Dependence of the product of the relative mass of fission products (burnt-up nuclides, ΔMf /M5) by the function of refueling ratio, (n+1)/n with n = NCORE/N, on enrichment of replaced FAs. Source: plotted by authors based on grid diagram data in Nuclear Fuels 2009, Xu 2003, Future of Nuclear Power 2003, Burns et al. 2020 for PWR and VVER reactors: 1 – Jatuff 2016, 2 – Semchenkov et al. 2011, 3 – Nuclear Fuels 2009, 4 – Xu 2003, 5 – approximation Xu 2003, Future of Nuclear Power 2003. Dash line: calculation based on formula (7). The polygons reflect the boundaries of the grid diagrams obtained as the result of neutron-physical calculations in Jatuff 2016, Semchenkov et al. 2011, Nuclear Fuels 2009, Xu 2003 for PWR and VVER reactors.