Coupled Neutronics-mechanics Analysis Method for Evaluation of Reactivity Change Due to Core Distortion in Sodium Fast Reactor

Abstract

Abstract In this paper, a reactor core mechanical analysis method is introduced to provide a tool to calculate the reactivity effect of the fuel subassembly displacement in the reactor core which is an important problem for reactor types such as the Sodium-cooled Fast Reactor (SFR). The presented method relies on the following two main steps: 1) Core deformation calculation through a Computer-Aided Design (CAD) based finite element solver and 2) Static neutronic simulation on the original undeformed and deformed core models with a Mode Carlo code to quantify the reactivity effect. The technique makes it possible to accurately simulate the deformed geometry of the reactor core and to use this deformed shape model directly in the neutronic analysis. The paper includes the verification process which was conducted to compare the accuracy of the finite element solver to the theoretical solutions regarding the deformation of a hexagonal subassembly. Moreover, the neutronic calculation accuracy has been demonstrated. Following this, a validation work has been performed on the Phenix Sodium-cooled Fast Reactor based on the data obtained from previous, end-of-life test, experimental set-up. This procedure proved the accuracy of the presented methodology for both the verification and the validation cases, giving the capability to assess the reactivity effect of a non-uniform core deformation in an SFR.