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pubblicazioni - Memoria

Characterization of the liquid sodium spray generated by a pipework hole

pubblicazioni - Memoria

Characterization of the liquid sodium spray generated by a pipework hole

La memoria presenta una descrizione sintetica dell’attrezzatura di prova LISOF (LIquid SOdium Facility) e, a seguire, riporta i risultati delle esperienze eseguite con sodio liquido ad alta temperatura (550 °C). Le esperienze hanno riguardato la caratterizzazione di sprays e l’innesco d’incendio di sodio liquido ad alta temperatura e lo studio del comportamento all’incendio di un simulacro di core catcher investito da sodio liquido ad alta temperatura.

Fast reactors well represent one of the technologies considered in the so called Generation IV nuclear reactors. Among the fast reactor systems, the Sodium-cooled Fast Reactor (SFR) has the most comprehensive technological bases, thanks to the experience internationally gained from operating experimental prototypes and commercial-size reactors. On the other hand, while sodium has very good thermodynamic properties as regards the nuclear reactor, it chemically reacts in the case of contact with water or air and, then, presents a significant risk of fire if a leak occurs in the cooling system. In this context, an experimental study was dedicated to support the development and validation of aerosol simulation models to be used for plant safety analyses. The tests were performed with the lab-scale apparatus LISOF (LIquid SOdium Facility), specifically designed for the characterization of liquid sodium droplets ejected from prepared micro-holes representative of possible structural defects. Sodium is heated up to 550° C in a steel container installed in the LISOF facility. The liquid sodium spray is generated by opening a release valve and pressing the liquid sodium to flow through ad-hoc orifices. LISOF has two opposite thick glass windows (850 mm x 850 mm), through which high-speed videos are recorded, and two thick circular sapphire windows through which spray characterization is made using laser beams (PDA method). Because of safety reasons, the whole apparatus is installed within a proper large chamber and managed by a remote control system. The paper reports the experimental results obtained with sodium sprays generated through orifice diameters of 0.2 mm, 0.4 mm and 0.5 mm, both in air at room conditions and in inert atmosphere. The characterization of the obtained sprays is given in terms of droplets dimensions, velocity, quantitative distribution vs dimensions and behaviour of the ignition process in the presence of oxygen. Preliminary qualitative results of the interaction of the liquid sodium jet with a concrete sample are also reported.

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