That entirely depends on your time frame. If you're willing to wait 70 years then sure there will be economies of scale to be exploited. If you want to do it in 20 then you will have to build more highly specialized factories that produce the custom parts needed by nuclear plants. After that the factories will be useless for the next 50 years after which you need them again because the 50 year old plants are about to be decommissioned and replaced with never plants.