[en] The enrichment of ²³⁵U in UO₂ pellets samples through the instrumental neutron activation analysis method (I.N.A.A.) was determined. By high resolution gamma-ray spectrometry (H.R.G.S.), from analysis of isotopic ratios between fission products peaks from ²³⁵U and ²³⁹Np different energies peaks from ²³⁸U, the enrichment was achieved. The 'Boatstrap' statistics technique for the analytical results, which is based in shaping results of an unknown distribution to the Gaussian distribution by B replications in interested statistics such as: the mean and its standard error, was introduced. (M.J.C.)

[en] Published in summary form only

[en] Published in summary form only

[en] The reference source method associated with HPGe γ-ray spectrometric techniques has been applied to half-life determinations of radionuclides used in nuclear medicine. Simultaneous measurements were undertaken for radiopharmaceutical nuclides such as ⁶⁷Ga, ⁹⁹Tc^m, ¹²³I, ¹³¹I and another radionuclide as reference. Besides optimizing the analysis time, this procedure was shown to be independent of the instrumental technique, environmental and radiochemical impurity interferences for most radionuclides. However, some restrictions were observed in samples that contained impurities with the same emission energy or an energy that was very close to the energy of the radionuclide to be measured. The measurement conditions improved the quoted accuracy of the half-life by reducing the type B component uncertainty

[en] Published in summary form only

[en] The determination of ²³⁵U by non-destructive assay of gamma spectrometry can be made with SAM-2 portable equipment and NaI (T1) cintillation detector, model RD-19, from Eberline. This has been implanted by CNEN's Safeguards Laboratory for routine inspections. The first measurements were carried out in the Fuel Fabricaton Plant, at Resende. The ranges of 0.7-1.9% for the precision and a relative error of 0.02-1.1% were obtained in the CNEN's Safeguards Laboratory, when applied to UO₂-pellets enriched at 3.3% 235U. The ranges of 11-15% for the precision and a relative error of 12-14% for fuel rods with 0.22% of enrichment, and 0.5-1.8% for the precision and relative error of 0.5-1.0% for fuel rods with 3.3% of ²³⁵U, were obtained by this technique. (Author)

[en] Published in summary form only

[en] The National Laboratory for Ionizing Radiation Metrology (LNMRI/IRD/CNEN) of Rio de Janeiro performed standardization of different radionuclides. Such standards are applied in nuclear industries, nuclear research, radiation protection and nuclear medicine. The comparative method using a Ge detector was applied for obtaining results of some radioactive point and ampoule sources. The activities of ²²Na, ⁶⁰Co, ¹³³Ba and ¹³⁷Cs radionuclides were determined. The total uncertainties reached values below 1.0 % to liquid samples and below 1.4% to solid samples, in a confidence level of 68 %. (author)

[en] The Instrumental Neutron Activation Analysis (I.N.A.A.) where the U-235 quantity was determined in UO₂ pellets, were compared with the Neutron Coincidence Collor (N.C.C.) results. The I.N.A.A. is based in a sample activation by thermal neutrons, I.E.A. - R1 reactor, I.P.E.N., S.P., to obtain different fission products. The high resolution gamma spectrometry (H.R.G.S.) was applied to determining elements quantity. The enrichment was obtained through the ratios between different peaks from U-238 and U-238 decays after irradiation. These results were verified and they were bellow compared with the N.C.C. analysis. The relative error was -2.7%

[en] Radionuclide metrology laboratories aim to provide radioactive standards for detector calibrations in nuclear safety areas with low uncertainties. Such standards are applied in nuclear industries, according to the requirements of monitoring programmes. The standard radionuclides of ¹³³Ba, ¹⁵²Eu and ^166mHo are suitable to the determination of efficiency curves in HPGe detectors due to their multi-gamma emissions, which are intense and well separate in the spectrum. With efficiency curves it is possible to do the measurements without needing to use standards. In this work was made a verifying of the uncertainties obtained for the two relative methods: comparative (sample-standard) and efficiency curve. The total uncertainties obtained by sample-standard method varied from 0.4 to 1.2 % (k=1). The results using efficiency curve method are between 0.9 to 2.2 % (k=1). (author)