Karl Denninger considers the problem of energy production in a world of increasingly expensive oil and coal:
We experimented with Thorium as a nuclear fuel in the 1950s and 1960s. Carried in a molten salt there are a number of significant advantages to this fuel cycle. Chief among them is that the reactors operate at atmospheric pressure, have a strongly-negative temperature coefficient (that is, reactivity drops as temperature increases) and because they operate with their fuel dispersed in the coolant and rely on a fixed moderator in the reaction vessel shutting them down is simply a matter of draining the working fuel into a tank with sufficient surface area to dissipate decay heat. This can be accomplished passively; active cooling of a freeze plug in the bottom of the reactor vessel can be employed during normal operation and if for any reason that cooling is lost the plug melts, the coolant and working fluid drains to tanks and the reactor shuts down. In addition thorium is about as abundant in the environment as is lead, making its supply effectively infinite.A decision that might have made sense in the middle of the 1950s arms race doesn't make sense more than 60 years later. So, why aren't we utilizing thorium-based nuclear power plants?
Finally, these reactors operate at a much higher temperature; the units we have run (yes, we've built them experimentally in the 1950s - 1970s!) run in the neighborhood of 650C. This allows closed-cycle turbine systems that are more efficient than the conventional turbines in existing designs, making practical the location of reactors in places that don't have large amounts of water available. That in turn means that the risk of geological and other similar accidents (e.g. tsunamis!) is greatly reduced or eliminated. Finally, the fuel cycle is mostly-closed internally; that is, rather than requiring both fast-breeder reactors and external large-scale reprocessing plants to be practical, along with a way to store a lot of high-level waste these units burn up most of their high-level waste internally and produce their own fuel internally as well as an inherent part of their operation.
So why didn't we pursue this path for nuclear power?
That's simple: It is entirely-unsuitable for production of nuclear bombs as it produces negligible amounts of plutonium.