Scientists have discovered what could be a significant breakthrough in the bid to find a material resistant to the radiation found inside a fusion reactor.
Currently, tungsten is the leading candidate material for the divertor or plasma-facing materials in DEMO fusion device because it has a high melting point, a good thermal conductivity and a low erosion under high heat loads. In pure tungsten, however, radiation damage at high operating temperatures results in an increase of the inherent brittleness and causes an increase in its already high ductile to brittle transition temperature.
After testing a high-entropy type of tungsten alloy (one with four or more principal elements), researchers believe this material offers the best chance yet as a suitable plasma-facing material. When exposed to irradiation at the high temperatures, the tungsten-tantalum-vanadium-chromium alloys have showed a high tolerance to radiation damage and sustainable mechanical properties after irradiation.
Involved in the project were Los Alamos National Laboratory (LANL) and Argonne National Laboratory, Pacific Northwest National Laboratory in the USA, Warsaw University of Technology, and CCFE.
The alloy was developed at LANL with CCFE staff leading the modelling team to provide a theoretical background for understanding of the exceptional radiation tolerance.
Duc Nguyen-Manh, Fusion Technology Senior Research Scientist at CCFE (pictured), said: “We undertook the modelling work at atomic level for this tungsten-based high-entropy alloys (HEAs) system within the EU/FP7 Accelerated Metallurgy project from the beginning of 2017.
“Now the model has undergone tests, it appears to have unprecedented radiation resistance.
“The scientists at Los Alamos observed that they had not encountered before a material which could withstand the level of radiation damage that this high-entropy alloy did. Our theoretical modelling combining ab-initio and Monte-Carlo techniques predicts the origin of phase decomposition within this HEA, that is consistent with the experimental results.
“The HEA showed high stability against irradiation over a wide range of temperatures and remained as the main constituent of the material even though the sample was irradiated at a high dose.”
Both experimental and modelling results were reported at the 148 TMS conference in San Antonio, Texas, March 2019.
More detailed information of this work can be found in a paper by El-Atwani et al. published in Science Advances, 2019; 5: eaav2002, 1 March 2019.