Elon uses high PITA factor when talking about why SpaceX isn't pursuing hydrogen as a rocket fuel. It similarly looks awesome on paper but results in higher TCO and higher complexity in practice. It's cheaper (according to SpaceX) to use kerosene or methane and build a bigger rocket.
For nukes vs. renewables it's likely overall cheaper to just over-build renewables and storage than to handle the long tail of pain from current-type nuclear. Spend a few billion dealing with nuclear waste, or spend a few billion on more generation and storage capacity. The former is sticky and complicated, while the latter is just straightforward commodity scaling of stuff everyone already knows how to build and handle. It's stupid and simple and scalable and if it's not enough just do more of it. In other words: just build a bigger rocket.
What I say applies to conventional and near-term fission. Fusion and other exotics might be a different ballgame. Fusion would likely be complex and high capital cost but it doesn't have the waste and "black swan failure" issues that pee in the pool for fission.