Note: said society is preindustrial and has ample access to flowing water, but not fossil fuels or radioactive deposits. It also has access to mountain hot springs, which I thought could also be used as “batteries” during times when streams freeze. This last point is what set him off.
He also really hates wind turbines.
Water power is pretty damn reliable, what is he on about? Water and windmills was a huge leap ahead of animal and human powered mills.
Would be kind of interesting to make an archaic nuclear reactor which is just a steam engine that kills you. But you need some pretty advanced metallurgy for that.
Naturally occurring nuclear reactors can happen, there was one that was active for a few hundred thousand years about 1.7 billion years ago in Gabon.