Unsteady aspects of sodium-water reaction water cleaning of sodium containing equipments

Fast Sodium Reactor (FSR) is one of the most promising nuclear reactor concept ('Generation IV systems') to be issued in the next decades (P. Martin, 2007). This technology is intended to be much safer, to have a significantly better yield and to produce less wastes with a lower nocivity. Liquid sodium is used as the thermal fluid in direct contact with the nuclear core. Ideally, the heat extracted should be transferred between sodium and water in steam generators. Anyway when sodium is brought in contact with liquid water, a highly exothermal chemical reaction ensues which is believed to be explosive in certain situations (J.A. Ford, 1965). Such a contact may happen in a number of instances (repairs, decommissioning,..) and not only during major accidents. Unfortunately the reasons for which the mixing of sodium with water may lead to an explosion, generating blast waves like an explosive material, do not seem to have been clarified so far not even deeply studied. The primary objective of this PhD work is thus to identify the details of the phenomenology, to isolate the leading mechanisms and to propose a modelling approach. (author)