Measurement of absolute γ-ray emission probabilities in the decay of 227Ac in equilibrium with its progeny

Abstract The 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

measurement of absolute γ ray emission probabilities in the decay of 235u

Abstract Accurate 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

Ionising radiation metrology for the metallurgical industry

Every 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.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Preparazione e certificazione di soluzioni di taratura monoalimentari

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Measurement of absolute γ-ray emission probabilities in the decay of 227Ac in equilibrium with its progeny

The 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 disks 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-emission probabilities are proposed.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Experimental and Monte Carlo simulation on new manganese bath facility for absolute neutron source emission rate measurement at ENEA-INMRI

This 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