Improved modelling of sodium-spray fires and sodium-combustion aerosol chemical evolution

​International Congress on Advances in Nuclear Power Plants (ICAPP 2015) / 3-6 mai 2015, France

​In the context of the Generation IV initiative (www.gen-4.org) and, more immediately, the strategic choice France may make in the coming years regarding development of nuclear power, sodium-leak accidents in sodium-cooled fast-neutron reactor (SFR) facilities are the subject of renewed interest. Pyrophoric, the sodium will burn upon contact with air in a containment creating toxic aerosols. Primary sodium will also be activated and contaminated so fire aerosols are not only toxic but also act as the main vector for radionuclide transport to the environment in the event of a confinement problem. In the past, the principal goal of safety studies concerned dimensioning the containment in terms of temperature and pressure rise due to fires. However, to assess a source term, we must take account of the fire aerosols in relation to radiocontaminant transport. First, we must evaluate the quantity of aerosols produced during a sodium fire. This is the goal of the work presented here: we develop the numerical simulation NATRAC to calculate the mass of aerosols produced during a spray fire such as may be considered for a SFR severe accident. The results show that the mass of oxide aerosols produced by a sodium spray fire can involve more than 60% of the ejected sodium.