Time-dependent discontinuity factors for transient nodal models

We investigate the time dependence of discontinuity factors. First, equations for the discontinuity factors which correct finite-difference and quadratic nodal models are developed. Calculations are then performed for a coolant inlet-temperature transient and a control rod motion transient of a Westinghouse 1000 MWe PWR. These calculations demonstrate that many of the discontinuity factors may be held constant at their initial values, thus avoiding the costly task of updating the discontinuity factors during the transient. In transients involving control rod motions, however, corrections in the assemblies which contain moving control rods must be performed. (orig./DG)