Partial depletion of the primary circuit during a postulated small break loss of coolant accident can lead to the interruption of one-phase flow natural circulation. In this case, the decay heat is removed from the core in the reflux-condenser mode. In case of the partial non-availability of the safety injection system, weakly borated condensate can accumulate in particular in the pump loop sea...

A nonlinear dynamic model for natural circulation drum-boilers is presented. The model describes the complicated dynamics of the drum, downcomer, and riser components. It is derived from "rst principles, and is characterized by a few physical parameters. A strong e!ort has been made to strike a balance between "delity and simplicity. Results from validation of the model against unique plant dat...