I agree with you on nuclear being more expensive as all facts point that way and future nuclear technology, but i dont understand how we could transition to a 100% renewable energy sector, It would be good if you could give a citation or explanation for that. Diverse and distributed source is how we get an energy secure grid, renewables could help with the distributed source part, but when it comes to diversity the popular renewable technologies wind and solar are very limited, both of these source cant power a base load without batteries (this applies mostly to solar, but wind too has low output at night). Also there is this issue witj managing generation and demand (Nuclear too have issue with this as its not possible to quickly adjust nuclear power generation like other conventional spurce). A full renewable energy grid would depend on batteries, currently we have much limitation with batteries. Mature technologists of acid based batteries require huge areas, and lithium based ones would require rare lithium which its mining alone would cause alot of pollution, and relying on other alt battery technology itself would be a long stretch as its development and commercialisation to usable form would take years to achieve as the same case afforable future nuclear technology.

Other alt renewable energy like geothermal could help with base load (not sure, someone could correct me if this is not the case), but itsnt possible everywhere. The same goes for tidal plant as it depends on geography and specific time of day. With this scenarios if we were to move to a 100% renewable grid then, the price for energy will increase at night time in a way that i think could reach nuclear energy rate.

A 100% renewable grid would need a lot of batteries and that too could drive the price up and possibly contribute to climate change. Also solar panel manufacturing is a very intense process with a lot of carbon impact, i read this on a text during my academics (havent checked the source for this other than that).