1,721,084 research outputs found
Early effects comparison of X rays delivered at high-dose-rate pulses by a plasma focus device and at low dose rate on human tumour cells
No full textA comparative study has been performed on the effects of high-dose-rate (DR) X-ray beams produced by a plasma focus device (PFMA-3), to exploit its potential medical applications (e.g. radiotherapy), and low-DR X-ray beams produced by a conventional source (XRT). Experiments have been performed at 0.5 and 2 Gy doses on a human glioblastoma cell line (T98G). Cell proliferation rate and potassium outward currents (IK) have been investigated by time lapse imaging and patch clamp recordings. The results showed that PFMA-3 irradiation has a greater capability to reduce the proliferation rate activity with respect to XRT, while it does not affect IK of T98G cells at any of the dose levels tested. XRT irradiation significantly reduces the mean IK amplitude of T98G cells only at 0.5 Gy. This work confirms that the DR, and therefore the source of radiation, is crucial for the planning and optimisation of radiotherapy applications. © The Author 2015
Impact of a security event at a TRIGA reactor
No full textThe aim of this work is the study of the impact of security-related events and their consequences for research reactors, with particular emphasis on the off-site effects. The study case is done for the ENEA-Casaccia TRIGA RC-1 research reactor near Rome. The RC-1 Safety Report includes three different safety-related accident scenarios, namely the insertion of a step of positive reactivity, the uncontrolled extraction of all control rods at start-up or during a power variation and the emptying of the reactor pool. None of these scenarios imply radioactive releases at all. In this work, the focus is instead the description of the worst case scenario related to a security event and its consequences. Several possible scenarios have been analysed, however, the physical protection measures deter intrusions and, as shown by the Safety Report, even sabotage actions with major effects such as, the emptying of the reactor pool have no consequences on the fuel integrity. For these reasons, the worst security-related scenario considered in this work is a large plane crash with the complete destruction of the reactor hall and the reactor core. Propagation of the source term to the environment and the effective dose calculations have been performed using RASCAL, HOTSPOT and GENII codes following the ICRP-60 standards. © 2014 Elsevier Ltd. All rights reserved
Problemi di fisica del reattore ad acqua leggera e metodi di calcolo neutronico avanzati
Full text linkIl presente rapporto espone le principali problematiche di fisica dei reattori ad acqua leggera in relazione al loro calcolo neutronico, con particolare riguardo all'utilizzo di tecniche, metodi e codici avanzati di tipo deterministico. Vengono esposti e sintetizzati i principali progressi compiuti negli ultimi 15 anni circa, in relazione anche alle strutture a gruppi energetici ed ai metodi di calcolo più idonei al trattamento accurato delle sezioni d'urto efficaci e dell'autoschermo. Viene posta in evidenza l'importanza dell'aggiornamento delle sezioni d'urto associato al variare del burnup del combustibile ed alle variazioni spettrali connesse al buildup del plutonio o più in generale di isotopi fortemente assorbenti. Sono poi analizzate le problematiche derivanti dalla necessità di utilizzare combustibile ad alti burnup con il conseguente ricorso a veleni bruciabili per il contenimento della reattività a BOL ed i problemi di modellizzazione ad essi associati. Analogamente è fatto cenno all'impatto sulle tecniche di calcolo dell'utilizzo di combustibile MOX ed alle differenze rispetto a combustibile UOX. Sono poi esaminate le problematiche connesse al calcolo di interfaccia tra nocciolo e riflettore. Infine sono presentate le tecniche delle Probabilità di Collisione e del Metodo delle Caratteristiche per la risoluzione dell'equazione del trasporto dei neutroni per geometrie eterogenee complesse. Il presente Rapporto costituisce pertanto una base per le discussioni tecniche e per gli approfondimenti scientifici che si terranno nell'ambito dell'accordo STC recentemente firmato da ENEA e CEA sull'utilizzo dei codici deterministici Apollo2 e Cronos2 per il calcolo degli LWR. In particolare contribuisce allo sviluppo ed alla qualificazione di metodi e modelli di analisi e simulazione dei più recenti ed avanzati reattori ad acqua leggera di Generazione III e III+
Analysis and characterization of the X-ray beam produced by a PF device for radiotherapy applications
No full textA plasma focus device, devoted to the study of a possible application to the radiotherapy treatment of malignant cells, has been recently put into operation. The low-energy (up to 200keV) X-rays are produced by conversion of the electron beam generated by the device during the pinch phase. The X-ray spectrum has already been fully characterized, and an initial campaign of irradiation of specific cell cultures has been completed. At present, the links between the operational parameters of the actual device, the beam intensity, and the cell irradiation effects are being analyzed, trying to evaluate the advantage of the very high dose rate that can be delivered, of the order of several Gy in a few tens of nanoseconds. Preliminary results on radiobiological effectiveness are presented and discussed. © 2015 John Wiley & Sons, Ltd
The development of medicines for children. Part of a series on Pediatric Pharmacology, guest edited by Gianvincenzo Zuccotti, Emilio Clementi, and Massimo Molteni.
No full textThe lack of availability of appropriate medicines for children is an extensive and well known problem. As a consequence off label or unlicensed administration of medicinal products in every day paediatric practice is frequent. A variety of obstacles hinder the development of paediatric indications for drugs primarily intended for the adult market. The barriers to proper research on children's drug development include several complex factors, such as the limited commercial interest, lack of suitable infrastructure and competence for conducting paediatric clinical trials, difficulties in trial design, ethical worries and many others. Medicinal products used to treat children should be subjected to ethical research of high quality and be explicitly authorised for use in children as it happens in adults. Conducting adequate clinical trials in children is challenging and demanding. Identification of paediatric medical needs, extrapolation from adult data, modelling and simulation, specific clinical trial methodology are important features in the development of drugs intended for children. Market forces alone have proven insufficient to stimulate adequate research aimed at specific authorisation of medicinal products for the paediatric population, and for that reason, following the US experience, the European Paediatric Regulation has been amended in January 2007 by the European Commission. The objective of the Paediatric Regulation is to improve the development of high quality and ethically researched medicines for children aged 0 to 17 years, to facilitate the availability of information on the use of medicines for children, without subjecting children to unnecessary trials, or delaying the authorisation of medicines for use in adults. The impact of the Paediatric Regulation reflects in an increase in the number of paediatric studies to be performed, even if a significant number of these studies have not started yet. The objective of this review is to describe the main regulatory and scientific features which play a role in the complex issue of paediatric drug development
Kinetic Description of Rotating Gases in External Magnetic Fields in the Framework of the Thomas-Fermi-Dirac Approach
No full textAim of this work is to extend the results obtained in a previous study on the magnetic confinement and stability of a rotating quantum degenerate fermion gas. This extension consists in the inclusion in the previously set up model of the effects of the exchange forces, and generalises the Thomas-Fermi (TF) approach used in the referenced work towards a Thomas-Fermi-Dirac (TFD) statistical description. The TF model has not only been used extensively and with success in these years to study atomic, nuclear, and molecular properties, or to evaluate features of matter in extreme conditions such as low temperatures and/or high densities typical of astrophysics and inertial confinement fusion experiments, but also to found hydrodynamic theories for the diffusion and stability of fermion plasmas (Rozsnyai, B. F. (1972). Relativistic Hartree-Fock-Slater calculations for arbitrary temperature and matter density. Phys. Rev. A 5(3):1137-1149), one component nonneutral degenerate fluids, plasmas etc. In this article an equation for density profiles in cylindrical symmetry is found, from the semiclassical kinetic theory of quantum uses (Pathria, R. K. (1996). Statistical Mechanics. 2nd ed. Oxford: Butterworth & Heinemann). which takes into account the effects of temperature, average velocity, external magnetic field and quantum exchange. Numerical and approximate analytical solutions of this equation for the case of complete quantum degeneracy are given and comparisons with the previous results are carried out
Current and heat flux in a degenerate plasma
No full textLooking at the model for a degenerate electron gas in metals at very low temperature, we studied the macroscopic balance equations for current density and heat flux and we analyzed the effects produced on some transport coefficients if the quantum aspects are taken into account. The corrections for diffusion coefficients, electrical conductivity, etc., are explicitly carried out for a quite general collision model and the relations between these transport coefficients are pointed out
D07 - Definition of the ETDR core and neutronic characterization - PART I
No full textThis report concerns the preliminary design and the neutronic characterization of the ALFRED core (Advanced Lead-cooled Fast Reactor European Demonstrator), a criticaI reactor (300 MWth) for the demonstration ofthe Lead-cooled Fast Reactor technology chain in the framework ofthe LEADER project (VII EURATOM FP).
Here the materials specifications, the core design and configuration, the power deposition distribution, the controllsafety systems, the feedback reactivity effects, the irradiated fuel composition and the burnup swing are reported. The used codes are MCNPX and ERANOS.
This work has been performed by ENEA and CEA, in collaboration with SCK-CEN
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