Well, that isn't actually their biggest problem.

They lose efficiency of increased size for thermal generation, they won't achieve economies of scaling numbers of manufactured units, they will still require seven overlapping layers of subsidized security so will not be spread to many locations, decommissioning will likely be even more expensive than the industry experience of a billion USD per GW, and they'll still require the nuclear insurance liability cap.

The nuclear waste issue is fairly obvious just from the physics, but it's the economics that make this idea a non-starter.

For more on that, here's my article in Illuminem on the subject.

https://illuminem.com/energyvoices/c1f245f8-d201-498e-9e85-8592095ae2ac