Multiscale modelling in nuclear ferritic steels: from nano-sized defects to embrittlement
Abstract
Lifetime extension of existing nuclear power plants, or new builds, are efficient assets for the fight against climate change. Radiation-induced embrittlement of the steels constituting the reactor vessels, aimed at containing the radioactive fission products, is one of the main limiting factors for safe operation. In support of the fundamental understanding of the phenomena responsible for these degradations, we developed a framework that explains hardening and the subsequent embrittlement by the formation of nano-clusters of minor alloying elements. This is the first in its kind, enabling full predictability of embrittlement for any ferritic material. The core of our theory is a multiscale modelling tool that predicts the kinetics of solute clustering, given the steel chemical composition and its irradiation conditions. We prove that the formation of nano-clusters ensues from atomic transport driven by radiation-induced mechanisms that differ substantially from classical nucleation-and-growth theories. We then shown that the predicted information about solute clustering can be translated into an estimate for radiation-induced embrittlement, via standard hardening laws based on the dispersed barrier model. We demonstrate the validity of our approach by applying it to hundreds of nuclear reactors vessels from all over the world.