Impact of aerosols emitted during a fire on the containment of nuclear facilities

This research, carried out within IRSN's Laboratory of Physics and Metrology of Aerosols (LPMA) in Saclay, are motivated by the need to develop models that can predict the levels and consequences of particulate emissions encountered in fire accident situations. A synthetic scheme presents all research topics related to the impact of these particulate emissions, i.e. the suspension of radioactive particles during fire, the production of carbon aerosols by combustion processes and the physico-chemical behavior of aerosols emitted during a fire. The first theme aims to predict the amount of radioactive material particulates that can be suspended in the event of a fire and at the same time be transported to the fire room or to the ventilation network. This first part focuses more specifically on the work done on the suspension of radioactive particles during a glove box fire involving polymeric materials. The second theme aims to predict the properties of the particles emitted specifically by the thermal degradation of the materials involved during a fire. The knowledge of the physicochemical characteristics of these aerosols is essential if one wants to understand their behavior within a nuclear base facility (NBF). The metrological developments carried out are detailed and applied to characterize the particulate emissions and predict their physico-chemical properties. The third thematic aims mainly to develop a predictive model of pressure drop in high efficiency filters used as containment barrier within NBF ventilation networks. To do this, estimating the amount of particles that can be trapped by the filter requires understanding of the mechanisms of transport and evolution of aerosols within the local fire headquarters and the ventilation network. The agglomeration and thermophoresis deposit of these particles is studied. In a second step all the experimental and theoretical developments carried out in order to predict the clogging of the filters with very high efficiency by representative fire soot are detailed. Recent developments on the mechanisms of oxidation and sorption of water on soot and the metrological developments undertaken to characterize their surface chemistry are presented. (author)