Alaska Village Moves from Diesel to 'Micro-Nuke'

"The design is described as inherently safe, but it does have one riskier feature: It uses liquid sodium, not water, to draw heat away from the core, so the heat can be used to make steam and then electricity.
Designers chose sodium so they could run the reactor about 200 degrees hotter than most power reactors, but still keep the coolant depressurized. (Water at that temperature would make steam at thousands of pounds of pressure a square inch.) The problem is that if sodium leaks, it burns."