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Sodium Pool Heating and Fire – Experiments and Modeling

pubblicazioni - Poster

Sodium Pool Heating and Fire – Experiments and Modeling

The Sodium-cooled Fast Reactor (SFR) system is a Gen IV fast-neutrons spectrum nuclear reactor, using liquid sodium as coolant. Sodium is an effective coolant because of its good properties (efficient heat transfer, low melting temperature, high vaporization temperature, low viscosity, no solid crust – layer formation), but it is causing a considerable risk if a leak occurs in the cooling system, as sodium is a very reactive metal with oxygen and water. A sodium fire can have a significant effect, even if the HRR produced by combustion is usually lower than that of conventional hydrocarbon fires, because of the damage risks for electrical – mechanical equipments and concrete. Furthermore, sodium burning is generating very opaque and dense sodium oxides – hydroxide aerosols that are damaging visibility, breathing and materials. Another important phenomenon is the reaction of sodium with water (liquid or steam) that is a fast exothermic reaction generating sodium hydroxide and hydrogen which can burn very quickly.The poster briefly describes a mathematical model focused on simulation of dynamic development of liquid sodium pool heating and fire. The model is finalized to calculate the pool temperature field for the heating phase and also the vapor mass release rate from the pool to the surrounding air in case of fire. In particular, the lumped parameters grid – network theory is used to model the pool heat transfer and vapor generation phenomena (equivalent circuit model).The “grid” model was developed to extend the capability of numerical tools CORIUM-2D and ECART and its development was focused on the following implementation inside such codes (CORIUM-2D is a lumped parameters code dedicated to analyze the thermal behavior of a light water or sodium nuclear reactor in case of normal operation or severe accident scenarios; ECART is a lumped parameters numerical tool focused on consequences prediction of an accident in nuclear – conventional installations with airborne transport of dangerous substances and fires). The model, after a first validation of a stand-alone version, was implemented inside ECART, while the development of CORIUM-2D version that uses this model is currently under development. The model and improved codes validations are carried out by comparison with reference data and results of experimental tests performed at RSE. At present, the model approach appears as an effective fast-running tool to simulate the sodium pool heating and fire dynamics.

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