A new system has been designed to automatically load the samples to be irradiated at the gamma irradiation facility of the Nuclear Technology Development Centre (CDTN) at Belo Horizonte, Brazil. The objective of this system is the optimization of the experiments performed at the Gamma Irradiation Laboratory for short-time irradiations without interruption of the irradiator cycles. The installation of this new system requires the opening of a hole at the labyrinth door to allow the loading of irradiating products. Due to this alteration on the original design, the door opening into the labyrinth requires shielding verification. The dose rate with the door open is calculated using Monte Carlo MCNPX v 2.6.0 code. The Monte Carlo source simulations were validated with experimental measurements of dose rate. The simulation demonstrated that a hole can be opened at the labyrinth entrance when installing an automatic loading system. Not only does it comply with dose constraint requirements, but it also complies with national and international standards.
Abstract. The laser flash method is based on measuring the temperature transient. The effect of the thermal inertia of the temperature measurement system is not negligible and cannot be ignored due to the fast dynamics of the measured thermal transient. This paper presents the new infrared radiation temperature measurement system applied to the thermal diffusivity measurements based on the laser flash method. The developed system consists in a detector cooled in liquid nitrogen, collimating lenses and a mathematical modeling developed in LabView. As a result, the generated electrical signal is converted into temperature. A detailed description of this new temperature measurement system is presented, as well as its mathematical model, computational implementation and calibration. For validate the new system, reference samples of homogeneous materials (Pyroceram 9606 and Inconel 600) were tested and the results of thermal diffusivities were compared with its reference certificates. The thermal diffusivity values measured by using the new system are in agreement with reference values, with less than 2 % of relative deviation.
IntroductionThe determination of thermal diffusivity by laser flash method [1-4] is based on the variation of temperature on the opposite side of a thin cylindrical sample resulting from a short pulse of radiant energy received on its front side. This thermogram is measured and the thermal diffusivity is calculated as a function of sample thickness and the time required to reach half of the maximum rate of temperature on the opposite side. The Laboratório de Medição de Propriedades termofísicas (LMPT) of the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN) is expanding the measurement capabilities of its metrological platform devoted to the determination of the main thermophysical properties of materials. Then, the development of new temperature measurement system with a response time of nanoseconds is a priority to improve the quality of the thermal diffusivity measurement of materials. The new temperature measurement system was designed and built to improve experimental apparatus used to determined thermal diffusivity. The mathematical modelling of this system is also presented on this paper as well as its computational implementation and calibration. Reference samples of homogeneous materials (Pyroceram 9606 and Inconel 600) were
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