The PASSAM project has been mounted in the frame of the 7th framework programme of the European Commission. Coordinated by IRSN, it involves eight partners from six countries, coming from different organization types: Technical Safety Organizations (IRSN), research (CIEMAT, CSIC, PSI, RSE, VTT) and utilities/industry (EDF, AREVA). They all have a strong experience and knowledge on severe accidents and more specifically of Filtered Containment Venting Systems and propose to share the work in a really complementary manner on this four years project (2013 – 2016). In case of a severe accident in a Nuclear Power Plant (NPP) fission products are released from the degraded fuel and may reach the environment if their confinement is lost and/or bypassed. Given the high radio-toxic nature of fission products for environment and population, it is absolutely necessary to avoid – or drastically reduce – their release. This highlights the importance of relying on effective mitigation systems capable of reducing as much as possible any accidental release. This overall statement becomes even stronger after the accident of March 2011 at the Fukushima Daiichi NPP. Current NPPs are furnished with safeguards based on the Design Basis Accident and some extensions to cope with accidents beyond the design bases. So, there are a number of mitigation systems within a NPP, both to accommodate the energy release and to deplete most of potential radioactive emission to the environment. Sprays, suppression pools, high efficiency particle filters, etc. are among those contributing to source term attenuation. The PASSAM project is of R&D experimental nature, aiming at:-exploring potential enhancement of existing source term mitigation devices,-demonstrating the ability of innovative systems to achieve larger source term attenuation.