What kind of battery backup are we talking about?

Enough for a long cold winter night in northern Europe?

Enough for a longer https://en.wikipedia.org/wiki/Dunkelflaute ?

Yes.

From your link:

"Events that last more than two days over most of Europe happen about once every five years."

I belive that for the EU as a whole, enough for two days works out as about 32 kWh per person. More or less for specific nations.

So, think in terms of what you'd repurpose used EV batteries for prior to fully recycling them.

There's no reason to believe nuear couldn't benefit from economies of scale.

Almost all nuclear plants in the west were built in the 70s and 80s. The number built since is miniscule so of course the costs are going to be huge, they're one off projects.

True but irrelevant. The construction of new reactors now is unlikely to be in numbers greater than back then.

(Unless new ones are SMR, which is why there's now business interest in SMRs. They may well have numbers large enough to cut costs).

The other issue is that nuclear research has been underfunded for decades. We could have had new safe effective and cost efficient designs.

Nuclear energy has had a massive research advantage over its entire lifetime. It simply never delivers due to being horrifically expensive.

You just keep making empty promises that never work out in reality. Just look at Flamanville 3 being 7x over budget and 13 years late on a 5 year construction schedule.

You want more of that?!?

That is why I say "might, possibly", rather than being firmly yes or no.

R&D is high-variance.

Research is, engineering less so.