Neinei -- The Neutron Imaging Center at the Brazilian Multipurpose Reactor

Neutron imaging is a non-destructive technique for analyzing a wide class of materials, such as archaeological or structures of industrial materials. Technological advances, in recent decades, have had a great impact on the neutron imaging technique, evolving from simple radiographs using films (2D) to modern tomography systems with digital processing (3D). The Instituto de Pesquisas Energ\'eticas e Nucleares (IPEN), in Brazil, houses a 5MW research nuclear reactor, called IEA-R1, where there is a neutron imaging instrument located at the beam hole 08 (BH08) with $1.0 \times 10^{6}$ $n/cm^{2}s$ in the sample position. IEA-R1 is over 60 years old and the future of neutron science in Brazil, including imaging, will be expanded on a new facility called the Brazilian Multipurpose Reactor (RMB). The RMB will house a suite of instruments at the Neutron National Laboratory, including the neutron imaging facility called Neinei. Inspired by recent work, we have calculated the thermal neutron flux at the sample position, using the Monte Carlo method, in the Neinei and compared it to the results obtained with the Neutra (PSI), Antares (FRM II), BT2 (NIST) and DINGO (OPAL) instruments. The results are promising and provide avenues for future improvements.Comment: 8 pages, 9 figures. Preprin

Simulating Araponga - The High-Resolution Diffractometer of Brazilian Multipurpose Reactor

The Brazilian Multipurpose Reactor (RMB) is a fundamental project that aims to turn Brazil into a self-sufficient country in the production of radioisotopes and radiopharmaceuticals to supply the Unified Health System (SUS) as much as the private institutions. In addition, the RMB project describes other applications as irradiation and testing of nuclear fuels and structural material analysis, for instance. There are many techniques in the project to study structural aspects of materials, where neutron diffraction represents one of the priorities for implementation. This technique will take place mainly on two diffractometers on Thermal Neutron Guide 1 (TG1), namely Araponga, a high-resolution diffractometer, and Flautim, a high-intensity diffractometer. In this work, we study the performance of the Araponga diffractometer through McStas simulations with input produced by the MCNP code of the RMB core. We investigate the neutron flux values considering a state-of-art high-resolution diffractometer, and the results are promising since some simulated scenarios present values compatible with high-intensity devices

Utilização da braquiterapia com folhas de ouro (Au198) em tumor de pele de cão

This study showed a skin squamous cell carcinoma clinical case from 8-years-old female weimaranner, treated by gold-198 foil brachytherapy. The aims were to evaluate special radioactive mould performed to be used on Veterinary practioners and, it's efficiency on one case of skin tumor treatment in dog. The method showed efficacy on the skin tumor treatment and radiological protection especially for the professional team involved, low cost and better radiobiological results when it was compared with standard treatment using others radioactive elements.Este trabalho relata um caso clínico de carcinoma escamo celular cutâneo em um cão da raça Weimaraner, fêmea, 8 anos de idade tratado utilizando-se braquiterapia com folhas de Ouro-198. Os objetivos deste relato foram: avaliar o uso de um molde radioativo confeccionado para uso veterinário e sua eficácia no tratamento de um tumor de pele em cão. O método demonstrou ser eficaz no tratamento do tumor, mostrou ser uma prática segura para a equipe profissional envolvida, com baixos custos e resultado radiobiológico superior quando comparado com o tratamento padrão utilizado com outros elementos radioativos

REACTOR NOISE EXPERIMENTS CONSIDERING HIGH FREQUENCIES IN THE IPEN/MB-01 REACTOR

Reactor noise experiments at high frequencies (up to 100 kHz) in subcritical configurations have been performed at the IPEN/MB-01 research reactor facility. The core configuration considered a short version of the IPEN/MB-01 core in a 24 × 26 rectangular array of fuel rods. The subcritical configurations considered the control banks totally withdrawn and the moderator poisoned with H3BO3. The boron concentrations were: 286.8 ± 10 and 578.6 ± 10 ppm. The pulses of two 3He detectors in the reflector region were summed and inserted into the IPEN/MB-01 Correlator and the APSD (Auto Power Spectral Density) was inferred through a mathematical model. The analysis reveals that the APSD in this frequency range is best described by a four-mode decay model. According to the two-region two-group (thermal and fast) kinetic model developed in this work, the first two decay modes describe the thermal group and the other two describe the fast group. After a tedious and severe analyses of the least-square fit of the experimental data, it was concluded that the kinetic behavior of the thermal and fast neutrons can be considered uncoupled. The analysis of the experimental data is still in progress and only the thermal group of the case of 286.8 ppm of boron was analyzed and some parameters could be inferred. The most important one so far is the prompt neutron generation time in the core region that could be inferred with a good level of accuracy

Numerical analysis of an incremented statistical sampling procedure in MCNP

MCNP has stood so far as one of the main Monte Carlo radiation transport codes. Its use, as any other Monte Carlo based code, has increased as computers perform calculations faster and become more affordable along time. However, the use of Monte Carlo method to tally events in volumes which represent a small fraction of the whole system may turn to be unfeasible, if a straight analogue transport procedure (no use of variance reduction techniques) is employed and precise results are demanded. Calculations of reaction rates in activation foils placed in critical systems turn to be one of the mentioned cases. The present work takes advantage of the fixed source representation from MCNP to perform the above mentioned task in a more effective sampling way (characterizing neutron population in the vicinity of the tallying region and using it in a geometric reduced coupled simulation). An extended analysis of source dependent parameters is studied in order to understand their influence on simulation performance and on validity of results. Although discrepant results have been observed for small enveloping regions, the procedure presents itself as very efficient, giving adequate and precise results in shorter times than the standard analogue procedure. (C) 2007 Elsevier Ltd. All rights reserved

Utilização do código Monte Carlo N-Particle Extended (MCNPX) para discriminar a dose de radiação absorvida nas diferentes regiões e restaurações dentárias

Os tumores da região da cabeça e pescoço correspondem a 14.000 casos novos (INCA 2010). O tratamento para esse tipo de doença é a cirurgia seguida de radioterapia e quimioterapia. Durante a realização da radioterapia com feixes externos, o paciente é submetido à radiação em um volume alvo que corresponde à grande parte da cavidade bucal, atingindo as glândulas salivares e toda a arcada dentária, causando vários efeitos secundários. O trabalho utilizou o MCNPX para cálculo de dose de radiação absorvida, pelas diferentes regiões do dente e para materiais utilizados em restaurações dentárias, quando estes são submetidos a diferentes feixes de radiação simulando pacientes que estão em tratamento radioterápico na região da cabeça e pescoço. Os espectros dos feixes de raios X de megavoltagem simulados com o Método MCNPX apresentam região de equilíbrio eletrônico em 1,5cm (6MV) e 2,4cm (10MV); como a região do esmalte do dente está a uma profundidade da pele da face (entrada do campo de radiação) maior que esses valores, é natural de se esperar que a região mais externa do dente (esmalte) absorva maior dose que as regiões mais internas. Quando se pensa na modelagem do dente isoladamente (feixe de radiação diretamente no dente), também se espera que a região mais externa absorva maior dose, devido à dimensão total do dente, frente à espessura da região de equilíbrio eletrônico, além das características e dureza dessa região. Esses conceitos são reforçados com os resultados obtidos com o MCNPX

Gold (198Au) foils brachytherapy use on canine skin tumor

Este trabalho relata um caso clínico de carcinoma escamo celular cutâneo em um cão da raça Weimaraner, fêmea, 8 anos de idade tratado utilizando-se braquiterapia com folhas de Ouro-198. Os objetivos deste relato foram: avaliar o uso de um molde radioativo confeccionado para uso veterinário e sua eficácia no tratamento de um tumor de pele em cão. O método demonstrou ser eficaz no tratamento do tumor, mostrou ser uma prática segura para a equipe profissional envolvida, com baixos custos e resultado radiobiológico superior quando comparado com o tratamento padrão utilizado com outros elementos radioativos