45 research outputs found
Measurement of absolute γ-ray emission probabilities in the decay of 227Ac in equilibrium with its progeny
No full textThe emission probabilities of γ rays produced in the 227Ac decay series were determined by high-resolution γ-ray spectrometry of sources with standardised activity. The sources were prepared quantitatively on glass discs by drop deposition of a solution with 227Ac in radioactive equilibrium with its daughter nuclides. Their activity was measured by a primary standardisation technique based on alpha-particle counting at a defined low solid angle. Four laboratories performed γ-ray spectrometry and derived absolute γ-ray intensities. Mean values were calculated and compared with literature data and the currently recommended evaluated data. New values on certain γ-ray emission probabilities are proposed. © 2018 The Author
Measurement of absolute γ-ray emission probabilities in the decay of 235U
No full textAccurate measurements were performed of the photon emission probabilities following the α decay of 235U to 231Th. Sources of highly enriched 235U were characterised in terms of isotopic composition by mass spectrometry and their activities were standardised by means of alpha-particle counting at a low defined solid angle. The standardised sources were subsequently measured by high-resolution γ-ray spectrometry with calibrated high-purity germanium detectors to determine the photon emission probabilities. Four laboratories participated in this work and reported emission probabilities for 33 γ-ray lines. Most of them agree with previously published evaluated data. In addition, new values are proposed for γ-lines which have been measured only once in the past. © 2017 The Author
Production and characterization of 228Th calibration sources with low neutron emission for GERDA
No full textThe GERDA experiment at the Laboratori Nazionali del Gran Sasso (LNGS) searches for the neutrinoless double beta decay of 76Ge. In view of the GERDA Phase II data collection, four new 228Th radioactive sources for the calibration of the germanium detectors enriched in 76Ge have been produced with a new technique, leading to a reduced neutron emission rate from (α, n) reactions. The gamma activities of the sources were determined with a total uncertainty of ∼4% using an ultra-low background HPGe detector operated underground at LNGS. The neutron emission rate was determined using a low background LiI(Eu) detector and a 3He counter at LNGS. In both cases, the measured neutron activity is ∼10-6 n/(sc·Bq), with a reduction of about one order of magnitude with respect to commercially available 228Th sources. Additionally, a specific leak test with a sensitivity to leaks down to ∼10 mBq was developed to investigate the tightness of the stainless steel capsules housing the sources after their use in cryogenic environment. © 2015 IOP Publishing Ltd and Sissa Medialab srl
Geometric features of gerotor pumps: Analytic vs CAD methods
No full textAccurate simulation models of gerotor pumps require knowledge of geometric features of these units. Instantaneous volumes of chambers as well as their volume derivatives lead to kinematic flow rate, flow ripple index, displacement. Flow passage areas between a chamber and the inlet/delivery volumes during a complete shaft revolution also need to be known. General analytical methods (integral-derivative and derivative-integral) have been developed for the calculation of geometric quantities of gear as well as vane pumps and will be reported in the paper with specific emphasis on gerotor units. The approach leading to these geometric informations has traditionally been grounded on a 2D analysis of involved features. However, in the last decade, there has been a progressive and relentless development and use of 3D CAD software that has led to the possibility of having at hand a virtual representation of these positive displacement machines. Accordingly, a novel method that requires the 3D model of the gerotor pump is presented and the paper demonstrates how geometric features of the unit can be obtained. Main characteristics of this methodology are the use of parametric relations that define the relative position of the rotating gears, and the use of virtual components. A validation of this proposed approach is discussed contrasting analytic and CAD-model based outcomes. This methodology has been successful also in axial piston machines as well as for the determination of flow passage areas of complex proportional direction spool valve
Activity measurements of the radionuclide 99mTc for the VNIIM, Russian Federation and ENEA-INMRI, Italy, in the ongoing comparison BIPM.RI(II)-K4.Tc-99m and KCRV update in the BIPM.RI(II)-K1.Tc-99m comparison
No full textIn 2014, comparisons of activity measurements of 99mTc using the Transfer Instrument of the International Reference System (SIRTI) took place at the VNIIM (Russian Federation) and at the ENEA-INMRI (Italy), with comparison identifier BIPM.RI(II)-K4.Tc-99m. Ampoules containing about 32 kBq of 99mTc solutions were measured in the SIRTI for three half-lives. There are now nine results in the BIPM.RI(II)-K4.Tc-99m comparison. This comparison is linked to the BIPM.RI(II)-K1.Tc-99m comparison and the key comparison reference value (KCRV) of the BIPM.RI(II)-K1.Tc-99m has been updated to include eligible results from BIPM.RI(II)-K4.Tc-99m. The degrees of equivalence between each equivalent activity measured in the SIR or the SIRTI and the KCRV have been calculated and the results are given in the form of a table. A graphical presentation is also given
18F primary standard at ENEA-INMRI by three absolute techniques and calibration of a well-type IG11 ionization chamber
No full textA new 18F primary standardization carried out at ENEA-INMRI by three different absolute techniques, i.e. 4πγNaI(Tl)γ high-efficiency counting, TDCR and 4πβ(LS)-γ[NaI(Tl)] coincidence counting method, allowed the calibration of a fixed well-reentrant IG11 ionization chamber (IC), with an uncertainty lower than 1%, and to check the calibration factor of a portable well-type IC NPL-CRC model, previously calibrated. By the new standard the ENEA-INMRI was linked to the BIPM International Reference System (SIR) through the BIPM SIR Transfer Instrument (SIRTI). © 2016 Elsevier Ltd
Ionising radiation metrology for the metallurgical industry
No full textEvery year millions tons of steel are produced worldwide from recycled scrap loads. Although the detection systems in the steelworks prevent most orphan radioactive sources from entering the furnace, there is still the possibility of accidentally melting a radioactive source. The MetroMetal project, carried out in the frame of the European Metrology Research Programme (EMRP), addresses this problem by studying the existing measurement systems, developing sets of reference sources in various matrices (cast steel, slag, fume dust) and proposing new detection instruments. This paper presents the key lines of the project and describes the preparation of radioactive sources as well as the intercomparison exercises used to test the calibration and correction methods proposed within the project
Le ceramiche a vernice nera nel IV e III secolo a.C. dell’Ager Portuensis e di Ostia: notizie preliminari sulle ricerche archeologiche e archeometriche
No full textCharacterization and calibration of a novel detection system for real time monitoring of radioactive contamination in water processed at water treatment facilities
No full textExperimental and Monte Carlo simulation on new manganese bath facility for absolute neutron source emission rate measurement at ENEA-INMRI
No full textThis work deals with the absolute measurement of the neutron emission rate from a Am-241-Be source by means of the manganese sulphate bath technique, which is the principal method for the absolute determination of the neutron emission rate from radionuclide neutron sources. The facility consists of a spherical container filled with an aqueous solution of manganese sulphate with a Am-241-Be neutron source placed at the center. As well known, neutrons from the source, after having been thermalized by the aqueous solution, undergo neutron capture by hydrogen, manganese, sulphur, and oxygen nuclei, thus inducing a certain activity to the solution. Subsequent gamma spectrometry measurements of Mn-56 activity generated by Mn-55 neutron activation allows to determine the neutron emission rate of the source, The experimental activity has involved a variety of measurement techniques and calculation procedures, ranging from neutron reactor activation to liquid scintillation counting and Monte Carlo calculations. Neutron activations of Mn-55 samples has been carried out with the TRIGA reactor of the ENEA-Casaccia Research Centre, and Mn-56 activated samples were subsequently characterized by liquid scintillation counting, in order to obtain reference standards for the calibration of the NaI(Tl) scintillation detectors utilized to record gamma-ray emission from Mn-56. Monte Carlo calculations, carried out by the MCNPX code, were required to calculate neutron transport within the sulphate manganese bath, in particular to determine Mn-55 neutron capture probability, and (n, alpha) and (n, p) concurrent reactions, as well as the neutron leakage. Such a procedure has allowed to maintaining the neutron emission rate uncertainty well below 1 %. All the measurements have been carried out at the ENEA-Casaccia Research Centre by the Italian National Institute of Ionizing Radiation Metrology
