Effect of gadolinium absorber radial profiling in fuel pins on VVER-1000 assembly neutron-physical characteristics

Abstract

The paper raises the problem of non-optimal use of resources. The purpose is to extend the fuel campaign. An alternative task is to increase the duration of the reactor campaign to increase the flexibility of decision-making during the operation of a nuclear reactor. The paper presents calculations of the profiling of a burnable absorber in fuel assemblies for VVER-1000 reactors. A quantitative assessment of the effect of alternative placement of gadolinium in fuel elements is made. Changes in the burnup of fuel elements in fuel assemblies are noted, as well as an advantage expressed in a change in the kinf. The results showed a strong dependence of the isotopic composition of the peripheral layer on the neutron flux density and a weak dependence of the isotopic composition of the central fuel element with gadolinium layers on the neutron flux density. The burnup when using the iterative process turned out to be impossible to align along the radius presumably due to the production of plutonium. A significant advantage of profiling a fuel cell with gadolinium is expressed in the period before the first overload, with each subsequent overload the efficiency of the technology decreases. However, kinf of the profiled assembly throughout the entire fuel campaign exceeds the kinf of the standard assembly, which indicates the efficient use of a burnable absorber.

Comparison of methods for calculating the neutronic characteristics of a VVER-1200 fuel assembly

“…The calculations were carried out using the Serpent 2 software package. The results of calculating the burnup of fuel assemblies with gadolinium for VVER-440 and VVER-1000 reactors are also presented in (Lötsch 2014, Novak et al 2017, Vnukov et al 2020. The burnup calculations for a VVER-1200 hexagonal fuel assembly (Abu Sondos et al 2019, Vnukov et al 2021) based on the Serpent code give sufficiently accurate results compared to the results obtained using other proven codes.…”