# Effects of transmutation elements in tungsten

## TL;DR

This study investigates how transmutation elements generated in tungsten during nuclear fusion affect its mechanical properties and hydrogen/helium behavior, providing insights for its application as a plasma facing material.

## Contribution

It offers a first-principles analysis of transmutation elements' effects on tungsten's mechanical properties and H/He behavior, highlighting changes in diffusion and site preferences.

## Key findings

- Transmutation elements can enhance tungsten's ductility.
- Transmutation elements reduce H/He formation energy in tungsten.
- H/He diffusion rates increase due to transmutation elements.

## Abstract

Tungsten (W) is widely considered as the most promising plasma facing material (PFM), which will be used in nuclear fusion devices. Due to the transmutation reaction caused by the fusion neutron irradiation, transmutation elements (such as Re, Os, and Ta) are generated in the W-based PFM during the operation of nuclear fusion devices. In this paper, transmutation elements effects on mechanical properties of the W and the behavior of hydrogen/helium (H/He) atom in the W were investigated by using the first-principles calculation method. The results show that the ductility of the W is enhanced by transmutation elements if dislocation and other defects were ignored, while mechanical properties of the W incompletely depend on transmutation elements content. Compared with the pure W, the formation energy of the H/He in the W is reduced by transmutation elements, but the most favorable sites of the H/He in the W is not changed. Except for a repulsion between Ta and He in the W, the H/He in the W is attracted by transmutation elements. In addition, transmutation elements can change the best diffusion path of the H/He in the W and increase the diffusion rate of the H/He in W. This study provides a theoretical basis for the Tungsten (W) application, and further study on the effects of transmutation elements in the W will be needed.