A13-2-2 The probabilistic safety assessment

The probabilistic safety assessment (PSA) is now a companion of the SR for every new plant. In fact, after some initial doubts, it is now recognized as a valid knowledge and evaluation tool for a plant and also as valid help in the design and operation of it (see Chapter 11). It is understood, then, that PSA must be developed in parallel with the design, initially making many working assumptions on the features of the plant as it will be at the end. IAEA requirements demand that a summary of the plant PSA is included in the safety report. 

The PSA, used in this way, can be limited to level 1 or 2, that is at the first core damage or at the releases from the containment, respectively. A complete risk analysis (PRA), performed, for example, to verify the compliance of the plant with preselected risk objeetives, must also inelude level 3, that is the probabilistie evaluation of the accident consequenees. 

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