https://www.global.toshiba/ww/products-solutions/nuclearener...
Two Toshiba 4S reactors at the 50 MW version can cost about $3,000,000,000.
Two of those produces 100 MW.
They don't require refueling for around 30 years. $6,000,000,000 to power a 100 MW datacenter when we're talking about $500,000,000,000 is not too dramatic. Especially consider the amortized yearly cost.
That's not how you calculate these things. Check [1] for an overview, specifically Page 9. Note these metrics do not include costs to handle nuclear waste, passed over into the future (at least 1000y).
[1] https://www.lazard.com/media/gjyffoqd/lazards-lcoeplus-june-...
Maybe they could build nuclear but they could just as easily build solar with battery backup or natural gas. Lots of industrial facilities have natural gas cogeneration with the grid as a backup. If you can't get a grid connection at all due to permitting, you could just forego the backup. The reliability wouldn't be as good, but in a distributed datacenter there are ways of building in fault tolerance.
If these guys really have $500 billion, they're going to find a way to get electricity.