In recent years, mankind’s dependence on energy has become increasingly large. However, coal, oil and gas and other non-renewable resources, is not inexhaustible. Is it possible to solve the human energy shortage once and for all? As nuclear technology matures, controlled nuclear fusion reactors, known as “artificial sun” and “the ultimate energy of mankind”, may be able to provide clean energy for mankind continuously for the benefit of future generations.
The main principle of this technique is that thorium and thorium produce nuclear fusion reactions at high temperatures and pressures and generate large amounts of heat energy for power generation.
Recently, the team of Chen Zhangwei and Professor Lau Changshi of Shenzhen University Additive Manufacturing Research Institute, in cooperation with the Southwest Institute of Physics of the nuclear industry of China Nuclear Group (hereinafter referred to as the Southwest Institute of Physics), first proposed and realized the integrated design and forming of complex porous structure lithium silicate ceramics based on 3D printing, which is expected to replace the traditional microsphere bed structure and become a new generation of radon devices, showing an important application prospect. The results have been published in the journal Additive Manufacturing.
The radon unit is like the heart of a nuclear fusion reactor.
Since the discovery of the nuclear reaction, people have been constantly exploring the effective use of nuclear energy.
Now, more and more scientists and energy experts are looking to nuclear fusion. The raw materials for nuclear fusion are mainly the isotopes of hydrogen, thorium and thorium. Radon can be found in seawater and contains about 30 milligrams of radon per liter of water. A 1,000-megawatt nuclear substation consumes only 304 kilograms of radon per year, and by this calculation, the world’s seawater is enough for humans to use for tens of billions of years.
However, radon is almost non-existent in nature and needs to be generated by constant catalytic reactions of helium and lithium ceramics. As an important component of magnetically constrained fusion reactor, the solid-state argon cladding is one of the core problems that needs to be solved before fusion energy can be commercialized.
At present, the preferred material for thorium proliferative stomp is lithium positive silicate (Li4SiO4), and the common method is to react with lithium-for-positive silicate ceramics to helium to produce radon. Scientists refer to the ceramic components that perform this function as the radon-producing units.
Traditional lithium-ceramic radon units typically make lithium positive silicate into microspheres about 1 mm in diameter and stack them up to make them into a ball bed structure, where gaps can be injected into helium.
However, the filling rate of this type of radon-producing unit is limited and cannot be freely regulated. In addition, the stress concentration caused by microsphere accumulation is easy to cause damage such as structural deformation and cracking of the production unit, and becomes the constraint of uniform stability of the structure and performance of the ball bed.
In the event of a failure of the radon unit, the fusion reactor will not be able to operate smoothly. As a result, scientists have been trying to optimize the structure of the radon-producing units.
Another approach can greatly improve the efficiency of radon production.
In response to the above problems, in 2018, Chen Zhangwei and Lau Changshi and others, with the Southwest Institute of Physics, proposed the use of 3D printing lithium silicate ceramic unit method, the development of a new structure of the production unit.
However, the first challenge facing 3D printing is that lithium positive silicate is particularly sensitive to the environment, very easy to react with water, carbon dioxide, resulting in damage to the object, become lithium silicate.
“To this end, we from the storage of lithium silicate powder, printable powder preparation, printing process to heat treatment process, etc. , are for environmental variables for strict constraints and control. For example, the process of preparing powder slurry needs to be carried out in a glove box filled with inert gases, and all types of additives are water-free and do not react with lithium positive silicate organic solvent materials. The preparation and 3D printing of the slurry in such an environment ensures the stability of the material phase of lithium positive silicate. Professor Chen Zhangwei told Science and Technology Daily.
In order for the positive lithium silicate powder to be cured quickly after being printed in 3D, the appropriate curing forming method must be chosen.
“Ceramic 3D printing has two main curing forms, one for photocuring and the other for powder sintering or melting.” Chen Zhangwei said that powder sintering is a high-energy laser directly on the ceramic powder high-temperature sintering, sintering the desired shape, but because the temperature is relatively high, easy to produce cracking, and poor accuracy control. Optical curing not only has fewer cracking defects, high printing accuracy, but also has a strong control ability for porous structural details.
Therefore, the scientific team chose the way of photocuring and developed a special high-phase purity lithium silicate powder slurry for photocuring 3D printing.
Chen Zhangwei said: “We are mixed in the lithium silicate powder slurry mixed with the selected organic chemical additive components, as well as small doses of photosensitive additives, it is sensitive to a specific wavelength of light, the use of 405 nanometers of ultraviolet light on the slurry, can achieve the slurry of light polymerization curing.” “
3D printed out of the structural parts, and then high-temperature sintering, in the 1050 degrees Celsius environment burning 8-10 hours to achieve porcelain, you can remove the solidification structure of various additives, and no longer with the environment of water and carbon dioxide reaction, “these chemical additives are added in a physical way, will not cause damage to lithium positive silicate.” Chen explained.
The yield unit printed out by this method is an integrated defect-free structure, which has been tested to overcome the reliability problems caused by the limited filling rate of the ball bed and the stress concentration, and its stability and mechanical performance are 2 times higher than that of the traditional microsphere structure.
The 3D-printed radon-producing unit is also expected to be significantly improved in yield efficiency. The traditional microsphere structure has a duty-to-duty ratio of up to 65%, while 3D printing can be flexibly adjusted between 60% and 90%, and the ratio of lithium positive silicate is significantly increased compared to microsphere structure.
International peers highly rated the proposed 3D printing technology in the nuclear fusion core ceramic components manufacturing and application is very innovative. This research is very promising in the application of nuclear fusion reactor, which will provide more possibilities for replacing the structure of traditional ball bed ceramic radon production and promoting the commercialization of tokamak nuclear fusion reaction technology.
The trial of key components of the nuclear fusion reactor has been completed.
Although humans are a long way from controlled nuclear fusion, this does not prevent us from continuing our efforts toward semost.
As an emerging advanced manufacturing method, 3D printing subverts the traditional manufacturing model. 3D printing technology can achieve the integrated formation of complex structures, with short manufacturing cycle, high material utilization and so on, is an important innovative method of complex component manufacturing. In nuclear fusion reactors, there are also gradually shown unique advantages.
According to Professor Chen Zhangwei, the Institute of Additive Manufacturing of Shenzhen University has worked with the Southwest Institute of Physics to carry out systematic research work on the selective laser melting process (SLM, a major technical approach in metal material additive manufacturing) and its tissue performance regulation, in cooperation with the Southwest Institute of Physics. The design idea is introduced to the development of SLM forming high strength and low activation marseillated steel (RAFM, steel type developed for the future nuclear fusion reactor), based on the optimization of SLM process parameters and scanning strategy, SLM forming CLF-1 steel combines high strength and high plasticity, its comprehensive strong toughness is significantly better than the current literature reported mRAF steel.
This study provides important theoretical basis and technical guidance for the structural design of 3D-printed high-strength RAFM steel, and promotes the integrated molding of the tissue performance of key components of the nuclear fusion reactor.
According to media reports, in 2018, the Hefei Institute of Material Sciences of the Chinese Academy of Sciences has used 3D printing technology to achieve the nuclear fusion reactor key components – the first wall sample of the cladding test production.
The researchers used China’s low-activated Marsea steel (CLAM) as the raw material, printed parts sample size accuracy in line with the design requirements, the material reached a density of 99.7%, equivalent to the conventional method scored CLAM steel strength. At the same time, the study also found that 3D printing layer-by-layer melting and directional solidification characteristics led to differences in The tissue and performance of CLAM steel in different directions, which can be effectively reduced or even eliminated by scanning scheme optimization and melting pool core optimization. The research shows that 3D printing technology has good application prospect in the manufacture of complex components of advanced nuclear energy systems such as nuclear fusion reactor.
With the rapid development of basic science and the continuous change and innovation of 3D printing technology, human exploration in the field of engineering technology is full of imagination space, and it is not impossible that the components of the nuclear fusion reactor in the future are all manufactured by 3D printing.