L'objectif de cette thèse vise à mettre au point et à améliorer les méthodes de mesures d'échauffements nucléaires auprès des maquettes critiques du CEA-Cadarache EOLE et MINERVE, au moyen de détecteurs thermo-luminescents (TLD), de détecteurs à luminescence optiquement stimulée (OSLD – nouvellement mis en œuvre dans le cadre de ce travail de thèse) et d'une chambre d'ionisation. Il s'agit d'identifier, de hiérarchiser, de traiter et enfin de réduire les différentes sources d'incertitudes et de biais systématiques associés à la mesure.Une série d'expériences a été mise en place dans le réacteur MINERVE. Les mesures ont été réalisées dans un environnement en aluminium ou en hafnium à l'aide d'un nouveau protocole : les TLD ont été étalonnés individuellement, la répétabilité de la mesure a été évaluée expérimentalement et les lois de chauffe des TLD ont été optimisées, conduisant à une réduction des incertitudes de mesures. Des mesures de gammas émis de façon différée après arrêt du réacteur MINERVE ont également été réalisées : les résultats obtenus montrent un bon accord des mesures avec les trois types de détecteurs utilisés.L'interprétation de ces mesures nécessite des calculs pour tenir compte des facteurs de correction, liés à l'environnement et au type de détecteurs utilisés. Ainsi, des corrections de la contribution des neutrons à la dose totale intégrée par les détecteurs ont été évaluées à l'aide de deux méthodes de calcul. Ces corrections ont été obtenues sur la base de simulations Monte Carlo couplées neutron-gamma et gamma-électron à l'aide du code MCNP. / The objective of this thesis is to develop and to improve the nuclear heating measurement methods in MINERVE and EOLE experimental reactors at CEA-Cadarache, using thermo-luminescent detectors (TLD), optically stimulated luminescence detectors (OSLD – newly implemented in the context of this thesis) and an ionization chamber. It is to identify, prioritize, treat and reduce the various sources of uncertainty and systematic bias associated with the measurement.A series of experiments was set up in the MINERVE reactor. The measurements were carried out in an aluminum or hafnium surrounding using a new procedure methodology. The TLD are calibrated individually, the repeatability of the measurement is experimentally evaluated and the laws of TLD heat are optimized. The measurements of the gamma emitted, with a delay (delayed gamma) after shutdown of the MINERVE reactor, were also carried out using TLD and OSLD detectors with the aluminum pillbox as well as by ionization chamber. The results show a good correlation between the measurements recorded by these three detectors.The interpretation of these measurements needs to take account the calculation of cavity correction factors related to the surrounding and the type of detector used. Similarly, the correction due to the neutrons contributions to the total dose integrated by the detectors are evaluated with two calculation methods. These corrections are based on Monte Carlo simulations of neutron-gamma and gamma-electron transport coupled particles using the MCNP.

Résumé en français confidentiel / Résumé en anglais confidentiel

Vidros com composição de aluminofosfato vêm sendo estudados por apresentarem elevada durabilidade química. O objetivo do presente trabalho foi estudar as propriedades térmicas e estruturais do sistema vítreo xKPO3 - (100-x)Al(PO3)3, para x = 10, 30 e 50 (% em mol), a fim de determinarmos uma composição que apresentasse uma boa resposta termoluminescente (TL) quando dopada com íons de manganês. As matrizes vítreas não dopadas apresentaram uma boa estabilidade vítrea frente a devitrificação. As fases cristalizadas no sistema foram determinadas por difração de raios X e espectroscopia micro-Raman como KAIP2O7 e AI(PO3)3. A composição KAI(PO3)4 (x = 50 %) apresentou elevada durabilidade química e o menor ponto de fusão, o que facilitou o processo de preparação. Essa composição foi então utilizada para as dopagens com íons de manganês. A composição com 1,0 % em mol de MnO2 apresentou a melhor resposta TL. As propriedades dosimétricas estudadas mostraram que o vidro possui uma resposta linear para raios X no intervalo de dose de 2 mGy a 80 Gy, podendo então ser utilizado em dosimetria clínica e pessoal / Aluminophosphate glasses have been studied because of their good chemical resistance. The main purpose of this work was to investigate the structural and thermal properties of glasses in the system xKPO3 - (100-x)AI(PO3)3, with x = 10, 30 e 50 (mol %). The goal was to determine a composition which provided a good thermoluminescence response (TL) when doped with manganese ions. The undoped vitreous matrixes showed a good thermal stability against devitrification. The crystalline phases were identified by X ray diffraction and micro-Raman spectroscopy as KAIP2O7 and Al(PO3)3. The composition KAI(PO3)4 (x = 50 %) showed high chemical resistance and lower melting point. This composition was used for doping with manganese ions. The composition of 1,0 mol % of MnO2 showed the best TL response. The dosimetric properties showed that this glass has a linear response for X-rays in the dose interval of 2 mGy to 80 Gy, and it is a promising material for application as a TLD dosimeter

Ao implementar uma técnica de tratamento, as características do feixe nas condições de irradiação precisam ser bem conhecidas e estudadas. Cada um dos parâmetros utilizados para cálculo de dose deve ser medido e validado antes da utilização dos mesmos na rotina clínica. Isso se torna ainda mais necessário quando se tratam de técnicas especiais. Neste trabalho estão descritos todos os parâmetros e medidas necessárias para a implementação da irradiação de corpo inteiro numa instalação projetada para tratamentos convencionais, e que faz uso de geometrias não convencionais para gerar os tamanhos de campos alargados. Além disso, são apresentados os dados de comissionamento desta modalidade no Hospital das Clínicas de São Paulo utilizando a comparação de três tipos de detectores para medidas de dose de entrada durante tratamentos de irradiação de corpo inteiro. / Before implementing a treatment technique, the characteristics of the beam under irradiation conditions must be well acknowledged and studied. Each one of the parameters used to calculate the dose has to be measured and validated before its utilization in clinical practice. This is particularly necessary when dealing with special techniques. In this work, all necessary parameters and measurements are described for the total body irradiation implementation in facilities designed for conventional treatments that make use of unconventional geometries to generate desired enlarged field sizes. Furthermore, this work presents commissioning data of this modality at Hospital das Clínicas of São Paulo using comparison of three detectors types for measurements of entrance dose during total body irradiation treatment.

Ao implementar uma técnica de tratamento, as características do feixe nas condições de irradiação precisam ser bem conhecidas e estudadas. Cada um dos parâmetros utilizados para cálculo de dose deve ser medido e validado antes da utilização dos mesmos na rotina clínica. Isso se torna ainda mais necessário quando se tratam de técnicas especiais. Neste trabalho estão descritos todos os parâmetros e medidas necessárias para a implementação da irradiação de corpo inteiro numa instalação projetada para tratamentos convencionais, e que faz uso de geometrias não convencionais para gerar os tamanhos de campos alargados. Além disso, são apresentados os dados de comissionamento desta modalidade no Hospital das Clínicas de São Paulo utilizando a comparação de três tipos de detectores para medidas de dose de entrada durante tratamentos de irradiação de corpo inteiro. / Before implementing a treatment technique, the characteristics of the beam under irradiation conditions must be well acknowledged and studied. Each one of the parameters used to calculate the dose has to be measured and validated before its utilization in clinical practice. This is particularly necessary when dealing with special techniques. In this work, all necessary parameters and measurements are described for the total body irradiation implementation in facilities designed for conventional treatments that make use of unconventional geometries to generate desired enlarged field sizes. Furthermore, this work presents commissioning data of this modality at Hospital das Clínicas of São Paulo using comparison of three detectors types for measurements of entrance dose during total body irradiation treatment.

<p>Patient dose in diagnostic radiology is usually expressed in terms of organ dose and effective dose. The latter is used as a measure of the stochastic risk. Determinations of these doses are obtained by measurements (Thermoluminescent dosemeters) or by calculations (Monte Carlo simulation).</p><p>Conversion factors for the calculation of effective dose from dose-area product (DAP) values are commonly used to determine radiation dose in conventional x-ray imaging to realize radiation risks for different investigations, and for different ages. The exposure can easily be estimated by converting the DAP into an effective dose.</p><p>The aim of this study is to determine the conversion factor in procedures by computing the ratio between effective dose and DAP for fluoroscopic cardiac procedures in adults and for conventional lung and urography examinations in children.</p><p>Thermoluminescent dosemeters (TLD) were placed in an anthropomorphic phantom (Alderson Rando phantom) and child phantom (one year old) in order to measure the organ dose and compute the effective dose. A DAP meter was used to measure dose-area product.</p><p>MC calculations of radiation transport in mathematical anthropomorphic phantoms were used to obtain the effective dose for the same conditions with DAP as input data.</p><p>The deviation between the measured and calculated data was less than 10 %. The conversion factor for cardiac procedures varies between 0.19 mSvGy-1 cm-2 and 0.18 mSvGy-1 cm-2, for TLD respective MC. For paediatric simulation of a one year old phantom the average conversion factor for urography was 1.34 mSvGy-1 cm-2 and 1,48 mSvGy-1cm-2 for TLD respective MC. This conversion factor will decrease to 1.07 mSvGy-1 cm-2 using the TLD method, if the new ICRP (ICRP Publication 103) weighting factors were used to calculate the effective dose.</p><p>For lung investigations, the conversion factor for children was 1.75 mSvGy-1 cm-2 using TLD, while this value was 1.62 mSvGy-1 cm-2 using MC simulation. The conversion value increased to 2.02 mSvGy-1 cm-2 using ICRP’s new recommendation for tissue weighting factors and child phantom.</p>

Patient dose in diagnostic radiology is usually expressed in terms of organ dose and effective dose. The latter is used as a measure of the stochastic risk. Determinations of these doses are obtained by measurements (Thermoluminescent dosemeters) or by calculations (Monte Carlo simulation). Conversion factors for the calculation of effective dose from dose-area product (DAP) values are commonly used to determine radiation dose in conventional x-ray imaging to realize radiation risks for different investigations, and for different ages. The exposure can easily be estimated by converting the DAP into an effective dose. The aim of this study is to determine the conversion factor in procedures by computing the ratio between effective dose and DAP for fluoroscopic cardiac procedures in adults and for conventional lung and urography examinations in children. Thermoluminescent dosemeters (TLD) were placed in an anthropomorphic phantom (Alderson Rando phantom) and child phantom (one year old) in order to measure the organ dose and compute the effective dose. A DAP meter was used to measure dose-area product. MC calculations of radiation transport in mathematical anthropomorphic phantoms were used to obtain the effective dose for the same conditions with DAP as input data. The deviation between the measured and calculated data was less than 10 %. The conversion factor for cardiac procedures varies between 0.19 mSvGy-1 cm-2 and 0.18 mSvGy-1 cm-2, for TLD respective MC. For paediatric simulation of a one year old phantom the average conversion factor for urography was 1.34 mSvGy-1 cm-2 and 1,48 mSvGy-1cm-2 for TLD respective MC. This conversion factor will decrease to 1.07 mSvGy-1 cm-2 using the TLD method, if the new ICRP (ICRP Publication 103) weighting factors were used to calculate the effective dose. For lung investigations, the conversion factor for children was 1.75 mSvGy-1 cm-2 using TLD, while this value was 1.62 mSvGy-1 cm-2 using MC simulation. The conversion value increased to 2.02 mSvGy-1 cm-2 using ICRP’s new recommendation for tissue weighting factors and child phantom.

Brachytherapy is a form of radiotherapy in which radioactive sources are placed at short distances from, or even inside the target volume. The use of high dose rate brachytherapy is a widely accepted and clinically proven treatment for some stages of prostate cancer. The aim of this project was to investigate potential improvements on two of the most important aspects of high dose rate (HDR) and pulsed dose rate (PDR) prostate brachytherapy - prostate definition and treatment delivery verification. The use of magnetic resonance (MR) imaging in addition to the conventional computed tomography (CT) imaging methods currently used routinely for brachytherapy planning may provide some benefit in accurately defining the prostate and surrounding critical structures. The methods used in this project involved analysis of data sets provided by two Radiation Oncologists. The results presented showed inter-observer and intra-observer variations in the size and shape of the prostate, as well as analysis of the dosimetric differences that may be reported due to the differences in prostate size and shape. The results also included analysis of critical structure dosimetry - dose to the surrounding radio-sensitive rectum and urethra. In summary, the results showed that the prostate was defined to be smaller using MR imaging than CT, however the consistency between Oncologists was not significantly improved using MR imaging. MR imaging may be useful in reducing the dose to normal tissue surrounding the prostate and in obtaining better coverage of the smaller target volume, without compromising the critical structures. The use of LiF:Mg,Ti thermoluminescent dosimeters (TLDs) is a potential avenue for in vivo dose verification of an HDR or PDR prostate brachytherapy treatment plan. This project included a phantom study of these TLDs with the aim to determine their feasibility for clinical use. Cylindrical TLD rods (6 mm length x 1 mm diameter) were used, as these fit inside the brachytherapy needles implanted into the prostate, and therefore had potential to be used clinically to verify the dose delivered in the prostate. This study was extended to include determination of a correction factor to allow an independent radiation source (6 MV photon beam from a linear accelerator) to be used to obtain control readings for this relative dosimetric method. The results showed these TLDs to be a promising in vivo dosimeter for prostate brachytherapy with potential errors in the order of 4%. Their potential lies in the fact that they could detect and flag significant calculation errors in treatment plans, and they utilise equipment used routinely for external beam radiotherapy dosimetry in many treatment facilities, reducing the cost of implementing such a procedure.

Vidros com composição de aluminofosfato vêm sendo estudados por apresentarem elevada durabilidade química. O objetivo do presente trabalho foi estudar as propriedades térmicas e estruturais do sistema vítreo xKPO3 - (100-x)Al(PO3)3, para x = 10, 30 e 50 (% em mol), a fim de determinarmos uma composição que apresentasse uma boa resposta termoluminescente (TL) quando dopada com íons de manganês. As matrizes vítreas não dopadas apresentaram uma boa estabilidade vítrea frente a devitrificação. As fases cristalizadas no sistema foram determinadas por difração de raios X e espectroscopia micro-Raman como KAIP2O7 e AI(PO3)3. A composição KAI(PO3)4 (x = 50 %) apresentou elevada durabilidade química e o menor ponto de fusão, o que facilitou o processo de preparação. Essa composição foi então utilizada para as dopagens com íons de manganês. A composição com 1,0 % em mol de MnO2 apresentou a melhor resposta TL. As propriedades dosimétricas estudadas mostraram que o vidro possui uma resposta linear para raios X no intervalo de dose de 2 mGy a 80 Gy, podendo então ser utilizado em dosimetria clínica e pessoal / Aluminophosphate glasses have been studied because of their good chemical resistance. The main purpose of this work was to investigate the structural and thermal properties of glasses in the system xKPO3 - (100-x)AI(PO3)3, with x = 10, 30 e 50 (mol %). The goal was to determine a composition which provided a good thermoluminescence response (TL) when doped with manganese ions. The undoped vitreous matrixes showed a good thermal stability against devitrification. The crystalline phases were identified by X ray diffraction and micro-Raman spectroscopy as KAIP2O7 and Al(PO3)3. The composition KAI(PO3)4 (x = 50 %) showed high chemical resistance and lower melting point. This composition was used for doping with manganese ions. The composition of 1,0 mol % of MnO2 showed the best TL response. The dosimetric properties showed that this glass has a linear response for X-rays in the dose interval of 2 mGy to 80 Gy, and it is a promising material for application as a TLD dosimeter

Submitted by Isaac Francisco de Souza Dias (isaac.souzadias@ufpe.br) on 2016-03-31T17:11:31Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese de Jairo Dias.pdf: 2064500 bytes, checksum: 77ff167e06534ac84843f461013c18c4 (MD5) / Made available in DSpace on 2016-03-31T17:11:31Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese de Jairo Dias.pdf: 2064500 bytes, checksum: 77ff167e06534ac84843f461013c18c4 (MD5) Previous issue date: 2015-08-07 / CAPES / Estudos radioecológicos com dosimetria ambiental vêm sendo realizados mundialmente, principalmente para avaliar os níveis de radiação natural oriundos dos radionuclídeos primordiais presentes na crosta terrestre, tais como o 40K e os radionuclídeos das séries do 238U e do 232Th. Estes radionuclídeos são os que mais contribuem para a exposição gama externa em ambientes fechados, principalmente quando localizados em áreas que apresentam níveis diferenciados de radiação natural. Neste contexto, o presente trabalho teve como objetivo, determinar as taxas de doses efetivas externas dentro das residências, dose “indoor”, localizadas próximas à jazida de urânio do município de São José de Espinharas no estado da Paraíba, que contêm altos níveis de radionuclídeos terrestres, os quais constituem os Materiais Radioativos de Ocorrências Naturais (NORM). Para caracterizar o estudo radiométrico, foram instalados 178 conjuntos de dosímetros termoluminscentes, com três TLDs do tipo LiF:Mg, Ti (Fluoreto de Lítio dopado com Magnésio e Titânio) nos quartos das residências, sendo substituídos a cada 90 dias. Toda pesquisa foi realizada no período de dezembro de 2012 a novembro de 2014. As taxas de doses efetivas ambientais calculadas para São José de Espinharas variaram de 0,71 a 2,07 mSv.a-1, com média de 0,90 mSv.a-1. Municípios adjacentes à área de estudo também foram monitorados no referido estudo, destacando-se: São Mamede, São José do Sabugi, Patos e Santa Luzia com valores intervalares e médias de 0,77 a 1,41 mSv.a-1 (0,94 mSv.a-1); 0,90 a 1,67 mSv.a-1 (1,13 mSv.a-1); 0,77 a 0,93 mSv.a-1 (0,87 mSv.a-1) e 1,10 a 1,27 mSv.a-1 (1,18 mSv.a-1), respectivamente. A média geral do referido estudo ficou em torno de 0,99  0,10 mSv.a-1, correspondendo a um valor médio que é 2,5 vezes superior ao estimado para ambientes fechados conforme o Comitê Científico das Nações Unidas para os Efeitos das Radiações Atômicas (UNSCEAR) que é 0,41 mSv.a-1. Estes valores conferem aos municípios, influências exclusivas de materiais radioativos de ocorrências naturais devido à formação geológica da região, quando levado em consideração os níveis desses radionuclídeos. Observa-se que os resultados obtidos nesta monitoração radioecológica, não permite propor nenhuma condição de contaminação "indoor" sem antes monitorar a água, os alimentos, os materiais de construção, como também os habitantes para se predizer qualquer condição de risco real que esteja associada a população desses municípios. / Radioecological studies of environmental dosimetry have been conducted worldwide, mainly to assess the natural levels of radiation coming from the primordial radionuclides present in the earth's crust, such as 40K and radionuclides from 238U and 232Th series. These radionuclides are the main contributors to external gamma exposure indoors, especially when they are located in areas with different levels of radiation. In this context, this study aimed to determine the external effective dose rates inside houses (indoor dose), located near the uranium mine in the city of São José de Espinharas in the state of Paraiba, Northeast region, Brazil, that contain high levels of terrestrial radionuclides, which are the Naturally. Occurring Radioactive Material (NORM). To characterize the radiometric study, were installed 178 sets of thermoluminescent dosimeters, with three TLDs type LiF: Mg, Ti (lithium fluoride doped with Magnesium and Titanium) each, in the rooms of the residences, these being replaced on average, every 90 days, from December 2012 to November 2014. Environmental effective doses rates calculated for São José de Espinharas varied from 0.71 to 2.07 mSv.y-1 with an average of 0.90 mSv.y-1. Municipalities adjacent to the study area were also monitored in the study, highlighting: São Mamede, São José do Sabugi, Patos and Santa Luzia with interval values and averages of 0.77 to 1.41 mSv.y-1 (0, 94 mSv.y-1); 0.90 to 1.67 mSv.y-1 (1.13 mSv.y-1); 0.77 to 0.93 mSv.y-1 (0.87 mSv.y-1) and 1.10 to 1.27 mSv.y-1 (1.18 mSv.y-1), respectively. The overall average of the study was around 0.99 ± 0.10 mSv.y-1, corresponding to an average of 2.5 times higher than the estimated for indoors according to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which is 0.41 mSv.y-1, giving the municipalities, exclusive influences of radioactive materials of natural occurrences, due to the geological formation of the region, when taken into consideration the levels of these radionuclides. It is observed that the results of this radioecological monitoring, does not allow to propose any "indoor" contamination condition without first monitor water, food, building materials, as well as the residents to predict any real risk factor for the population of these municipalities.