Fission-product aerosols in the reactor containment under severe accident conditions

In the framework of probabilistic risk assessments severe reactor accidents are analyzed with respect to their radiological impacts on the environment. In this connection, radioactive fission and activation products as aerosol particles generated upon core melting and subsequently released into the containment play an essential role. During the past decade fission product release and aerosol formation have been extensively investigated and modelled within the SASCHA program. The NAUA computer model simulates the long-term behavior of aerosol particles in the accident atmosphere of a containment taking into account various physical plate-out mechnisms. NAUA was verified on the data basis developed from the DEMONA series of experiments. Both models were applied to the description of the fission product and aerosol behavior during a postulated severe core accident in a modern pressurized water reactor. (orig.)