Engineers at the University of Wisconsin-Madison have developed a new technology that brings commercial nuclear fusion reactors one step closer.
For the fusion reaction to take place, scientists need to be able to mimic conditions comparable to the sun. At these temperatures, atoms exist in a state called a plasma – comparable to a soup of negatively charged electrons and positively charged ions that have been ripped apart by the extremely hot temperature of their surroundings.
In most fusion reactors, hydrogen atoms are used for the reaction. When they are superheated into a plasma, their single electron is ripped away, producing a soup of positive hydrogen ions and electrons. However, towards the edges of the plasma, where it is less hot, some of these hydrogen ions can bind back to the soup of electrons, creating neutralized hydrogen particles.
These neutralized particles can cause energy to be lost from the plasma, increasing the amount of energy required to maintain the reaction.
“These hydrogen neutral particles cause power losses in the plasma, which makes it very challenging to sustain a hot plasma and have an effective small fusion reactor,” Mykola Ialovega, a postdoctoral researcher in nuclear engineering and engineering physics at UW–Madison, said in a statement.
To solve this issue, the team at UW-Madison has created a spray coating mechanism that is able to mop up these problem particles while also withstanding the extreme conditions inside the nuclear reactor.
“The fusion community is urgently looking for new manufacturing approaches to economically produce large plasma-facing components in fusion reactors,” Ialovega said.
The team’s technology uses a cold spray process to deposit a coating of the metal tantalum on the stainless steel surface of the reactor. This metal can withstand the superhot temperatures of the reactor, and is also great at absorbing hydrogen.
“We discovered that the cold spray tantalum coating absorbs much more hydrogen than bulk tantalum because of the unique microstructure of the coating,” Kumar Sridharan, professor of nuclear engineering and engineering physics at UW-Madison, said in a statement.
Cold spray technology is similar to using a can of spray paint. It involves propelling particles of the coating material onto a surface at a velocity faster than the speed of sound. When they collide with the reactor walls, they flatten like squished M&Ms which forms a coating across the entire surface. However, small gaps remain between these particles, creating a larger surface area for absorbing hydrogen.