The problem with sodium cooled reactors is they are "Fast" neutron reactors. Those fast neutrons are great at making atoms of something into atoms of something else. What that means is that a very corrosion resistant alloy might be changed into something different altogether and that something might have poor anti-corrosion or pressure and high heat resistant properties and then you get a leak of hot and very radioactive sodium that burns on contact with oxygen explodes on contact with water and the smoke from such is also radioactive with a half life of 17 hours vs. radiated water that has a half life of 7 seconds. Coolant in a water cooled reactor can be mopped up safely in a couple minutes after reactor shutdown. The smoke from a fire involving irradiated sodium will be radioactive for days and could potentially spread and contaminate a much larger area. A water cooled reactor would be much better in my back yard, than a fast sodium cooled reactor.