Overview about the experimental and theoretical work on coolant mixing and analysis of hypothetical deboration transients

Experiments at the test facility ROCOM were carried out with the goal, to determine during transient processes the space-and time-dependent distribution of the coolant parameters inside the reactor pressure vessel, when differences in the boron concentration or in the coolant temperature are present at the inlet nozzles of the vessel.

  Einführung von Experimenten

Computational Fluid Dynamics (CFD) codes are intended to be applied in safety analyses of nuclear reactors. One of the possible application fields is the analysis if coolant mixing processes inside the reactor pressure vessel. Before the codes can be applied, they must undergo a validation process by pre- and post-test calculation of corresponding experiments.

  Bild Nachwuchsgruppe „CFD-Entwicklung“

For the analysis of hypothetical accidents with asymmetric perturbation of the reactor core using coupled thermal hydraulic/neutron kinetic code systems, the implementation of a model is necessary, which links the mostly one-dimensional thermal hydraulics of the system code with the two- or three-dimensional thermal hydraulics of the reactor core modeling the coolant mixing inside the reactor pressure vessel in a realistic way. Here, the development and the validation of such a model are presented.

  Einführung zu SAPR

If coolant with a too low concentration of the solute neutron absorber boron reaches the reactor core, positive reactivity is inserted, which under specific circumstances can lead to the increase of the reactor power. Amount and consequences of such an event have been analysed using the three-dimensional core model DYN3D.

  Einführung von Borverdünnungstransienten - DYN3D