text: The only harmful byproduct of a hypothetical commercial nuclear fusion reactor would be a radioactive structure after a lifetime of use which is of little harm to humans. The daughter products are also much less dangerous then the products of nuclear fission and are easier to control. Unlike fission reactors, the fuel isn't stored in one large vessel. The fuel would be brought into the reactor instead of having the fuel part of the reactor. Thus, you would only have about a minute of fuel in the reactor at any given time.\n\nThe real danger with fission power plants is the fact that all that radioactive fuel is sitting there in the reactor, years worth. It's daughter products are also dangerous and unpredictable. The reason fusion plants would be less dangerous are because of the small amount of fuel used, the lack of any dangerous byproducts other then the actual reactor structure, and the relatively less dangerous (and possibly inert) reactor fuels used.\n\nOf course, there are ideal reaction methods that use nearly benign fuel and have almost no dangerous byproducts.