CONSIDERATION OF BIFURCATIONS WITHIN THE INTERNAL ASSESSMENT OF UNCERTAINTY

摘要

The present paper deals with the problem of bifurcations in system thermohydraulics applied to the nuclear reactor safety. Non linearities in the models, use of discrete nodalisations and presence of different components and subsystems make a typical Nuclear Power Plant prone to bifurcations during the course of an accident. Bifurcations may bring the predicted working status of a system far from the actual system behaviour. The availability of a tool for the internal assessment of uncertainty made possible the present study. Making reference to a small break LOCA (Loss of Coolant Accident) in relation to which uncertainty bands were available, sources of potential bifurcation have been identified at first. Several bifurcations initial statuses have been characterised. Deterministic calculations brought to a tree of transients that may envelope all the possible 'bifurcated evolutions' of the considered system during the considered transient.