The workshop will provide an overview of the Severe Accident (SA) codes, such as they exist nowadays. The bases of the research method used in the SA domain will be discussed to fully understand what is the role of SA codes in the nuclear safety arena. The description will have a generic nature and will refer to lumped parameter codes, their bases, their strengths and their drawbacks. Based on their maturity and robustness, the workshop will walk the attendee through the application of UaSA (Uncertainty and Sensitivity Analysis) in the SA domain. Along the workshop, the speaker will show plenty of examples to illustrate the major statements of the workshop.

Along the workshop, the attendee will have the chance to ask any questions at any time and will be challenged by questions raised by the own speaker to illustrate some controversies in the application of these codes.

• Background on nuclear safety (bases).
• Background on SA (a generic one sufficient).
• Familiarization with numerical analysis is optimal, but not indispensable (the workshop might be also useful for experimentalists to understand the analytical difficulties)

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By the end of the workshop, participants will:

• Know the existing predictive capability.
• Know the major drawbacks of SA codes.
• Know the challenges associated to the quantification of uncertainties.
• Be aware of the potential of the UaSA approach to enhance nuclear safety.

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• The SA research method and the current SA codes status.
• The application of UaSA.

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