steam drillers, page-35

Opaline,
I do agree with you that it's best not to open the can of worms on the nuclear angle unless needed. Thinking of it, one can explain it as taking advantage of an existing nuclear process going on from a safe distance with no risk. And then basically say this is PRECISELY the same as solar power. Different distances, but if it's safe, it is safe. The main point to stress is that the process has been happening for millions of years as you rightly point out. After all is not all heat/energy a primary/secondary/tertiary result of nuclear forces anyhow.

The original musing followed fear of SA being covered in Radon gas (no flame required onepot :-))), and ideas of such public misinformation from say the coal lobby...

Don't know if I agree with 'true but misleading', true is true, but it's a matter of how it is raised. Perhaps it is indeed best left unsaid until asked.