I'm very excited about TerraPower's Natrium reactor. It's got nothing to do with the more widely known "traveling wave" reactor. It's also not a molten salt reactor (TerraPower is working on one of those too). It's not a Thorium reactor.<p>It is a Uranium reactor that uses liquid sodium as a coolant and moderator. Sodium is known to react explosively with water, but if it's only exposed to air it burns with a mild flame that can be easily put out.<p>The main idea of Natrium is that it is a fast reactor. This has 2 major advantages: it can "burn" the U238 isotope of Uranium (which constitutes 99.7% of the Uranium in nature) and the nuclear waste contains much fewer transuranic elements, meaning it decays to the background radiation level in a matter of hundreds of years instead of millions of years.<p>Interestingly, TerraPower lists not these 2 but some other 4 major advantages on their FAQ page [1]: no need for high pressure vessels (it operates at atmospheric pressure), compact size due to the fact that sodium is exceptional at transferring heat, higher efficiency of the thermal-to-electrical conversion, by a whopping 8%, and practicality (apparently sodium is not very corrosive).<p>[1]<a href="https://natriumpower.com/frequently-asked-questions/" rel="nofollow">https://natriumpower.com/frequently-asked-questions/</a>