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 identification of the occurrence of 232Th, by measuring the energies of the children radioisotopes 228Ac, 208Tl, 212 Bi and 212Pb, in their places of origin, using the Mobile Lab for Identification of Radiological and Nuclear Agents - LabMovelRN, by discriminating their environmental concentration normal and NORM [1] is important for the performance of the operational teams of the Brazilian Army Chemical, Biological, Radiological and Nuclear Defense Institute (IDQBRN), optimizing their time of action, and reducing the chain of custody of the sample. Due to the operational difficulty of using HPGe detectors in LabMovelRN, an adaptation is being carried out in the laboratory in order to allow the analysis of 232Th in soil samples by the gamma spectrometry technique using scintillation detectors [2] of NaI (Tl) type well as the characterization of the response of this scintillator detector in energy, resolution and energy efficiency up to 3,000 keV.
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