Become a specialist, or drive funding/regulatory pushes towards these new hardware technologies. Figure out what you see as the barriers to their commercialization, then figure out what component of that problem you'd love to work on, and become an expert in that.
My biased answer:
If you're in the position to spend a lot of time learning and experimenting with new stuff (e.g. a highschool or uni student), I'd recommend becoming an expert somewhere along the liquid fueled fission reactor stack. Chem eng, nuclear eng, rare earth extraction, uranium extraction, working with molten salts, working with liquid metals, anything like that.
If all goes well, I'll be needing people in just about every specialization there.
If you want to focus on technical skills, then you need to find a specialty that someone with good management skills will think important so that you can work with many other experts to develop things.
> If all goes well, I'll be needing people in just about every specialization there.
How far along are you in the Oak Ridge guys' elaborately detailed Molten Salt Reactor development program plan from 1974 [1], as far as it's relevant? If parts of it are irrelevant, how significant are the things you have to do that they didn't?
There are a lot of promising mostly mix-able design choices in MSRs that have become apparent in the last few decades, so we are never fully committed to a particular set.