3 ms·

The reasons Nuclear Fusion presents a difficult problem: 1.) There's no chain reaction mechanism. 2.) The probability of a reaction constrains reaction size.

• mschuster91 12y ago
  > Curious, anybody know how they design around this? Usually the stuff is hidden in a vacuum, which is a pretty good shield for heat.
• drjesusphd 12y ago
  > 1.) There's no chain reaction mechanism. There's something like it. Fusion happens because plasma is hot -> fusion products heat the plasma to keep it hot -> more fusion happens. A chain reaction is exactly what you don't want in a nuclear reactor. > 2.) The probability of a reaction constrains reaction size. Can you be more specific? The probability of reaction does constrain the design, but via the Lawson criterion [1]. > 3.) The absurd amount of heat generated by fusion. I think I once heard it was 100M degrees. That's about right, but temperature != heat. Even though the plasma has a very high temperature, it is also extremely diffuse: about 3 million times less dense than air. The main concern is keeping it hot in the proximity of colder stuff and managing the electromagnetic energy (the fields have many times more energy than the thermal energy, and has the potential to all be dumped in a single spot), not necessarily worrying about the heat. [1] http://en.wikipedia.org/wiki/Lawson_criterion http://en.wikipedia.org/wiki/Lawson_criterion edit: lots of silly typos