A simple model for the study of dynamic instabilities in steam generators

Two experiments on Mercedes and 45 MW Mockups have been carried out and simulated numerically with the SICLE code. A new simple mathematical model has been derived. It consists of a set of ordinary differential equations relating inlet velocity, boiling front and two-phase residence time. An analytical study on this model permitted a better comprehension of the phenomenon of instabilities, especially the role played by the delay effect, via the two-phase residence time. The use of a numerical integration scheme permitted limit-cycles for some values of a bifurcation parameter be generated. At the end of the paper, a chaotic behaviour is generated when forcing the system. (orig.)