In May 2021, a good news came from the EAST fully superconducting tokamak device ("Oriental Super Ring"), a major national science and technology infrastructure in China:
The repeatable 101-second plasma operation at 120 million degrees Celsius and 20-second plasma operation at 160 million degrees Celsius was achieved, setting a new world record for the operation of the tokamak experimental device.
The nuclear fusion experimental device "Oriental Hyperloop" known as the "artificial sun" has extremely harsh operating conditions. The divertor in the device acts like the exhaust port of a car engine, through which the products of the nuclear fusion reaction need to be expelled.
The divertor is constantly subjected to the most severe high temperatures and particle streams, with transient high temperatures higher than the flame temperature of a rocket jet.
The divertor of "Oriental Super Ring" is developed by BJAT Advanced Metal Materials Technology Corporation. The divertor used in the French Superconducting Tokamak Device (WEST) is also exclusively supplied by the company, which is also a key supplier of tungsten-copper divertors for the International Thermonuclear Experimental Reactor (ITER).
Tungsten copper composite, the ideal material for divertor
Early nuclear fusion devices mainly used graphite divertors, but they could not meet the requirements of high-parameter operation. "Scientists have gradually turned their attention to tungsten, the most heat-resistant metal, and believe that tungsten-copper composite components are the most ideal choice for divertors in nuclear fusion devices." Dr. BJAT researcher. Qin said.
As the most high temperature resistant metal material, the melting point of tungsten is more than 3400 degrees Celsius, and it will melt or even volatilize under high temperature of hundreds of millions of degrees Celsius. Copper is wrapped with tungsten. Copper has strong thermal conductivity. Cooling water is used in the copper tube to quickly take away the heat. In this way, the tungsten copper composite material can withstand the impact of high temperature plasma for a long time.
How to realize the seamless connection of tungsten-copper composite is the key technical difficulty. At first, in the face of foreign technical barriers, "Oriental Super Ring" found China's leading R&D and production organization in the field of high-temperature refractory metals – BJAT, and put forward the demand for research and development of tungsten copper divertor.
Since 2008, BJAT has started the development of tungsten copper divertor.
The R&D project team gave full play to the company's technology, equipment and industrialization advantages in metal materials and metal diffusion bonding, developed the "two-step hot isostatic pressure diffusion welding" metal composite technology with independent intellectual property rights, and realized the tungsten copper composite components. High-quality dissimilar material connections.
The project team not only completed the preliminary research and development in a very short time, but also realized the mass production of high-performance tungsten materials for nuclear fusion and tungsten-copper composite components in a faster time than international counterparts.
Compound zero defect, 100% seamless connection
From material to assembly, with 108 processes, the tungsten-copper divertor developed by the project team subtly meets the stringent requirements of nuclear fusion devices.
"We have achieved zero defects in the tungsten-copper composite, which is 100% seamless. Because as long as there is one defect in the material, it will quickly lead to experimental failure in such a high temperature and harsh environment of a nuclear fusion device." Dr. Ning said. On the basis of research and development, BJAT cooperates with Chinese enterprises advanced material technology enterprises to form a complete industrial chain from material preparation, composite connection to processing and manufacturing, non-destructive testing, and is the first in the world to realize the batch production of tungsten copper divertors for fusion Production.
In 2014, "Oriental Super Ring" was the first in the world to replace the graphite divertor on the nuclear fusion device with a tungsten copper divertor. That year, the "Oriental Super Ring" set a new world record. After several years of communication and verification, in 2018, BJAT successfully won the manufacturing contract of the WEST project and began to export to Europe.