Re: No radioactivity?
No difference between helium nuclei and alpha particles, other than the energy they have, but alpha radiation is stopped by a bit of air, and as the helium nucleus slows down, it acquires two electrons from a reputable donor, turning it into delicious He, which is a good thing, because we're running awfully short of the stuff.
As to the atoms, well, the enormously high temperature makes the electrons go "I'm outta here!", leaving just the nuclei. In case of H, this is just a single proton, and in 11B, there are 5 protons and a 6 neutrons. Combine the two, as the article you linked to explains, and you end up with a single nucleus of 6 protons and 6 neutrons. These, however, are unstable for reasons far beyond my comprehension (and that of most mere mortals, top boffins excluded), and split into 3 He nuclei with 2 protons and 2 neutrons each + a rather decent amount of energy. As mentioned above, the alpha particles thus created are then slowed down and turn into lovely helium, making this almost too good to be true, if they ever manage to scale it up.