Romolo Remetti

Monte Carlo simulation and radiometric characterization of proton irradiated [18O]H2O for the treatment of the waste streams originated from [18F]FDG synthesis process

The aim of this work is quantifying the radionuclidic impurities of the irradiated [(18)O]water originated by the [(18)F]FDG synthesis process, and characterizing, from a radioprotection point of view, the waste streams produced. Two samples of 2.4ml [(18)O]H(2)O, contained in two different target cells, have been irradiated with a proton current of 37μA in a PETtrace cyclotron for about one hour each; after irradiation, without performing any chemical purification process but waiting only for the (18)F decay, they have been transferred in two vials and measured by HPGe gamma spectrometry and, subsequently, by Liquid Scintillation Counting. Previously, Monte Carlo calculations had been carried out in order to estimate the radionuclides generated within the target components ([(18)O]H(2)O, silver body and Havar® foil), with the aim to identify the nuclides expected to be found in the irradiated water. Experimental results for the two samples, normalized to the same irradiation time, show practically the same value of tritium concentration (about 36kBq/ml) while gamma emitters activity concentrations exhibit a greater spread. Considering that tritium derives from water activation while other pollutants are caused by activated cell materials released into water through erosion/corrosion mechanisms, such a spread is likely to be attributable to differences in the proton beam shape and position (production of different natural circulation patterns inside the target and different erosion mechanisms of the target cell walls). Both tritium and the other radioactive pollutants exhibit absolute values of activity and activity concentrations below the exemption limits set down in EURATOM Council Directive 96/29.

ABCD-Tool, a software suite for the analysis of α/β spectra from liquid scintillation counting

This paper presents the alpha/beta complete deconvolution tool (ABCD-Tool), a C++ application for the analysis of spectra from liquid scintillation counting (LSC) measurements. In addition to the basic algorithms for standard gross alpha/beta analysis and the determination of the counting efficiency, the software implements a recent unfolding technique based on Fourier transforms, which gives precise and reliable results even in the case of complex, strongly overlapping spectra. The application is designed to be used with alpha/beta spectra generated from Perkin Elmer Wallac Quantulus 1220. However, future upgrades are scheduled in order to extend the compatibility to spectra from other LSC instruments in commerce.

X-ray differential absorptiometry for Pb content evaluation in airborne dust

Abstract An experimental study has been conducted in order to assess the performance achievable with an instrument based on the method of x-ray differential absorptiometry aimed at the determination of the Pb content of standard aerosol sampling filters. The method, described here, relies on the transmission of photons of two energies, properly chosen in the 10–15 keV range. The principles and basic features of the instrumental approach are discussed on the basis of experimental data and an evaluation of the performances achievable is given.

Fast neutron-flux monitoring instrumentation for lead fast reactors: A preliminary study on fission chamber performances

Although Sodium Fast Reactors (SFRs) are the most investigated solutions for the future fast-flux facilities so far, Lead Fast Reactors (LFRs) promise to be a very competitive alternative thanks to their peculiarity concerning coolant-safety, fuel cycle and waste management.Nevertheless, the development of LFRs presents today some drawbacks still to be solved. Due to the harder neutron flux, the current instrumentation developed for SFRs is likely to be extended to LFRs as a first attempt. Otherwise, new monitoring instrumentation could be developed in order to assure more tailored results. Different measurement technologies can be considered for fast flux monitoring and flux absolute measurements in order to provide a reliable and quick calibration of the overall reactor neutron instrumentation. The goal of this paper is to study the validity of typical fast reactor fission chamber designs (e.g. SuperPhenix fission chambers), indicating which are the limitations when used in a LFR environment. Afterwards, alternative detector solutions with enhanced sensitivity and response will be proposed.Copyright

Experimental tests on the reduction of radon decay products’ unattached fraction in indoor environment and its influence on effective dose

The work studies the influence of how the unattached fraction of radon daughters can influence effective dose. An experimental work was carried out for measuring the unattached fraction in presence of different size aerosols, and for each test an estimate of the effective dose was given. Tests were carried out at fixed radon concentrations and with different size aerosols. Potential alpha energy concentrations of both total and free fractions were measured, together with radon and aerosols air concentrations. Results showed increments of the equilibrium factor, reduction of the unattached fraction, and decrease of the effective dose.

CONSIDERATIONS ON REDUCTION OF INDOOR AIR POLLUTION FROM RADIOACTIVE EMISSIONS FROM BUILDING MATERIALS AND THE GROUND

The goal of this paper is to study the reduction of health risks from indoor radioactive pollutants, as thoron emissions from common building materials, and radon emission from both building materials and the ground. In particular, when dealing with the indoor environment, one of the most important hazard is represented by radon gas, considered by the World Health Organization (WHO) as the second largest cause of lung cancer, cigarette smoke being the first. Such a radioactive gas belongs to the natural radioactive background of radiation, and its presence all over the world is unavoidable. Radon gas density varies due to microclimatic factors such as temperature, air pressure, humidity and changes in ground layers. Radon gas emerges from the ground and penetrates building basements, accumulating itself into the indoor air, and being breathed in by people. Taking care of the airtightness of windows allows the radon concentration to build up, in some cases beyond reference levels, together with other chemical pollutants, i.e. combustion residues and solvents. The EU Basic Safety Standards, stated in the Council Directive 2013/59/Euratom, based on the last recommendations from the International Commission on Radiological Protection (ICRP) and from WHO, are focusing on risks related to radon gas concentration inside dwellings and working places. On considering that Council Directive 2013/59 Euratom has to be transposed into law by each EU Member State by February 2018, it is recommended that radon issues have to be considered during the design phase of the building construction. For NZEB applications a special attention is requested when energy consumption is reduced lower and lower by taking care of airtightness. In such a case, indoor pollutants (chemical, radioactive, particulate, etc.) can significantly accumulate beyond safe levels. This paper describes measurements and remedial actions of study cases, focusing on public and domestic environments.

Segmented Gamma Scanning of Conditioned Radioactive Wastes: Development, Experimental Validation, and Application of an Angular Scanning Procedure for Hot-Spot Characterization

Abstract The “angular scanning” method allows both localization of hot spot(s) and the evaluation of the corresponding activity. Taking into account the experimental setup parameters (e.g., drum geometry, drum-detector distance, collimator geometry, etc.), the peak count rate versus the angular displacement is modeled as a theoretical analytical function of three independent variables (unknowns) for each hot spot: the two coordinates of the hot-spot center of mass and the corresponding activity value. Solutions for unknowns are obtained from equating, for each angular displacement, the experimental count rate to the corresponding theoretical one. Such a procedure has been applied to the SRWGA gamma scanner of the Casaccia Research Center utilizing a set of Waste Packages Reference Standards (with different matrices) where the gamma sources in different radial-azimuthal positions can be located.

L/ILW Waste Characterisation by the ENEA Multi-Technique Gamma System SRWGA

The S EA R adioactive W aste G amma A nalyser (SRWGA), is the gamma assay system of the ENEA Laboratory for L/ILW Waste Characterisation, which started operating in 1996 as a simple gamma scanner and has been under a continuous improvement process to became a multi-techniques system. The SRWGA is designed for the assay of radioactive waste drums containing gamma emitting nuclides. The system operates with an XtRa (extended range) Ge coaxial detector. This is liquid nitrogen colled, and shielded by means of a lead cylinder with two collimation windows; one mixed transmission source is provided. The system allows the application of four different measuring techniques, each one with its peculiar field of application, depending on waste characteristics or measuring time: Open Geometry, Segmented Gamma Scanning (with multi-energy transmission correction), Angular Scanning and, recently, Low Resolution Emission and Transmission Tomography, as the SRWGA is now endowed with new mechanical motions systems for tomographic capabilities. Tomographic reconstructions are obtained by means of a backprojection filtered by convolution methods (for transmission tomography) and Best Likelihood Maximisation (for emission tomography). The information obtained with transmission and emission tomography allows the localisation of matrix dishomogeneities and hot spots, carrying out a strong reduction of total activity uncertainties. This work presents the experimental results obtained using certified γ sources located in known matrices.Copyright

Self-Excited Plutonium X-Ray Emission in Plutonium-Bearing Materials

The presence of Pu X-ray peaks in the gamma spectrum of Pu-bearing materials [for example, PuO 2 and mixed-oxide (MOX) samples] is commonly attributed to alpha and gamma excitation. The aim of this work is the development of a mathematical model, based on the thick target yield approach, for both alpha- and gamma-induced fluorescence processes, thus enabling the quantification of the relative importance of these effects and the interpretation of the experimental data. Experimental data obtained at the Performance Laboratory (European Commission, Joint Research Center, Ispra, Italy) from well-characterized PuO 2 and MOX samples under well-defined experimental conditions are compared with the expected values based on the model developed, taking into account special self-attenuation of X rays from induced effects. Finally, a feasible application of the model is considered concerning the field of nuclear material accountancy and control; the possibility of inferring U and Pu concentrations in MOX from the normalized Pu K-shell X-ray counting rate is considered, and the expected performances are given.