ABSTRACT
Generation IV nuclear reactors are a set of systems whose designs are currently the object of several researches, with the main goals of improving four key-issues (sustainability, economics, safety and reliability, proliferation resistance and physical protection) of Nuclear Power Plants (NPPs).
The Sodium-cooled Fast Reactor system, in particular, is a Gen IV fast-neutrons spectrum reactor, using liquid sodium as coolant, that make possible efficient fuel cycle and management of actinides (plutonium, neptunium, americium, curium, californium).
Liquid sodium has good properties as a coolant, but its use implies a significant 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 though the HRR produced by combustion is usually much less compared to conventional hydrocarbon fires. Its burning is accompanied by the production of an opaque and dense sodium oxides smoke. In addition, metallic sodium has a fast exothermic reaction with liquid water or steam to form sodium hydroxide and hydrogen. The paper presents a literature review of the current state-of-knowledge related to liquid sodium behaviour in relevant safety cases and the experiences of some past incidents.
Keywords: Nuclear fast reactors, Generation IV, Sodium fire, Aerosol, Sodium oxides and peroxide.
