In a sodium cooled fast reactor (SFR), a severe transient condition (i.e. hypothetical core disruptive accident (CDA)) is the design extension condition resulting from the mismatch of power produced and power removed from the reactor, as well as from the shutdown system not responding on demand, typically under conditions of either unprotected loss of flow or unprotected transient overpower events. The assessment of the consequences of a CDA in terms of radioactivity release outside the containment system, which may affect the environment and the public, is of paramount importance from the point of view of public acceptance of nuclear power, especially after the Fukushima Daiichi accident. The objective of this CRP is to make realistic estimates, through numerical simulations, of the fission product transport mechanisms in typical pool type SFRs and to determine the fission products retained within the reactor primary vessel and ejected into the reactor containment building. The exercise would be carried out for a reference pool type SFR of 500 MW(e) capacity fuelled with mixed oxide fuel, i.e. the Prototype Fast Breeder Reactor in Kalpakkam (India).