RNAs identificaram corretamente todos os regimes com predição satisfatória das frações de volume em sistemas multifásicos indicando a possibilidade de aplicação desta metodologia para tal propósito. / This work presents a new methodology for flow regimes identification and volume fractions prediction in gas-water-oil multiphase systems found in off-shore petroleum industry. The approach is based on gamma-ray pulse height distributions (PHDs) pattern recognition by means the artificial neural networks (ANNs). The detection system uses appropriate fan beam geometry, comprised of a dual-energy gamma-ray source and two NaI(Tl) detectors adequately positioned in order calculate transmitted and scattered beams, which makes it less dependent on the flow regime. The system comprises four ANNs, the first identifies the flow regime and the other three ANNs are specialized in volume fraction prediction for each specific regime. The PHDs are directly used by the ANNs without any parameterization of the measured signal. The energy resolution and efficiency of NaI(Tl) detectors are also considered on the mathematical model. The ideal and static theoretical models for annular, stratified and homogenous flow regimes have been developed using MCNP-X mathematical code (simulations by means of Monte Carlo method), which was used to provide training, test and validation data for the ANNs. The proposed ANNs could correctly identified all three different regimes with satisfactory prediction of volume fraction in gas-water-oil multiphase system demonstrating to be a promising approach for this purpose.

Missing page viii. Page 171 was repeated with different text. / <p> The decay of 14.9 min. ⁸⁹Rb to levels in ⁸⁹Sr has been studied by use of Ge(Li) detectors, NaI(Tl) detectors and a magnetic beta ray spectrometer. Fourteen gamma rays have been studied by ɣ-ɣ and β-ɣ coincidence experiments and establish levels at 0, 1.031, 2,000, 2.277, 2.567, 2.708, 2.770, 3.225 and 3.500 MeV. The Q value is 4.486 ± .012 Mev. </p> <p> The techniques of beta and gamma ray spectroscopy using Ge(Li), NaI(Tl) and plastic beta detectors have been applied in the study of the decay of 3.2 min. ⁸⁹Kr to levels in ⁸⁹Rb. Seventy nine of the one hundred and eleven observed gamma rays have been classified in the proposed decay scheme. The Q value is 5.15 ± .03 MeV. </p> / Thesis / Doctor of Philosophy (PhD)

The detonation of a radiological dispersion device (RDD) may result in a situation where many individuals are exposed to contamination due to the inhalation of radioactive materials. Assessments of contamination may need to be performed by emergency response personnel in order to triage the potentially exposed public. The feasibility of using readily available standard 2x2-inch sodium-iodide detectors to determine the committed effective dose to a patient following the inhalation of a radionuclide has been investigated. The 2x2-NaI(Tl) detector was modeled using the Monte Carlo simulation code, MCNP-5, and was validated via a series of experimental benchmark measurements using a polymethyl methacrylate (PMMA) slab phantom. Such validation was essential in reproducing an accurate detector response. Upon verification of the detector model, six anthropomorphic phantoms, based on the MIRD-V phantoms, were modeled with nuclides distributed to simulate inhaled contamination. The nuclides assessed included Am-241, Co-60, Cs-137, I-131, and Ir-192. Detectors were placed at four positions on the phantoms: anterior right torso, posterior right torso, anterior neck, and lateral left thigh. The detected count-rate varied with respect to detector position, and the optimal detector location was determined on the body. The triage threshold for contamination was set at an action level of 250-mSv of intake. Time dependent biokinetic modeling was employed to determine the source distribution and activity in the body as a function of post-inhalation time. The detector response was determined as a function of count-rate per becquerel of activity at initial intake. This was converted to count-rate per 250-mSv intake for triage use by first responders operating the detector to facilitate triage decisions of contamination level. A set of procedure sheets for use by first responders was compiled for each of the phantoms and nuclides investigated.