1,721,096 research outputs found
A Personal Neutron Monitoring System Based on CR-39 Recoil Proton Track Detectors: Assessment of Hp(10) Using Image Process Algorithms
No full textAt the Individuai Monitoring Service (IMS) of the ENEA Institute far Radiation Protection (IRP), the Hp(10) fast neutron dosemeter consists of a CR-39 (PADC, poly allyl diglycol carbonate) recoil protons track detector. The tracks across the detector surface are magnified through a chemical etching procedure and counted by a semi-automated system which consists of a microscope, a camera and a Pc. A new analysis system, based on the NationailInstruments vision tools, was developed. The track area distribution far each reading field is recorded and numerical algorithms were developed in order to correct the energy dependence of the response and to recognize the tracks due to the background. This improves the dose evaluation system in terms of accuracy and discrimination of the background
Development of automatic systems for the ionising radiation metrology at the ENEA-IRP secondary standard laboratory
No full textThe ENEA IRP Secondary Standard Dosimetry Laboratory of Bologna (Italy) has been operated for more than 30 y as a secondary standard laboratory for X rays, gamma, beta and neutron radiation metrology. For photon radiation, the instruments for radiation protection and clinical dosimetry are calibrated in agreement with the ISO standards, using remotely controlled irradiation units: two 60Co, one 137Cs and three X-ray units (160, 320 and 420 kV, respectively). The calibration procedures, approved by the National Primary Laboratory, have been recently implemented in a software package, which controls the irradiation units and acquires the reference measurements. The system, developed at the laboratory under the LabVIEW programming language, guarantees a constant surveillance of all devices and operations, avoids procedural mistakes and automates the record-keeping and reporting activities. This results in an increase in the reliability of the calibration service
Developing a thermal neutron irradiation system for the calibration of personal dosemeters in terms of Hp(10)
No full textAt the ENEA Radiation Protection Institute in Bologna a thermal neutron irradiation facility is available for the calibration of neutron dosemeters. It consists of a 1 m x 1 m x 1 in polyethylene cube containing three 241 Am-Be sources of about 185 GBq. The cube contains three co-axial cylindrical calibration cavities of different dimension. Due to their limited dimensions, the cavities do not allow the calibration of thermal neutron personal dosemeters in terms of Personal Dose Equivalent Hp(d), that should be carried out on the.30 cm x 30 cm x 15 cm ISO phantom. The study herewith presented was addressed at adapting the facility for external irradiation of personal dosemeters on the ISO phantom. Extensive Monte Carlo studies were carried out to characterise the neutron fluence spatial distribution along the front face of the phantom. A satisfying neutron field homogeneity within the measurement area has been obtained by means of a pyramidal polyethylene fluence flattening filter and the selection of the proper cube to phantom distance. This new irradiation set-up was experimentally tested through measurements with activation foils, according to the spatial mapping array taken from the calculations
Field parameters and dosimetric characteristics of a fast neutron calibration facility: Experimental and Monte Carlo evaluations
No full textAt the ENEA Institute for Radiation Protection (IRP) the fast neutron calibration facility consists of a remote control device which allows locating different sources (Am-Be, Pu-Li, bare and D2O moderated 252Cf) at the reference position, at the desired height from the floor, inside a 10 x 10 x 3 m3 irradiation room. Either the ISO reference sources or the Pu-Li source have been characterised in terms of uncollided H*(10) and neutron fluence according to the ISO calibration procedures. A spectral fluence mapping, carried out with the Monte Carlo Code MCNPô, allowed characterising the calibration point, in scattered field conditions, according to the most recent international recommendations. Moreover, the irradiation of personal dosemeters on the ISO water filled slab phantom was simulated to determine the field homogeneity of the calibration area and the variability of the neutron field (including the backscattered component) along the phantom surface. At the ENEA Institute for Radiation Protection the calibration of neutron area monitors as well as personal dosemeters can now be performed according to the international standards, at the same time guaranteeing suitable conditions for research and qualification purposes in the field of neutron dosimetry
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Spuntik 50 mezzo secolo di osservazioni spaziali
No full textUn CD rom realizzato in occasione dei 50 anni dal lancio del primo satellite artificiale (lo Sputnik) che ripercorre il perodo fra il 1957 (lancio dello Spuntik) al 1969 ("lo sbarco" dell'uomo sulla Luna), raccontando non solo cio' che attiene prettamente all'astronomia, ma anche al costume, alla politica e ai grandi mutamenti socio culturali che hanno caratterizzato il nostro paese in quegli anni
Inter-comparison among different TLD-based techniques in a standard multisphere assembly for the characterisation of neutron fields
No full textIn the framework of collaboration among the ENEA Radiation Protection Institute (Bologna), the ENEA Fusion Department (Frascati) and the INFN-LNF-Radiation Protection Group (Frascati), an experimental campaign was organised on the usage of thermoluminescence dosemeters (TLDs) for the dosimetric and spectrometric characterisation of neutron fields. Commercially available TLDs of different material and different sensitivity to photons and thermal neutrons were selected, namely TLD600H and TLD700H from Harshaw, GR206 and GR207 from SSDML (China), MCP-6s from TLD Poland. The detectors were first calibrated in standard fields of photons (60Co) and thermal neutrons at the ENEA-IRP Secondary Standard Calibration Laboratory of Bologna, then exposed in fast neutron standard fields of different energy, using a standard multisphere moderating assembly. The paper compares the dosimetric characteristics of the studied TL detectors, underlining the (n-γ) discrimination capability, and discusses their spectrometric performances addressed to radiation protection applications
The ENEA criticality accident dosimetry system: A contribution to the 2002 international intercomparison at the SILENE reactor
No full textThe present paper summarises the activity carried out at the ENEA Radiation Protection Institute for updating the methodologies employed for the evaluation of the neutron and photon dose to the exposed workers in case of a criticality accident, in the framework of the 'International Intercomparison of Criticality Accident Dosimetry Systems' (SileÃne reactor, IRSN-CEA-Valduc June 2002). The evaluation of the neutron spectra and the neutron dosimetric quantities relies on activation detectors and on unfolding algorithms. Thermoluminescenct detectors are employed for the gamma dose measurement. The work is aimed at accurately characterising the measurement system and, at the same time, testing the algorithms. Useful spectral information were included, based on Monte Carlo simulations, to take into account the potential accident scenarios of practical interest. All along this exercise intercomparison a particular attention was devoted to the 'traceability' of all the experimental and computational parameters and therefore, aimed at an easy treatment by the user
Implementazione di un sistema di lettura automatico per dosimetri per neutroni veloci di CR-39 nel servizio di dosimetria dell'Istituto di Radioprotezione dell'ENEA
No full textIl Servizio di Dosimetria dell'Istituto di Radioprotezione dell'ENEA fornisce, da circa vent'anni, dosimetri di CR-39 per la dosimetria dei neutroni veloci.L'esperienza sviluppata in questi anni nelle tecniche di sviluppo e lettura dei rivelatori, ha permesso successivi miglioramenti delle procedure utilizzate ai fini di una maggiore accuratezza ed efficienza.Il presente lavoro si propone di illustrare l' implementazione di un sistema di lettura automatico per dosimetri di CR-39 per neutroni veloci, recentemente sviluppato e realizzato all'Istituto di radioprotezione dell 'ENEA, nella routine del Servizio Dosimetrico. Il nuovo sistema, basato su di un software di Visione automatica della National Instruments, oltre a rendere più rapida e riproducibile la procedura di lettura, permette di migliorare la valutazione delle dosi in termini di accuratezza e di prestazioni nel campo delle basse dosi. Il sistema è dotato, sia di algoritmi di analisi geometrica delle tracce, sia di algoritmi per la correzione della dipendenza energetica della risposta e la discriminazione delle tracce di fondo.Al termine della realizzazione del sistema è stato avviata la sua introduzione nella routine del servizio di dosimetria. Ciò costituisce il delicato ed importante anello di congiunzione fra l'attività di ricerca e l'attività di routine di dosimetria, che comporta il passaggio dalla fase prototipale e/o sperimentale alla fase di routine, caratterizzata da tempi, numeri, tipo di misure ben diversi da quelli studiati durante gli studi e le ricerche. Ciò comporta l'effettuazione di una serie di procedure e verifiche, raramente descritte in letteratura e qui riportate, fondamentali per l'implementazione reale dei risultati degli studi e l'effettivo miglioramento della qualità del servizio fornito.Il presente lavoro illustra, inoltre il confronto delle prestazioni del nuovo sistema con quelle del sistema semi-automatico fino ad ora in uso, sulla base delle misure di routine di un periodo di controllo del servizio di dosimetria
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