Este trabalho descreve a modelagem computacional de dispersão atmosférica decorrente de acidente radiológico hipotético em reator modular de pequeno porte (SMR), cuja potência é de 16 MWe (50 MWt). Utilizou-se o software SCALE para modelar o núcleo com três regiões de enriquecimento do combustível, a 4%, 5% e 20%, e obter atividades dos radionuclídeos oriundos de reações nucleares durante o burnup, após 2 anos de operação. Foi escolhida uma localidade de interior para instalação do SMR, onde informações sobre condições meteorológicas foram coletadas para identificação da classe de estabilidade atmosférica predominante. Dentre os radionuclídeos do inventário, considerou-se a contribuição do Cs-137 para simulação, usando-se o código HotSpot, da concentração e das doses totais efetivas (TEDE) recebidas, ambas em função da distância do evento. Os resultados sugerem que a TEDE máxima calculada foi de 3,6 Sv, a 34 m do reator, diminuindo com o tempo e distância, e seguindo o modelo Gaussiano de dispersão, e que a pluma de contaminação é dependente dos critérios de Pasquill-Gifford e da atividade do Cs-137. Para doses entre 1 mSv e 10 mSv e entre 10 mSv e 50 mSv, sugere-se a abrigagem da população nas construções existentes na localidade, e para valores acima de 50 mSv, a abrigagem nessas condições ou a evacuação do pessoal das proximidades do reator em movimento contrário ao de propagação da pluma. A relevância dessa investigação mostra a importância do planejamento de respostas em situação de emergência e a influência das condições meteorológicas, considerando-se os dados assumidos na

For designing a shielding, it is necessary, mainly, to determine or have access to the following parameters: transmission factors of the material used and type of radiation to be shielded. Cylindrical test specimens with different thicknesses were developed for experimentally obtaining the material transmission factor for shielding calculation. The cylindrical test specimens were made considering the geometric characteristics of the detector, the ease of production and the energy of 0.511 MeV from the 18 F-FDG decay. A type of concrete widely used in Brazil was used in the preparation of the cylindrical test specimens.

This study establishes a quantitative analysis protocol of radionuclides in a radiological and nuclear mobile laboratory of the Brazilian Army's Institute of Chemical, Biological, Radiological and Nuclear Defense. The gamma spectrometry technique was used, by a HPGe detector, to identify certified gamma-emitting radioactive sources (Am-241, Cs-137 and Co-60) present in a standard solution diluted in a Marinelli flask of 4L. Energy, resolution and efficiency calibration curves were determined using the LabFit software, for this detector, in the considered geometry. The results show to be satisfactory the linear adjustment (Channel versus Energy) of set points have been obtained experimentally which was confirmed by the determination coefficient achieved (). Besides that, it could be also verified that the exponential function was the mathematical model that best represented the answer of the HPGe detector energy resolution and that the mathematical adjustment options provided by LabFit which allowed to correlate the counting efficiency with the energy of each photopeak, despite the lack of a greater amount of energy. To define specific activities, the measurement errors between theoretical and experimental values were less than 4%, evidencing the reasonable responsiveness of the measurement system.

This study analyses the ambient dose equivalent around transmission full-body scanners used in Brazilian prisons and airports. In order to achieve this goal, three transmission full-body scanners of the same model assembled by a Brazilian manufacturer were evaluated. Ambient dose equivalent rates were measured at several positions around these screening devices with the help of an ionisation chamber made by Ludlum, model 9DP. These systems consist of an X-ray generator with three distinct modes of operation, each with a unique value for maximum energy (100, 150 and 160 keV) and current (0.4, 0.5 and 0.9 mA). Results show the integrated dose per scan at each of the measurement positions considered, presenting values for ambient dose equivalent with and without an individual being scanned, in order to take into account the scattering due to the presence of a human body.

The provision for the Brazilian Army of equipment that provides reliable and safe measurements, enabling decision-making based on radioprotection parameters, leads to the need to investigate the metrology of the calibration system used in the Radiation Monitor Calibration Laboratory (LabCal) of the Institute of Chemical, Biological, Radiological and Nuclear Defense (IDQBRN). To this end, the commissioning in cesium-137 is of primary importance in this process. In order to check the conformity of the radiator system, in this work, the ambient dose equivalent rate, , was obtained experimentally for several configurations to compare them with the appropriate theoretical concepts. For this, the distance between the source of Cesium-137 (36.9 GBq in 01/22/2015) and the ionization chamber was varied from 500 to 3000 mm at 250mm intervals. To obtain lower ambient dose equivalent rates, 15 and 32 mm thick lead attenuators were used. The mathematical model that best fit the experimental values was analyzed. In all cases, the potential function offers better fit, since the coefficients of determination obtained are approximately equal to 1, obeying the Law of the Inverse Square of the Distance, according to theoretical foundation. Moreover, it was evaluated that the relative deviations are below the limits established by the relevant standard.

The provision for the Brazilian Army of equipment that provides reliable and safe measurements leads to the need  for a metrology study of the calibration system used in the Institute's Radiation Monitor Calibration Laboratory (LabCal) of Chemical, Biological, Radiological and Nuclear Defense (IDQBRN). In order  to verify the stability of dosimetry in Cesium-137, the ambient dose equivalent rate, H*(10), was experimentally obtained for certain distance settings and lead attenuators at different dates in order to compare them. To this end, the distance between the source of Cesium-137 and the ionization chamber was varied from 1000, 2000 and 3000 mm without attenuator and with lead attenuators with 15 and 32 mm. In this work, the reproducibility of the system was analyzed by comparing the scenario of equal distance and attenuator, but with a different test date. For this purpose, the correction due to the radioactive decay of the source up to a reference date was used for comparison.Furthermore,the stability of the LabCal in Cesium-137 was verified in the light of the relevant standards for exposures without attenuators and with select attenuators for the tested distances.

The application of nuclear technologies in a cargo and container inspection facility can increase the risk of accidents. Estimating the radiation dose in the controlled area generates critical information for elaborating routines aimed at establishing more effective safety procedures. For radiological protection purposes, mapping ambient dose equivalent H*(10) levels is crucial. The radiation source used was a fixed linear accelerator of 4.5 MeV. Five RadEye PRD-ER (Thermo Fisher Scientific) personal radiation monitors and five Geiger-Müller MRAD 111 (Ultra Radac) personal radiation monitors were used for the radiation measurements. The highest ambient equivalent dose rate and dose per scan were found with the Geiger-Müller monitors at values of 5.76E-01 mSv/h and 1.12E-03 mSv, respectively. The results showed that for public individuals, the number of scans at the point of highest dose rate value cannot exceed 893-unit operations. Additionally, the risks involved in the abnormal situation (increased H*(10)) were estimated by using a model to predict the development of solid cancer as a result of occupational radiological exposure. This procedure highlights the risks involved, hence providing initial support to the decision process.

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