Severe Accident Phenomenology Analyses and Fission Gas Release in Advanced Nuclear Reactors

The aim of this work is to contribute to qualify a model in order to simulate the progression of a severe accident (SA), evaluating the Source Term during SA scenarios for a III Generation nuclear power plant (NPP), as AP1000 and EPR. The present Ph.D. thesis is articulated in 3 different parts. The first part is a status of the art on the SA phenomenology and on the Lumped Parameter Codes involved in the analyses. The aim of second part of the work is to give an overview on the phenomena and on the ability of code models to follow the progression of the test scenarios. The third part of the thesis concerns SA sequence analyses of AP1000 plant.