The problem with nuclear isn't whether you can build a safe plant, you can.
The problem with nuclear is all the assumptions under which a perfectly safe plant is actually perfectly safe (proper maintenance, training, etc.).
I don't believe those assumptions always hold in practice. At the end of the day, these plants are operated by people, and private companies, who have many interests beyond keeping the plant "perfectly safe" (like making money) and also operate under constraints that prevent them from actually keeping the plant "perfectly safe" even if they wanted to (like lack of money).
The problem with nuclear isn't technological, but social. It allows a relatively small bunch of shitty people and companies to cause tremendous amounts of devastation.
Remove people from the "nuclear energy safety equation" and I'm all in with nuclear. Telling me that new plants are perfectly safe as long as people and private companies don't do shit, reads like these plants aren't safe at all to me.
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And this is without taking into account all the unknown unknowns, like all the natural disasters we can't even predict or imagine, which all plant designs just assume cannot happen.
Just claiming that modern nuclear plants are safe, for all potential world states is BS, because nobody can imagine, much less know, what all those potential world states are.
Sure coal kills people, but what makes many think its safer than nuclear is that we understand how that happens, we understand where coal goes.
See this John Oliver episode about nuclear waste. After 70 years, we haven't even been able to agree in a location to dispose nuclear waste, much less build one, and use it: https://www.youtube.com/watch?v=ZwY2E0hjGuU&list=PLMJ9OaOo9J...
All the assumptions that nuclear was safer than X over the last 70 year assumed that such a location would exist and be used.