AMADEUS: deterministic calculus support to the probabilistic safety analysis of nuclear power plant Atucha 1

The AMADEUS code, which is a first-principles thermalhydraulic code, is intend to facilitate the comprehension of the transients without loss of coolant dynamics. Being fast and user-friendly, allows to calculate transients with either single or combined failures, and to perform parametric studies. AMADEUS has proven to be very useful to develop event sequences, to postulate success criteria, and to estimate the periods of time in which countermeasures are required. Sequences which resulted in a high failure probability were reevaluated with more sophisticated and internationally accepted codes, such as RELAP, and very good agreement was observed. Some of these transients are presented, showing the complicated physics managed by the code and how it helped analysts to develop accident sequences. 3 refs., 12 figs