Ionizing radiation has a harmful potential to humans, so the protection of workers and public individuals is fundamental for the safe use of radiation in different practical purpose. Therefore, is necessary to set exposure limits to radiation using dosimetric quantities such as equivalent dose and effective dose. However equivalent and effective dose are not directly measured, so it is necessary calculate conversion coefficients (CCs) which relates this quantities with measured quantities such as particles fluence. In the literature exposure scenarios are, in general, built with simulator in the standing posture, but exposure of individuals to radiation can occur in other posture, so the aim of this work is calculate and compare the absorbed dose-to-fluence conversion coefficients (DT/ ) and effective dose-to-fluence conversion coefficients (E/ ) for the female hybrid simulator (UFHADF) in the standing and sitting posture and for the male hybrid simulator (UFHADM) in the standing posture using the Monte Carlo code MCNPX for monoenergetic protons from 2 MeV to 10 GeV and in the antero posterior (AP), postero anterior (PA), right lateral (RLAT), left lateral (LLAT), rotational (ROT) and isotropic (ISO) exposure scenarios. Comparing the CCs between standing and sitting posture of UFHADF simulator, it was observed that in the AP and PA irradiation geometry the relative differences in the head, chest and the superior abdomen organs were not relevant. However in the others irradiation geometries, for some organs in the abdomen and chest region differences in CCs were observed. The organs that presented more differences in CCs were uterus (538 % in RLAT geometry), bladder (80 % in ROT geometry) and ovaries (2861 % in LLAT geometry) since this organs are located in the lower abdominal region, in which the position of legs and arms are different between standing and sitting posture. Calculate the DT/ e E/ nconversion coefficients using simulator in the sitting posture is important to estimate more precisely the dose in individuals exposed to radiation in actual scenarios. / As radiacoes ionizantes tem um potencial danoso aos seres humanos e, por isso, a protecao de trabalhadores e de individuos do publico e essencial para o uso seguro das mesmas nos diversos fins praticos. Desta forma, e necessario estabelecer limites de exposicao com relacao a estes tipos de radiacao e, para tanto, sao utilizadas grandezas dosimetricas como a dose equivalente e a dose efetiva. Como a dose equivalente e a dose efetiva nao sao medidas diretamente faz-se necessario o calculo de coeficientes de conversao (CCs) em ambito computacional, pois eles relacionam estas grandezas com grandezas mensuraveis, como a fluencia de particulas. Como na literatura os cenarios de exposicao sao, em geral, construidos com simuladores implementados na postura vertical e nem sempre a exposicao de individuos a radiacao ocorre nessa postura, esse trabalho tem como finalidade, utilizar o codigo de transporte de radiacao Monte Carlo MCNPX e o simulador antropomorfico adulto feminino UFHADF nas posturas vertical e sentada e o simulador masculino UFHADM na postura vertical para obter e comparar os coeficientes de conversao para dose absorvida (DT) e dose efetiva (E) em termos da fluencia (X) (DT/X e E/X) para protons monoenergeticos de 2 MeV ate 10 GeV, para os cenarios de irradiacao antero-posterior (AP), postero-anterior (PA), lateral direito (RLAT), lateral esquerdo (LLAT), rotacional (ROT) e isotropico (ISO). Na comparacao dos CCs entre o simulador UFHADF nas posturas vertical e sentada, foi observado que a diferenca relativa entre os CCs nos orgaos da regiao da cabeca, do torax e do abdomen superior nao foram relevantes nas geometrias de irradiacao AP e PA. Ja nas demais geometrias de irradiacao, para alguns orgaos da regiao do abdomen e torax diferencas nos CCs foram observadas. Os orgaos que mais apresentaram diferencas nos CCs foram o utero (538 % na geometria RLAT), a bexiga (80 % na geometria ROT) e os ovarios (2861 % na geometria LLAT) que se localizam na regiao abdominal inferior, regiao onde ha a diferenca na posicao das pernas e bracos do simulador. Assim, o calculo dos coeficientes de conversao DT/ e E/ utilizando simuladores antropomorficos na postura sentada e importante para uma estimativa mais precisa da dose em individuos submetidos a cenarios reais de exposicao a radiacao.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Total Body Irradiation is a special technique of radiotherapy used for conditioning for bone marrow transplantation. Its function is to immunosuppression, bone marrow ablation and destruction of malignant cells. How it is the irradiation of a large and irregular field is necessary to seek ways to offset the tissues so that the absorbed dose to the patient's body has a uniformity of ± 10%. In addition, other factors intervene so that this condition is satisfied, such as the choice of radiation source, the posture of the patient, the incidence geometry, the distance of treatment, the combination of fields, among others. To analyze how these factors influence the dose distribution in the body, in this study we were simulated computationally scenarios of Total Body Irradiation, using telecobaltherapy units and linear accelerator of 6 MV, for an estimated equivalent and effective doses using the code MCNPX of radiation transport and hybrid anthropomorphic simulators UFHADF and UFHADM in sitting postures to RLAT and LLAT irradiation, and lying to the AP and PA projections. To validate the spectra used in the simulations was calculated PDP for comparison with experimental measurements. As for the validation of TBI scenarios were estimated entrance dose rates in skin also for comparison with experimental measurements. The PDP curves are shown according to the literature. The values of the estimated dose rates are less than 10% relative difference in relation to the experimental measurements, which allowed us to estimate the dose in the organs. The simulation results show that the lateral irradiations of UF simulators in the sitting posture offer a less uniform dose distribution compared to radiation AP / PA with the simulator in lying posture. For the PA irradiation geometry the absorbed dose in the red marrow is approximately 20% higher than in the AP projection, which suggests that the first case is most appropriate for the destruction of diseased marrow. Regarding the use of attenuators objects for radiation attenuation in the lung there was a reduction of 23% of the absorbed dose by this organ, which shows their effectiveness and importance to these procedures. It was also observed that the decrease in patient treatment away from the radiation source and the room walls leads to a near increase of 10% and 5%, respectively, the absorbed dose, which suggests that treatments be more suitable carried out great distances focus-surface and far from the room's walls. The energy beam used for Total Body Irradiation, the most significant differences between the Cobalt-60 and linear accelerator 6 MV spectra were up to 46.23%, which occurred for the AP irradiation geometry, where observed that the first deposits most of its energy near the surface, which shows that more energy beams for irradiation are more effective at greater depths. Another factor analyzed was the combination of adjacent and overlapping fields for the treatment, leading to overdoses in some organs and committed dose uniformity as observed by other authors. The calculation of the effective dose showed that there is a greater overall commitment of the body to radiation in LLAT incidence geometry. It was also found that the effective dose is higher in the AP projection than PA as found in the literature. The analyzes show the importance and suggest a more detailed study of the exposure conditions for planning treatments for TB / A Irradiação de Corpo Inteiro é uma técnica especial de radioterapia utilizada para o condicionamento de transplante de medula óssea. Sua função é de imunossupressão, ablação da medula e destruição de células malignas. Por se tratar da irradiação de um campo grande e irregular é necessário buscar meios para compensação dos tecidos para que a dose absorvida pelo corpo do paciente tenha uma uniformidade de ±10%. Além disso, outros fatores interferem para que essa condição seja satisfeita, tais como a escolha fonte de radiação, a postura do paciente, a geometria de incidência, a distância de tratamento, a combinação de campos, entre outros. Para analisar a maneira como esse fatores influenciam na distribuição da dose no corpo, neste trabalho foram simulados computacionalmente cenários de Irradiação de Corpo Inteiro, que utilizam unidades de telecobaltoterapia e aceleradores lineares de 6 MV, para a estimativa da doses equivalente e efetiva utilizando o código de transporte de radiação MCNPX e os simuladores antropomórficos híbridos UFHADF e UFHADM nas posturas sentada, para irradiações RLAT e LLAT, e deitada para as projeções AP e PA. Para a validação dos espectros utilizados nas simulações foi calculada a PDP para a comparação com medidas experimentais. Já para a validação dos cenários de TBI foram estimadas as taxas de dose de entrada na pele também para a comparação com medidas experimentais. As curvas de PDP se mostraram de acordo com a literatura. Os valores das taxas de dose estimadas apresentaram uma diferença relativa menor que 10% em relação às medidas experimentais, o que permitiu estimar a dose nos órgãos. Os resultados das simulações mostram que as irradiações laterais dos simuladores UF na postura sentada oferecem uma distribuição de dose menos uniforme se comparado às irradiações AP/PA com o simulador na postura deitada. Para a geometria de irradiação PA a dose absorvida na medula vermelha é aproximadamente 20% maior que na projeção AP, o que sugere que o primeiro caso seja mais adequado para a destruição da medula doente. Quanto ao uso de objetos compensadores para atenuação da radiação no pulmão houve uma redução da dose absorvida por esse órgão em 23%, o que mostra sua eficácia e importância para esses procedimentos. Também foi observado que a diminuição da distância de tratamento do paciente a fonte de radiação e das paredes da sala leva a um aumento próximo de 10% e de 5%, respectivamente, na dose absorvida, o que sugere que sejam mais adequados tratamentos realizados a grandes distâncias foco-superfície e distantes das paredes da sala. Quanto à energia do feixe utilizado para Irradiação de Corpo Inteiro, as diferenças mais significativas entre o Cobalto-60 e o espectro do acelerador linear de 6 MV foram de até 46,23%, o que ocorreu para a geometria de irradiação PA, onde é observado que o primeiro deposita a maior parte de sua energia próximo a superfície, o que mostra que feixes mais energéticos são mais eficazes para irradiação em profundidades maiores. Outro fator analisado foi a combinação de campos adjacentes e sobrepostos para o tratamento, o que levou a superdosagens em alguns órgãos e comprometeu a uniformidade da dose assim como observado por outros autores. Os cálculos da dose efetiva permitiram concluir que há um maior comprometimento geral do corpo para irradiações na geometria de incidência LLAT. Também foi encontrado que a dose efetiva é superior na projeção AP que em PA assim como encontrado na literatura. As análises feitas mostram a importância e sugerem um estudo mais detalhado das condições de exposição para o planejamento de tratamentos por TBI.

Urychlovačem řízené podkritické systémy (ADS) se schopností transmutovat dlouhodobě žijící radionuklidy mohou vyřešit problematiku použitého jaderného paliva z aktuálních jaderných reaktorů. Stejně tak i potenciální problém s nedostatkem dnes používaného paliva, U-235, jelikož jsou schopny energeticky využít U-238 nebo i hojný izotop thoria Th-232. Tato disertační práce se v rámci základního ADS výzkumu zabývá spalačními reakcemi a produkcí tepla různých experimentálních terčů. Experimentální měření bylo provedeno ve Spojeném ústavu jaderných výzkumů v Dubně v Ruské federaci. V rámci doktorského studia bylo v průběhu let 2015-2019 provedeno 13 experimentů. Během výzkumu byly na urychlovači Fázotron ozařovány různé terče protony s energií 660 MeV. Nejdříve spalační terč QUINTA složený z 512 kg přírodního uranu, následně pak experimentální terče z olova a uhlíku nebo terč složený z olověných cihel. Byl proveden také speciální experiment zaměřený na detailní výzkum dvou protony ozařovaných uranových válečků, z nichž je složen spalační terč QUINTA. Výzkum byl především zaměřen na monitorování uvolňovaného tepla ze zpomalovaných protonů, spalační reakce a štěpení, způsobeného neutrony produkovanými spalační reakcí. Dále se na uvolňování tepla podílely piony a fotony. Teplota byla experimentálně měřena pomocí přesných termočlánků se speciální kalibrací. Rozdíly teplot byly monitorovány jak na povrchu, tak uvnitř terčů. Další výzkum byl zaměřený na monitorování unikajících neutronů z terče porovnávací metodou mezi dvěma detektory. První obsahoval malé množství štěpného materiálu s teplotním čidlem. Druhý byl složený z neštěpného materiálu (W nebo Ta), avšak s podobnými materiálovými vlastnostmi se stejnými rozměry. Unik neutronů (resp. neutronový tok mimo experimentální terč) byl detekován uvolněnou energií ze štěpné reakce. Tato práce se zabývá přesným měřením změny teploty pomocí termočlánků, s využitím elekroniky od National Instrument a softwaru LabView pro sběr dat. Pro práci s daty, analýzu a vizualizaci dat byl použit skriptovací jazyk Python 3.7. (s využitím několika knihoven). Přenos částic by simulován pomocí MCNPX 2.7.0., a konečně simulace přenosu tepla a určení povrchové teploty simulovaného modelu bylo provedeno v programu ANSYS Fluent (pro jednodušší výpočty ANSYS Transient Thermal).

Proton therapy is a relatively new treatment modality for cancer, having recently been incorporated into hospitals in the last two decades. Although proton therapy has much higher start up and treatment costs than traditional methods of radiotherapy, it continues to expand in use today. One reason for this is that proton therapy has the advantage of a more precise localization of dose compared to traditional radiotherapy. Other proposed advantages of proton therapy in the treatment of cancer may lead to a faster expanse in its use if proven to be more effective than traditional radiotherapy. Therefore, much research must be done to investigate the possible negative and positive effects of using proton therapy as a treatment modality. In proton therapy, protons do account for the vast majority of dose. However, when protons travel through matter, secondary particles are created by the interactions of protons and matter en route to and within the patient. It is believed that secondary dose can lead to secondary cancer, especially in pediatric cases. Therefore, the focus of this work is determining both primary and secondary dose. In order to develop relevant simulations, the specifications of the treatment room and beam were based off of real-world facilities as closely as possible. Using available data from proton accelerators and clinical facilities, an accurate proton therapy nozzle was designed. Dose calculations were performed by MCNPX using a simple water phantom, and then beam characteristics were investigated to ensure the accuracy of the model. After validation of the beam nozzle, primary and secondary dose values were tabulated and discussed. By demonstrating the method of these calculations, the purpose of this work is to serve as a guide into the relatively recent field of Monte Carlo methods in proton therapy.

This master’s thesis deals with usage of burn-up (spent) nuclear fuel in nuclear power plants of next generation – accelerator driven transmutation plants which is produced in current nuclear power plants. This system could significantly reduce the volume of dangerous long-lived radioisotopes and moreover they would be able to take advantage of its great energy potential due to fast neutron spectrum. In the introduction are listed basic knowledge and aspects of spent nuclear fuel along with its reprocessing and the possibility of further use while minimizing environmental impact. As another point detailed description of accelerator driven systems is described together with its basic components. In addition this search is followed by individual chronological enumeration of projects of global significance concerning their current development. Emphasis is placed on SAD and MYRRHA projects, which are used like base for calculations. This last, computational part, deals with the creation of the geometry of subcritical transmutation reactor driven by accelerator and subsequent evaluation which assembly is the most effective for transmutation and energy purposes along with changing of target, nuclear fuel and coolant/moderator.