Model predictions of dynamic instability threshold for boiling flow systems

Boiling flow systems such as boiling water nuclear reactors and once-through steam generators may be susceptible to dynamic instabilities of various types. The most common among these is a low frequency (0.1 to 2 Hz, typically) oscillatory flow instability of the limit-cycle type termed ''density-wave oscillations (DWO)''. In the present paper, two different computer models have been used to predict the DWO threshold power input for various operating conditions of an experimental system which features an electrically-heated test section assembly and water as the experimental fluid. One of the models, a frequency-domain model, has been in use for quite some time in the nuclear industry. The other is an improved version of a time-domain two-fluid model proposed by us recently