Long-term microstructural evolution of tungsten under heat and neutron loads

TL;DR

This study investigates how tungsten's microstructure evolves under high neutron and heat loads typical of nuclear fusion reactors, revealing cyclic recrystallization and changes in irradiation hardening through multi-scale modeling.

Contribution

It introduces a combined cluster dynamics and mean-field recrystallization model to simulate tungsten's microstructural evolution under fusion-relevant conditions, including bulk nucleation effects.

Findings

Recrystallization occurs cyclically at all studied temperatures.

Irradiation hardening evolves during neutron-induced recrystallization.

Microstructural changes are predicted to impact mechanical properties.

Abstract

In nuclear fusion reactors, tungsten will be exposed to high neutron loads at high temper atures (>900 C). The evolution and degradation of the mechanical properties under these conditions is uncertain and therefore constitutes a major risk. Here, the microstructural evolution of tungsten under combined heat and neutron loads is studied, using a multi-scale approach incorporating clusters dynamics and a mean-field recrystallization model. The mean-field recrystallization model contains both nucleation in the bulk and at the grain boundaries. The cluster dynamics model includes the incorporation of loops in the dynamics of the dislocation network as a mechanism. The effects of bulk nucleation on the microstructural evolution are explored. The simulations predict a cyclically occuring neutron-induced recrystallization at all studied temperatures. Furthermore, the evolution of the irradiation hardening during neutron-induced recrystallization is assessed from the simulated microstructures.