The fuel is non-radioactive, the process produces no radioactivity, and the residue produces no radioactivity. It is the perfect energy source. It will probably take 10 to 20 years to work out the physics of containing the reaction. There is very little He on earth, only that which was left here when the earth was formed, and some additional amount which we have made in our reactors since then. It is generated from nuclear reactions in the sun and comes to us on solar wind.
None lands on earth because it is diverted away by the earth's magnetic field.
But is does land on the moon. The moon is loaded with it. It is estimated that there is ten times as much He energy on the moon as our total historical inventory of fossil fuels.