Papers by Giovanni Manzini
Volume 4: Computational Fluid Dynamics (CFD) and Coupled Codes; Decontamination and Decommissioning, Radiation Protection, Shielding, and Waste Management; Workforce Development, Nuclear Education and Public Acceptance; Mitigation Strategies for Beyond Design Basis Events; Risk Management, 2016
Confined vented explosion is a very complex topic as many parameters affect the phenomena, mainly... more Confined vented explosion is a very complex topic as many parameters affect the phenomena, mainly because the flame front develops from an ignition source and travels through a medium which may involve complex boundary conditions and obstructions of various geometries. Therefore, in the plant safety assessing step, it is important to provide correct estimates of the flame spreading rates as well as overpressures which may result from various explosion initiation scenarios. This will help designers for plant layout optimisation with the aim to minimize the risk associated with those events. Although hydrogen explosion in unvented compartments was often simulated in the past, there were not many opportunities, so far, to simulate explosion in a vented room. With this purpose, a benchmark exercise was organized, based on simple hydrogen combustion experiments, performed in a vented compartment (Chamber for View of Explosion – CVE) at the Scalbatraio laboratory of University of Pisa (It...
Energy Procedia, 2015
The fire risk in the photovoltaic systems has emerged over the years as not negligible, setting i... more The fire risk in the photovoltaic systems has emerged over the years as not negligible, setting in motion a process, which involves various organizations (control Authorities, standardization bodies, modules manufacturers, etc.) for achieving the codification of construction, design and installation of these systems and their components to minimize fire risk. Currently, European standards focused specifically on fire behavior of PV modules don't exist yet, so test protocols focused on other equipment are used to test PV modules reaction to fire. About that, a research program was carried out to do a short analysis of PV systems fire events, to analyze the current test protocols and for identifying their criticalities and possible improvements. In particular, some variants of these protocols have been developed basing on some of the existing test protocols in standard harmonized at European level about reaction to fire of construction products. These variants have been designed for being specific test tools for determination of reaction to fire features of PV modules with main attention to important peculiarities such as: modules inclination, initial fire particularly aggressive.
On the basis of reasonable core meltdown conditions that can be postulated for GenIV sodium fast ... more On the basis of reasonable core meltdown conditions that can be postulated for GenIV sodium fast reactors, during a severe accident, good safety margins can be achieved for corium confinement and cooling inside the reactor vessel, by the use, in the lower plenum, of a core catcher. Such a device has to be designed to withstand to extreme thermal-mechanical conditions that rise as consequence of the large mechanical energy release and high temperature of molten corium. In the frame of the activities carried out within the CP-ESFR Project of the 7th Framework Programme Euratom, and considering the postulated accident conditions assumed for a reference 1500 MWe pool-type sodium fast reactor, the present work provides a preliminary analysis of the thermal response of a possible core catcher placed within the vessel. The dynamic thermal behaviour of the corium-structure-coolant system is analyzed with the computer code CORIUM-2D, an original simulation tool developed by RSE with the aim ...
The international nuclear power community has proposed six new Generation IV nuclear reactor desi... more The international nuclear power community has proposed six new Generation IV nuclear reactor designs for use later this century. These include reactors cooled by gas, lead and water, as well as high molten salt reactors and the SFR (Sodium-cooled Fast Reactor) [1] (Figure ). To support the development of these innovative reactors, a wideranging research and development programs are now under way. A number of technology goals lie on the research -for example, improving nuclear safety and reliability; sustainability and minimizing waste; and reducing the cost of building and running nuclear plants. The SFR, in particular, is a fast-neutron spectrum one with a closed fuel cycle for efficient conversion of fertile uranium and management of actinides. The SFR reactor uses a fast neutron spectrum and liquid sodium as coolant to remove the heat from the core. In effects, the liquid sodium is an excellent cooling agent, mainly because of his its good heat transfer capabilities, low melting point (97.8 °C at p= 1 atm) and large margins to the boiling point (883 °C, at p= 1 atm) at ambient pressure and also low viscosity. The SFR can increase the efficiency of uranium usage by breeding plutonium and it is designed to allow any transuranic isotope to be consumed (and in some cases used as fuel). In practice, due to the its fast neutron spectra, SFR has the capability to utilize almost all of Energia & Ricerca LA TERMOTECNICA luglio/agosto 2012
The assessment and implementation of adequate systems and procedures (leak before break, defense ... more The assessment and implementation of adequate systems and procedures (leak before break, defense in depth, ...) is essential to minimize the probability and consequences of sodium leaks (risk of sodium combustion, sodium -water, sodium -water -air and sodium concrete reactions) in the Gen IV SFRs. To achieve this goal, past experience is very essential. However, also experimental and numerical simulations activities are very important to improve safety systems design and accident management procedures. Through LISOF experiments useful indications about the influence of oxygen concentration on sodium combustion ignition (spray and pool fires very frequently if [O 2 ] > 14%) were obtained. Another evident feature of liquid sodium at high temperature (550 °C) is its remarkable ability to penetrate through small cracks and seals. A pool fire model was implemented in ECART code and a spray fire model implementation is currently in progress.
The Sodium-cooled Fast Reactor (SFR) system is a Gen IV fast-neutrons spectrum nuclear reactor, u... more The Sodium-cooled Fast Reactor (SFR) system is a Gen IV fast-neutrons spectrum nuclear reactor, using liquid sodium as coolant fluid. This makes possible more efficient fuel cycle and management of actinides (plutonium, neptunium, americium, curium, californium).
In order to verify the effectiveness of different fire protection strategies applied to subway an... more In order to verify the effectiveness of different fire protection strategies applied to subway and road tunnels, numerical analyses were performed using a multi-scale approach with different tools, as CFD simulations appear, in many cases, too long-running for a direct application. The regions of the domain where the main phenomena are foreseen in huge civil transport scenarios are small compared to overall compartment, requiring the accurate analysis just of a small portion which need correct initial and boundary conditions. This goal can be achieved by means of a "cascade" of simulations performed in spatial and temporal domains which are progressively smaller, to obtain, gradually, an improved accuracy of results in the area and time interval of main interest. To do that, the analysis was divided into three main steps and we used a correlations toolbox (1° step) and then a set of one-dimensional (2° step) and three-dimensional (3° step) numerical tools.
INTRODUCTION The research is focused on the development, verification and validation of a mathema... more INTRODUCTION The research is focused on the development, verification and validation of a mathematical model The research is focused on the development, verification and validation of a mathematical model simulating some phenomena of the dynamical development of a pool fire. The lumped parameters grid theory is used to model the pool heat transfer and vapor generation phenomena. This model is finalized to quantify the vapor mass release rate, from the pool to the surrounding air, This model is finalized to quantify the vapor mass release rate, from the pool to the surrounding air, caused by pool liquid heating consequent of radiative and convective heat transfer phenomena between flame (and eventually other high temperature bodies) and pool. The " grid " model has been between flame (and eventually other high temperature bodies) and pool. The " grid " model has been developed to extend the capability of ECART numerical tool and his development was focused on the ...
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Papers by Giovanni Manzini