# Controlled irradiation hardening of tungsten by cyclic recrystallization

## TL;DR

This study investigates how cyclic recrystallization treatments, involving periodic heating, can mitigate irradiation hardening in tungsten, potentially extending the lifetime of nuclear fusion reactor components.

## Contribution

It introduces a multi-scale model to analyze microstructural evolution and demonstrates that periodic heating can significantly reduce irradiation-induced hardness in tungsten.

## Key findings

- Periodic annealing reduces hardness indicator from 140 to below 70.
- Cyclic recrystallization can control irradiation hardening effectively.
- Model predicts microstructural evolution under non-isothermal conditions.

## Abstract

The economical lifetime of the divertor is a key concern for realizing nuclear fusion reactors that may solve the world's energy problem. A main risk is thermo-mechanical failure of the plasma-facing tungsten monoblocks, as a consequence of irradiation hardening induced by neutron displacement cascades. Lifetime extensions that could be carried out without prolonged maintenance periods are desired. In this work, the effects of potential treatments for extending the lifetime of an operational reactor are explored. The proposed treatments make use of cyclic recrystallization processes that can occur in neutron-irradiated tungsten. Evolution of the microstructure under non-isothermal conditions is investigated, employing a multi-scale model that includes a physically-based mean-field recrystallization model and a cluster dynamics model for neutron irradiation effects. The model takes into account microstructural properties such as grain size and displacement-induced defect concentrations. The evolution of a hardness indicator under neutron irradiation was studied. The results reveal that, for the given microstructure and under the assumed model behaviour, periodical extra heating can have a significant positive influence on controlling the irradiation hardening. For example, at 800 C, if extra annealing at 1200 C was applied after every 100 hrs for the duration of 1 hr, then the hardness indicator reduces from maximum 140 to below 70.