[en] The present consideration of the systematic residuals which emerge when Uranus and Neptune observations are compared to their theories will proceed from the supposition that these discrepancies are due to an unknown 'planet X'. An effort is accordingly made to ascertain the ideal region, rather than a specific position or positions, in which the existence of such a planet will account for the systematic residuals. The problematic relationship of the probable albedo of a planet X to the mass it must possess, in view of the present calculations, is assessed. 5 refs

[en] A general procedure of easy implementation which was validated with ¹³³Ba nuclear data to the technique of gamma-ray spectrometry with HPGe detectors or NaI (Tl) was developed in order to ensure the quality of the radionuclide analysis. This procedure can be applied to: environmental monitoring programs with air filter samples, water, soil and sediment; NORM and TENORM materials; identification of fission products; nuclear safeguards; neutron activation; or nuclear medicine. It was developed the calculation routine to determine the activity of gamma sources, emission probabilities of photons and half-lives or even identify radionuclidic impurity, as well as assess their associated uncertainties. (author)

[en] There are few radionuclides with high intensity gamma rays and well distributed in the energy spectrum in the range of 117 to 465 keV to be used as a standard. These energies are fundamental for the accurate knowledge of the activity of radiopharmaceuticals used in nuclear medicine. The National Ionizing Radiation Metrology Laboratory (LNMRI/IRD/CNEN) seeks to identify radionuclides that have the potential to be used as a reference standard due to their long half-life and their emission spectrum. In this way, the LNMRI promotes studies of new radionuclides that can be standardized. The ²²'9Th, with its well-defined energies and intensities, emerges as an alternative standard for calibrating the efficiency of germanium detectors for gamma spectrometry. Here the ²²⁹Th was preliminarily standardized by the anticoincidence counting method 4παβ (LS) γ (NaI (Tl)). The emission probabilities of the main lines of the ²²⁹Th were determined by high-resolution gamma spectrometry with good precision. The results show a good agreement with the literature data, which can be used as a radioactive standard

[en] We calculate the hydrodynamical expansion of a hot nucleus. The results indicate that at breakup the excited nuclear system emits its surface region with a relatively high kinetic energy

No abstract available

[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)

[en] From a commercial supplier a solution containing ²²⁶Ra has been standardized at National Laboratory for Ionizing Radiation Metrology (LNMRI) for the first time using Liquid scintillation based measurement. The measurement methods are 4παβ-γ live-timed anticoincidence counting. The results obtained by anticoincidence counting were adopted as reference value and its combined uncertainty was 0.94 %. The agreement of this reference value with reference system with ionization chamber was 0.56 %. This standardization was made in order to reduce the uncertainty in ²²⁶Ra measurement in Brazil. (author)

[en] In this article we will describe the radionuclide standardization system TDCR, Triple-to-Double Coincidence Ratio, of the National Metrology Laboratory of Ionizing Radiation and its stage of development to provide a method to standardize radionuclides difficult by other techniques. The TDCR is an absolute measurement method, therefore, it does not depend on a reference standard to determine the radioactive activity of the samples, initially developed to standardize radionuclides that decay by pure beta emission (electrons and positrons), such as ³H, ¹⁴C, ⁴⁵Ca and ⁶³Ni and electronic capture, such as the ⁵⁵Fe. However, it is possible to standardize alpha emitters, such as ²⁴¹Am, and other radionuclides with a complex decay scheme. The method uses three photomultiplier tubes aligned at an angle of 120° to each other, and double and triple coincidences between the three photomultiplier tubes are collected. The method is currently used in 26 radionuclide metrology laboratories around the world. In this article we also present the radionuclides that will be standardized by the method. (author)

No abstract available

No abstract available