Robots have not proven very successful in nuclear disasters IIRC. Radiation hardening for the computers is an issue, as are manipulators and other things.

Moreover, in a disaster situation like Fukushima, power loss would be an issue. Fukushima was fine in the immediate aftermath (24 hours?) of the disaster until the on-site batteries ran out and backup generators couldn’t start due to damage from flooding. A fully robotic installation would face similar and greater problems after a SCRAM.

It’s an interesting sci-fi idea that might be possible in a hundred years, once we master simpler robots like vacuums and folding laundry!