An image like this is perhaps a perfect example to illuistrate why your radioactive heating idea is seriously flawed.

Now please bear in mind, I'm not trying to make this personal so let's try to keep this civil, lest we burst into flames, ok?

Anyway, this picture shows a huge number of energetic charged particles(radiation), mostly protons and electrons, expending their energy into the upper atmosphere where it is very rarified, something like a millionth of an atmosphere.

And you can see from the visible light emission that the particles don't penetrate that far in what is essentially a vacuum.

What do ya think?