1,721,249 research outputs found
L’energia nucleare da fissione come fonte energetica durevole ed alternativa ai combustibili fossili
No full textNuclear fission energy as a long term alternative to fossil fuels
No full textThis paper investigates the role that nuclear fission energy could play in assuring a reliable energy supply, in a sustainable development scenario with the aim to limit the global warming rise to +2 °C. Reference to scenario "IPCC IS92a, Business as Usual" will be used and kept out with the history of the world primary energy consumption from 1970 to 2005. Besides, in the medium-long term, growing fission nuclear energy rates are hypothized from 29.3 EJ (ExaJoule) in 2005 to about 400- 500 EJ by the end of the century. This would entail generating about 80% electricity by nuclear power sources. This aim is within reach of today's day nuclear technology and has already been attained in France. Technological innovation and the free markets are pushing us towards a global economy; in this context nuclear power could enlarge its range and be used for large powered ships, see water desalination, cogeneration, hydrogen production, electric rail roads and domestic use. On the basis of the scientific and technological know how one can evaluate energy supplies that, by the end of the century, could lead to the transition from thermal nuclear fission reactors to fast nuclear fission reactors. Such reactors allow a more efficient use of nuclear fuel of about 160 times more than thermal reactors, and the extractable energy from raw materials is 160 times higher. Parametric studies have allowed to evaluate uranium use both for thermal and fast reactors on the basis of the present inventory of uranium resources. Even if we were to imagine costs 10 times higher than today's price of the spot market, results show that the impact of nuclear fuel has been evaluated for final cost of electricity generation that is not 3-4% higher than total cost
Vapour Condensation in Presence of Air in the TOSQAN Facility: A Computational Analysis
No full textThe present work is focused on the transient computational analysis of a test performed in the French facility TOSQAN. The aim of the study is to contribute to the understanding of the heat and mass transfer mechanisms involved in the problem and to check the possibility of employing a multipurpose commercial CFD code to predict a containment transient and the mass transfer phenomena of interest in the nuclear field. In particular, the effect of the condensation rate at walls through the liquid-gas interface was simulated by appropriate source terms, introduced directly into the mass, species and energy balance equations, evaluated on the basis of the vapour concentration gradient near the vessel walls. To make feasible the numerical solution of the problem by the FLUENT code, the assumption of an extremely thin water film was utilized. In the present paper the calculated time-dependent average temperature and pressure of the atmosphere inside the TOSQAN vessel are compared, together with the steady state temperature profiles, with the available experimental data
SIMMER code two-fluid model well-posedness and stability for simulating liquid metal (lead–lithium eutectic), water vapor, and non-condensable gases multi-component multi-phase flows
No full textLiquid metals are employed as a coolant in liquid metal fast reactors (LMFR) and are considered breeders and coolants for future power-producing fusion reactors. The interaction of liquid metals with other coolants, such as air and water, is one of the possible occurrences in liquid metal-cooled reactors. Although the SIMMER-III computer code is currently in the validation and verification phase, it is a prospective candidate code for correctly investigating possible accidents. This study aims to determine the stability and well-posedness of the SIMMER-III code Eulerian-Eulerian two-fluid model (TFM) under any such accident scenario. This work also considers the influence of the virtual mass force and diffusion forces in momentum on TFM stability in accelerated liquid metal, steam, and non-condensable gaseous flows throughout all flow regimes. The characteristics method is used to assess the ill-posed nature of TFM for all types of accidents and accident scenarios in a hypothetical simplified system model with several components (Lead-Lithium, non-condensable gases, and water vapor). It has been discovered that the analysis findings vary from the air and water two-component two-phase flows (characteristics roots spectrum and error growth rate patterns) and are particularly sensitive to the diffusion and virtual mass coefficients. This is because liquid metals have a higher density than liquid water and steam, resulting in strong virtual mass forces and weak diffusion forces in liquid-metal and gas two-phase flows. Because of the extensive range of possible interactions between fluxes of different components, producing an accurate representation of diffusion in multi-component mixtures is difficult. Because of this, it is strongly suggested that the virtual mass coefficient and diffusion coefficients be handled more accurately for these kinds of flows. The values of these coefficients significantly affect how accurate proposed TFM predictions are, but there hasn't been much research on how to estimate them. The study also sheds light on the model's accuracy and highlights the areas where the model's predictions will be mathematically trustworthy
Investigating HLM-Water Interaction Experiments in LIFUS5/Mod2 Facility
No full textThe interaction between heavy liquid metal (HLM) and water is a safety concern for the preliminary designs of lead fast reactor and of subcritical transmutation system prototypes. Current pool-type configurations have the steam generators inside the reactor vessel. This implies that the primary to secondary leak (e.g. steam generator tube rupture) shall be considered as a safety issue in the design, and in the preliminary safety analysis, of this reactor types. This requires availability of qualified experiments carried out with initial and boundary conditions representative of the reactor prototype. The objective is to support the development and to demonstrate the reliability of computer codes in simulating the phenomena of interest. LIFUS5/Mod2 is a separate effect test
facility, designed for investigating the interaction between heavy liquid metal (HLM) and water, installed at ENEA CR Brasimone. LIFUS5 test facility is refurbished based
on the operating experience acquired during the previous experimental campaigns and the support of numerical tools (i.e. SIMMER-III, -IV and, with some extent, RELAP5).
The new design involves a new facility configuration, test section, instrumentation and control systems. This paper presents the LIFUS5/Mod2 facility, the instrumentation, the
final test matrix and the experimental campaign performed in the framework of the EC funded THINS Project and thanks the support of the Italian Ministry for the Economic Development
Haptic Wearable System to Assist Visually-Impaired People in Obstacle Detection
Full text linkOne of the main difficulties encountered every day by visually-impaired people concerns moving and orienting themselves independently and safely in indoor and especially outdoor environments. Although several studies have been carried out to propose electronic aids to support orientation and mobility tasks, problems continue to exist. In this work, a wearable ultrasonic-based obstacle detector is proposed to give a further contribution to the field. The prototype is designed by paying particular attention to (1) the updating of the components and (2) the use by the blind users. It can be mounted on the user’s preferred model of eyeglasses and can be used with or without the traditional white cane
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