IRSN, Institut de radioprotection et de sûreté nucléaire

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Enhancing Nuclear Safety


Research programs

CESAM project

​Last update on March 2013

CESAM (Code for European Severe Accident Management) is a project that aims to consolidate ASTEC, a software system for modelling nuclear reactor core meltdown accidents, as a European software of reference for the study of severe accidents, and in particular their management, in all types of Generation II and III reactors. Launched as part of the 7th Research and Development Framework Program (RDFP) of the European Commission, the project will begin in April 2013 and last four years.


Context and objectives


The accident at Fukushima in March 2011 highlighted the need for digital modelling tools for nuclear reactor core meltdown accidents, using state-of-the-art knowledge and validated as far as possible with test data. Their use in crisis situations depends mainly on improved performance and their integration with tools for modelling the spread of radioactivity in the environment. The CESAM project aims to meet these objectives by further developing the core meltdown accident modelling software ASTEC.





In a first phase, ASTEC's existing models representing the phenomena that occur during a core meltdown accident will be analysed based on our knowledge of the phenomena dominant in the Fukushima accident.  On this basis, IRSN and GRS will improve ASTEC's existing models or create new ones. In addition, ASTEC will be extended towards diagnostic applications in crisis situations, on the one hand by coupling this software with tools for assessing the atmospheric dispersion of radioactivity release outside the containment building, and on the other hand by developing a method – based on Bayesian networks – for tracing back to possible radioactivity release scenarios using measurements performed during an accident. Efforts will also be made to reduce the computation time. Finally, reference ASTEC data sets for every type of nuclear reactor in Europe will be developed. All of these developments will make ASTEC both a European reference software for managing severe nuclear reactor accidents and a tool able to help with decision-making in crisis situations.


The CESAM project has five components:

  • the overall management of the project (managed by GRS)
  • the development, improvement and validation of the ASTEC computational models (managed by GRS)
  • the integration of the ASTEC computational models (managed by IRSN)
  • the application to nuclear facilities and the management of severe accidents (managed by JRC)
  • the dissemination of knowledge and information (managed by KIT).


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