Mathematical models in the DYN3D-FLOCAL code – consequences on reactor analysis results

The lecture gives an introduction into the computational modeling of transients in nuclear reactors. The physical models and numerical methods used in the code DYN3D for the simulation of reactivity initiated accidents in Light Water Reactors are briefly described. The importance of correct numerics for nuclear safety analysis is outlined. Examples are given, how numerical errors and not properly chosen methods can influence the results of transient analyses. Particularly, the importance of low-diffusive numerical schemes for the modelling of transport phenomena like transport of low-borated slugs of coolant is stressed.