Annular fuel for VVER-1000 reactor: Moderation impact on neutronic behavior

Abstract

The impacts of moderation on the neutronic behavior of the VVER-1000 reactor assembly have been investigated by using annular fuel and compared with the conventional one. The study revealed that annular fuel shows a softer neutron spectrum, a better control rod worth and 16% less fissile content compared to the conventional fuel. After 60 MWd/kg burnup, annular fuel contains 6.45% and 255.41% more Pu-239 and Pu-241 respectively than the conventional fuel which can be a valuable source of fissile materials for the MOX fuel. Additionally, annular fuel shows a higher degree of symmetry in power peaking factor (PPF), higher scattering rate, 3.41% less tritium production at the beginning of cycle, and better shutdown margin without significant changes in axial & radial flux. From the neutronics point of view, annular fuel can be a propitious replacement of conventional fuel for the VVER-1000 reactor.