Density wave instabilities in steam generators

The aim of this paper is the stability analysis of a water-sodium straight tube steam generator (designed for Liquid Metal Fast Breeder Reactors) subjected to flow perturbations. The two phase flow dynamics is investigated and the numerical solution of the related conservation equations (mass, momentum, energy) is applied to the prediction of the steam generator response to density wave instabilities. At first, the influence of the heat flux variations is examined, then the effects of flow obstructions in some channels are determined. The results, shown in Nyquist plots, are briefly discussed. (author)