Progress in Fusion Materials for ITER
An article in Science reports on progress being made in materials used in fusion reactors, a small piece of good news for the fate of ITER. Since fusion reactors will operate at extremely high temperatures, it is critical that scientists use materials that are able to withstand such levels of heat. Researchers at the Joint European Torus (JET), the largest fusion facility in the world located in the United Kingdom, have found that using a combination of tungsten and beryllium offers better conditions to maintain a fusion reaction. This bodes well because those are the materials that are being planned for ITER, an internationally-backed fusion reactor under construction in France. From the article:
But the harsh truth is it’s not at all easy to run this fusion process in a controlled way. The current favored technique is to use a reactor called a tokamak, which employs powerful electromagnets to confine the plasma inside a doughnut-shaped reactor vessel. The magnets aim to hold the plasma away from the walls of the vessel long enough for the nuclei to fuse but plasma can often shift around in unpredictable ways. If the plasma touches the wall, this can cool it to below reaction temperature and also scour off atoms of the lining material that poison the fusion reaction. And tritium is a radioactive isotope that reactor operators have to account for very carefully. Any tritium that embeds itself in the reactor wall has to be painstakingly extracted.
The most common reactor lining, known as the first wall, in earlier fusion reactors was carbon because it is extremely resistant to high temperatures and erosion and doesn’t pollute the plasma if atoms do get into it. Carbon’s big drawback is that it’s very happy to absorb deuterium and tritium. For ITER, the first reactor to use tritium on a regular basis, absorption of tritium has to be kept to a minimum, so carbon is out.
Since no perfect material exists, the plan is to compromise and use two different materials. Most of the first wall would be coated with beryllium, which is the least plasma-polluting metal but has a low melting point if it comes into contact with the plasma.
To read the full article, click here.
