Flow-Informed Corrosion in Molten Salts using the Poisson-Nernst-Planck Model

Abstract

Molten Salt Reactors (MSRs) are a Gen-IV reactor concept which uses nuclear fuel dissolved in a molten salt as both fuel and coolant.MSRs' unique design provides enhanced safety and economic benefits, but also leads to several multiphysics effects that must be quantified and controlled: the chief of which is flow accelerated corrosion.Corrosion impacts material/barrier degradation and the mechanistic source term of nuclide transport in MSRs, which is key for their licensing and safety case bases.However, a large gap in the modeling and simulation of corrosion phenomena in MSRs still exists.In this work, we propose and compare two modeling approaches for engineering-scale modeling of corrosion in MSRs.The first approach presented is a mass transport model capturing temperature-driven species leaching and deposition between the structural materials and the molten salt.Second, a Poisson-Nernst-Planck model is presented, which models the electrochemistry of the flow-accelerated corrosion process.Verification tests checking the numerical implementation of both models are developed and presented in this article.Both models are then coupled to an engineering-scale, coarse-mesh CFD solver, which can be used to model full MSR primary loops at a moderate computational cost.The coupled system is utilized to model flow-accelerated corrosion in a natural convection loop experiment that uses FLiNaK as molten salt and 316H stainless steel as structural material.Results show good agreement between both models and the experimental measurements.This work showcases how modeling and simulation can now perform reactor-scale corrosion studies in MSRs useful for design and licensing.