transient calculations of coolant mixing in vver-440/213 rpv

The streamlines show the flow path of the coolant through HA in the RPV. The water goes down
directly into the core and does not mix with the warmer water in the upper plenum.
Fig. 9: Streamlines in the pressure vessel
SUMMARY
In this paper the results of three transient simulations were presented, performed in the Budapest
University of Technology and Economics, Institute of Nuclear Techniques (BME NTI). Due to
the development of the available computational capability, it is already achievable to include the
direct model of all internals in the CFD model of the pressure vessel. It opens the door to perform
detailed simulations for different transient cases.
Three different transient events were computed with the model. The performed simulations
showed that the model is applicable for the computation of different cases.
The first transient was the start up of the 6 th main coolant pump. The temperature distribution is
very inhomogeneous on the wall of the RPV at the beginning of the transient.
The second transient was the injection from the ECS into 2 nd , 3 rd and 5 th cold loops. The mass
flow of the cold water was negligible compared to the mass flow of the loops so it did not have
large influence.
The third ones was the injection from ECS into the 4 th loop and through the nozzles of HA above
the core.. The colder water fills the 4 th loop and flows into the RPV. The coolant from HA flows
down into the core and starts to cool down the fuel assemblies.