Nuclear is very sustainable. With enrichment, the world's known uranium supplies (5.5 million tons) would last about 30,000 years at present usage rates, if used with fast breeder reactors. The NEA estimates that's a sixth of what's out there. Obviously this doesn't go as far if you scale it up 10-100x, but in addition, there's about 4.5 billion tons dissolved in seawater.

This is just the uranium, not even touching the thorium. And once we get to this point, there is uranium on the Moon and Mars. The waste-management problem is harder in the political sense than the engineering sense.

> With enrichment, the world's known uranium supplies (5.5 million tons) would last about 30,000 years at present usage rates

How does it matter if you enrich or you use a natural uranium reactor? The amount of fissile material is exactly the same.

> if used with fast breeder reactors

But that's breeding, not enrichment.

> but in addition, there's about 4.5 billion tons dissolved in seawater.

...aaaand there goes your requirement for a breeder. Breeders may very well turn out not to be worth the bother.

Burning down the existing nuclear waste is a nice ability of breeders.

There's not a lot of waste to be burned anyway. If you separate U238 from the spent fuel, you don't have lot of mass left.

The big advantage of nuclear is that it is reliable. However, the paper I linked above says wind and solar can be reliable, so nuclear no longer has any redeeming qualities.

A reliable grid of nuclear + renewables is significantly cheaper than without the nuclear, according to the EU study that has been circulated here a couple months back.

The abstract for the paper (thanks for that link!) says:

> Yet even in systems which meet >90% of demand, hundreds of hours of unmet demand may occur annually.

... and the low end of the range is 72%, which leaves many more hours unaccounted for. Some amount of reliable, clean power is needed on top of the renewables.

Yes, the abstract sucks. Those are the numbers without batteries or over-building. To get to 99.99% you have to add all the mitigations: 3x overbuild, 3 hours of batteries and a continent wide grid.

A continent wide grid is easier said than done.

There’s already a lot of nuclear and hydro built!

It's a paper, not a plan. It's not saying you should switch to only wind and solar, it's that you can.

This is a proper plan: https://mitpress.mit.edu/books/electrify

It has a role for existing hydro and nuclear.

Oh sorry, I misread your original comment as saying that plan wouldn't work because it required too much overbuilding, when actually you were saying that it would work! Yes, our existing hydro and nuclear just makes it even easier to switch.