The problem with Sodium is that it violently reacts with air. Japan already experienced this with an experimental reactor that used sodium as a coolant and experienced a plumbing leak. Ended up with a difficult to put out fire. Much prefer molten salt, even though the material corrosion is more of an issue, fires do to exposure to air, is not. It's unfortunate that they turned off comments on this video, I think this is really chickenshit on their part.