Technically speaking, fission is defined as splitting a nucleus into large chunks, approximately half the size of the original atom.
These things use radioactive decay, which is either alpha or beta particles coming out at a constant rate. Alpha and beta decay are not considered fission. (Though you'd have a reasonable case with Beryllium-8 alpha decay to Helium-4!)
Spontaneous fission decay is a thing and does happen. But not enough to power any of these kinds of things.
These things use radioactive decay, which is either alpha or beta particles coming out at a constant rate. Alpha and beta decay are not considered fission. (Though you'd have a reasonable case with Beryllium-8 alpha decay to Helium-4!)
Spontaneous fission decay is a thing and does happen. But not enough to power any of these kinds of things.