How do radioactive isotopes affect each other?

Obviously, there are radioactive isotopes of uranium and plutonium that affect each other. That's the basis for nuclear fission, chain reactions, nuclear reactors, and nuclear explosives. What about all the other radioactive isotopes? Aren't there 900 known naturally occurring radioactive isotopes? What effects do they have on each other, if any? Is there any research on this question, available, anywhere? Surely, by definition, radioactive isotopes release energy in some form, or other. Hence, that energy could impact on other radioactive isotopes, couldn't it? And, couldn't that interaction be interesting, or useful, at times?