BTW: Is this some kind of new alchemy I don't know about ? How exactly do you renew fissile or fusion-able material ?

We can probably agree that renewable is a misnomer, sine yesterday's sunlight isn't magically showing up again - it's new light from the same sun. Once the sun dims, we are in big doo-doo.

But for fission: fission end products are either useless for future energy production, or require fairly messy breeder reactors that, as I understand it, do not lend themselves to nice modularization and reconditioning that stuff isn't particularly easy (Sellafield may be a good example of how horrifyingly costly all this is). And the end fission products are never the same as the input, so I would like to understand better how you see fission as a "renewable" source.

Also, just to understand the logic in:

"Nuclear is a renewable, and of course it still makes sense to build it out."

Why? A lot of "renewables", like underwater tide plants, should probably not be built out, at least right now, because the economics are just not supporting it. Just because something is "renewable" does not automatically mean we should "of course" building it. that would be the real 70s hippie attitude we so eschew on hacker news.