I recall that those are molten salt reactors, similar to what TerraPower now begins to construct.

https://www.ft.com/content/418907d1-d497-439c-9800-eb814226ab71

MSRs appear twice less costly than water-cooled, due to lower inherent danger in (still unlikely) case of explosion, and because of the simple fact that molten salt is used both as fuel and core coolant.

Risk of Chernobyl-fashion catastrophe with modern reactors is probably comparable to probability of Earth crust going awry and poisoning the planet with decay products, as stated in some Isaac Asimov’s works. ఠ_ఠ

However, even in those books the process resulted from a terrorist act.