Current Events Of Tungsten And Molybdenum ｜ Scientists Apply Boron To Tungsten Parts in Fusion Facilities
According to Science Daily, scientists from CEA, Oak Ridge National Laboratory and France's ¦ cole Polytechnic have successfully dropped boron (B) powder into the high-temperature plasma in Tokamak, which is made of heat-resistant tungsten parts, using a powder dropper in recent research.
B What is the relationship between the element in a common household cleaner and Tokamak (annular nuclear fusion facility that heats the fuel to a high temperature of one million degrees)? The research conducted by scientists at Princeton Plasma Physics Laboratory (PPPL) of the Department of Energy (DOE) of the United States shows that the powder emitter developed by PPPL can successfully drop boron powder into the high-temperature plasma in Tokamak, and the components of Tokamak are made of a heat-resistant material called tungsten.
Scientists want to confirm that they can use this process to apply B to tungsten parts, because if the plasma damages tungsten, the exposed tungsten wall will damage the performance of the plasma.
Because of its high melting point, tungsten is increasingly used in Tokamak to help modules withstand the high heat during nuclear fusion. B partially shields the contact between tungsten and plasma, and prevents tungsten from leaking into plasma; It also absorbs any stray elements in the plasma that may come from other sources, such as oxygen. These unwanted impurities may cool the plasma and extinguish the nuclear fusion reaction.
Tungsten divertor, labmanager.com
Grant Bodner, PPPL's postdoctoral researcher, said: "We need a method to deposit boron coating without turning off the Tokamak magnetic field, and this is what the powder dropper allows us to do." He is the main author of the research paper reporting this result in Nuclear Fusion. This study was carried out using the steady state Tokamak (WEST) in the tungsten environment operated by the French Atomic Energy Commission (CEA).
Bodner added, "WEST is one of the few all tungsten environments that can help us test this technology under long pulses." Another reason physicists use WEST for experiments is that its magnets are made of superconducting materials, which will play a role in magnets in future fusion devices. This material has almost no resistance when conducting electricity, and generates little excess heat, so the magnet can operate continuously for a long time, just as the fusion reactor in the future must do. Magnets create a force that limits the plasma, enabling it to fuse.
Nuclear fusion is the power that drives the sun and stars. It combines light elements in the form of plasma - plasma is a hot, charged material state composed of free electrons and atomic nuclei - and generates a lot of energy. Scientists are seeking to replicate nuclear fusion on the earth to obtain an almost inexhaustible power supply.
Scientists need a way to supplement the B coating when the machine is running, because future nuclear fusion facilities will not be able to shut down frequently for re coating. "Putting B in Tokamak while it is running is like cleaning your apartment and doing all the other things you usually do in it, which is very helpful - it means that you don't have to take extra time out of your usual activities to do cleaning," said Alberto Gallo, a CEA scientist who contributed to the study.
The powder dripper device is mounted on the top of the Tokamak and uses an accurate actuator to move powdered materials from their storage chamber to the vacuum chamber of the Tokamak. This mechanism allows researchers to precisely set the rate and duration of powder dripping, which can include other performance enhanced materials, such as lithium, in other nuclear fusion facilities. Because of this flexibility, the burette may really play a role in the future.
Tungsten is increasingly used in Tokamak, SciTechDaily
The researchers were surprised to find that the role of boron laid by the dropper was not just to regulate the inner surface of the tungsten component. "We see that when we drop the powder, the closure of the plasma increases, which means that it retains more heat, which helps the fusion process," Bodner said
The improvement of airtightness is particularly helpful because its occurrence does not make the plasma enter a state called H-mode (high airtight mode). In this state, the airtightness is improved, but the plasma is more likely to erupt into the so-called edge positioning modes, namely ELMs. These ELMs remove heat from the plasma, reducing the efficiency of fusion reaction, and sometimes damaging internal components. Bodner said: "If we can use the dropper to obtain the good constraint of H-mode, instead of actually entering H-mode and taking the risk of ELMs, it will be very good for the fusion reactor."
"In the future, researchers hope to test and use droppers only when necessary to maintain good plasma performance. Adding any additional impurities, even boron, will reduce the fusion ability you get because the plasma becomes less pure. Therefore, we must try to use the minimum amount of boron that can still produce the effect we want." Bodner said.
