Multiscale modelling in nuclear ferritic steels: from nano-sized defects to embrittlement

TL;DR

This paper introduces a physics-based multiscale model that predicts radiation-induced embrittlement in nuclear ferritic steels by simulating nano-sized defect formation and clustering, improving safety assessments for reactor pressure vessels.

Contribution

The study presents a novel multiscale modelling approach that accurately predicts solute clustering and embrittlement in nuclear steels, surpassing traditional empirical correlations.

Findings

Model reliably predicts embrittlement across diverse materials

Accurately simulates nano-sized defect formation and clustering

Validated against data from hundreds of reactor vessels

Abstract

Radiation-induced embrittlement of nuclear steels is one of the main limiting factors for safe long-term operation of nuclear power plants. In support of accurate and safe reactor pressure vessel (RPV) lifetime assessments, we developed a physics-based model that predicts RPV steel hardening and subsequent embrittlement as a consequence of the formation of nano-sized clusters of minor alloying elements. This model is shown to provide reliable assessments of embrittlement for a very wide range of materials, with higher accuracy than industrial correlations. The core of our model is a multiscale modelling tool that predicts the kinetics of solute clustering, given the steel chemical composition and its irradiation conditions. It is based on the observation that the formation of solute clusters ensues from atomic transport driven by radiation-induced mechanisms, differently from classical nucleation-and-growth theories. We then show that the predicted information about solute clustering can be translated into a reliable 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.