"Natrium" didn't click in my head so I followed your link and worked from there. They are talking about a new variation on "fast breeder molten sodium" reactor tech. I am VERY familiar with that, one of my "minors" at Berkeley was Nuclear Engineering.

While I don't like the guy in the article he makes some good points. Nuclear is a very problematic way to go. Unless you have no other options.

People who are thinking in terms of "successor states" like B Gates are the ones pushing it.