Analysis of flow instabilities at the natural circulation loop DANTON withregard to non-linear effects

The natural circulation loop DANTON at the Dresden University of Technology was designed to investigate the thermohydraulic properties of integrated r eactor concepts with a natural circulation driven primary loop. It is not p ossible to reach a stable two-phase flow in the loop without passing flow i nstabilities. At an equilibrium of heating and cooling power the flow oscil lations can exist at nearly constant frequencies and amplitudes. The oscill ating mass flow signal had been investigated by various methods: (a) autoco rrelation function, (b) Fast Fourier transformation, (c) estimation of a te mporal Liapunov-exponent and (d) reconstruction of the system attractor in a three-dimensional phase space. The selected time-series express a non-lin ear behaviour, however, they are not chaotic. In comparison to the usual me thods the applied analysing methods yield additional information about syst em frequencies, sensitiveness to disturbances and properties due to non-lin ear and chaotic behaviour in a natural circulation loop.