Transverse Transport and Heat Transfer in Smooth VVER Fuel-Rod Bundle with Cellular Spacer Grid

The results of the numerical modeling of flow and heat transfer in a bundle of smooth fuel rods spaced by a cellular grid in application to VVER are presented. The results are analyzed and compared with computational-experimental studies in the homegrown and foreign nuclear power industries. The computational region simulating a VVER FA fragment, a mathematical model, and the boundary conditions are described. The results of a calculation of the coolant flow velocity field and the temperature field for the fuel-rod cladding under conditions of stabilized heat transfer in the bundle and on a section of stabilization beyond the cellular spacer grid are presented. Flow in the bundle and the mechanisms of interchannel transfer are described. Recommendations are given for taking account of the grid effect on intensification of heat transfer in the bundle, and a comparison is made with data obtained for plate-shaped spacer grids in PWR.