3D numerical investigation of natural circulation between the reactor pressure vessel and the cooling pond of a VVER-440 type reactor in incidental conditions during maintenance

Abstract

Abstract During the annual maintenance of the VVER-440 type reactors, the reactor pressure vessel, the cooling pond and the transfer pond form a connected flow domain. The reactor is cooled by the natural circulation, which develops in one or two main loops. The cooling pond has its own cooling loops. CFD calculations have been performed with the code CFX-4.3 to investigate whether it is possible to cool the reactor core in case the main loops are lost and other emergency systems are not available. The results point out that the cooling system of the cooling pond is not capable of cooling the reactor core with the present connection. Therefore, modifications of the cooling system are investigated which would make it suitable for removing the remanent heat from the core.