Regional Basic Professional Training Course in Korea

Regional Basic Professional Training Course (BPTC) on Nuclear Safety
The major inconvenient is that the dynamic aspects cannot be treated without
approximations that are difficult to justify.
9.3.6.3. Other methods
Other interesting methods can also be used and developments are still in progress. It is
possible to use, for example, the state graphs (generally Markov graphs), the Petri-nets,
and the Monte-Carlo simulation. These methods can be used for the systems modelling,
as well as for the sequences modelling. The main goal is to account for various specific
operating aspects, especially temporal dependencies. On the contrary, these methods are
generally more complex, time consuming and difficult to interpret. For these reasons they
are presently limited to particular cases, and especially to validate approximations
introduced in a simplified model.
9.3.7. Uncertainty analysis
Qualitative discussion and quantitative measure of uncertainties in the PSA results is a
very important task. Uncertainty estimation is particularly important for the analysis of
risk contributions, for decision-making, and for the credibility of the results.
Since the PSA model attempts to simulate reality, it is inevitable that there will be
simplifying assumptions of rather complex phenomena that generate uncertainties. Three
major categories of sources of uncertainties can be identified:
Completeness. Although the aim of the PSA model is to be as complete as possible,
there is no guarantee that this process can ever be complete and that all possible
scenarios have been identified and quantified. This lack of completeness introduces
an uncertainty that is particularly difficult to assess.
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