Physico-statistical modelling of the primary phase of an unprotected loss of flow

Abstract : The paper presents some outlines of CEA's work on Unprotected Loss Of Flow (ULOF) using an analytical tool under development, in particular regarding boiling stabilization. It is based on analytical thermal-hydraulic models that enable very low CPU times for each simulation (compared to mechanistic tools). It will thus be used to provide large sensitivity studies on various physical parameters. In this paper, boiling stabilization possibilities are studied in the case of a low, an intermediate and a high power transient, first considering a quasi-static approach. Then, transients are simulated to highlight dynamic aspects of the problem that can't be predicted with the quasi-static approach, such as chugging phenomenon or flow excursion transients.