Prediction of PWR thermal hydraulic margins during transient events

The regionwise point reactor kinetics (RWPRK) model is used to predict PWR core axial power distribution which is needed for calculation of fuel thermal hydraulic parameters of more importance to safety analysis during a variety of operational transients. The RWPRK model follows that of the nodal approximation method when the nodal coupling coefficients are ignored for some transient events during which the rate of change of neutrons streaming into each nodal region is slow. This kinetics model is implemented into a modified version of the COBRA-IV computer code and its performance during a variety of normal and abnormal operational transients is assessed. The transient events which are chosen for this analysis are: a partial loss of flow accident; and an unplanned decrease in secondary heat removal event. For all of these transient events, the reactor scram is intentionally delayed to make the changes in primary system state parameters which have significant feedback effects more severe