1 Calculations of Coolant Flow in a VVER-440 Fuel Bundle with the Code

From the aspect of planning the power upgrading of nuclear reactors- including the VVER-440 type reactor – it is essential to get to know the flow field in the fuel assembly. For this purpose we have developed models of the fuel assembly of the VVER-440 reactor using the ANSYS CFX 10.0 CFD code. At first a 240 mm long part of a 60 degrees segment of the fuel pin bundle was modelled. Implementing this model a sensitivity study on the appropriate meshing was performed. Based on the development of the above described model, further models were built: a 960 mm long part of a 60-degree-segment and a full length part (2420 mm) of the fuel pin bundle segment. Calculations were run using the full length model to investigate a fuel assembly. In the calculations constant coolant properties and several turbulence models were applied. The impacts of choosing different turbulence models were in detail studied. For the investigated fuel assembly calculation was performed using the COBRA subchannel code too [2]. The results of the CFX and the COBRA calculations were compared. The results of the above-mentioned investigations are presented in this paper. 1