A method for calculating the assembly bowing reactivity coefficients in sodium fast reactor

摘要

This paper proposed a method for the calculation of assembly bowing reactivity coefficients in sodium fast reactor. Firstly, in the core-analysis nodal method, a fuel assembly and a thin layer of sodium around it are treated as a node in the radial plane. Then the assembly bowing is discretized to radial displacements of the assembly region in each axial segment. Based on perturbation theory, the reactivity change caused by radial displacement can be expressed as the difference of reaction rates and leakage. The difference of total, scattering and fission reaction rates can be calculated by flux reconstruction and the corresponding cross sections. To take the leakage into account, this paper proposed a scheme to approximately evaluate the change of leakage by the gradient change of flux. Finally, the numerical results of the 2D and 3D problem show that this method achieves acceptable accuracy in these problems. (C) 2021 Elsevier Ltd. All rights reserved.