Estimating the effect from locating spent fuel rods at the edge of the VVER-1000 reactor

Three-dimensional calculations are performed designed for optimizing the fuel configuration and usage in the WWER-1000 reactor and equalizing power distribution with a subsequent decrease in neutron leakage. The basis for the calculations involves configuring the lattice so that the peripheral row of cells contains the most highly spent rods. An elevated reactivity margin is provided for fuel burnup by minimizing the radial neutron leakage subject to the condition that the maximum value for the nonuniformity factor should be 1.35 when the reactor is run between refueling cycles. Fresh fuel is added to the inner part of the core while the outer core contains rods that have spent two cycles in the center. Data on power production and cycle length are tabulated