Interference effects of gaps on the energy in fuel rods in a large power reactor

One of the urgent tasks of designing the VVER-1000 fuel cycles is to account power deviations in periphery fuel rods of FAs, which are caused by in-process changes of FA form. In addition to the size of gaps between FAs, the factors that determine the power change in periphery rods is the size of adjacent gaps, and also the gap distribution about the core. The paper discusses two models: 1D reactor in four group approximation, and VVER-1000 calculated by computer code BIPR-7A. The paper discusses the calculated data and draws preliminary conclusions.