At the beginning to the 21st century, the emergence of rapid modernization in the economies of China, India, Russia and Brazil, together representing a bit more than 30% of the global population, has increased demands for new supplies of energy. In addition, it is recognized that geometric growth of the human population on the planet could result in a 40% increase in the global population by 2050. Further, either depletion of fossil carbon resources or alteration of the global climate due to CO2 emissions will also bring additional pressures for new power sources that do not emit substan­tial quantities of greenhouse gases. These factors taken together would appear to be primary drivers for a projected expansion of the effective utilization of existing energy sources.

The single pass nuclear fuel cycle, practiced by about two-thirds of the nuclear power generating economies globally, is quite wasteful of this resource, extracting only a few percent of the energy potential of uranium (and for the moment almost none of the energy potential of thorium). At present usage levels and patterns, it is estimated there is approximately a 50 year supply of uranium available in economically recoverable mineral resources. With the application of enhanced recovery systems for uranium mineral resources, this supply could be extended (with current usage pat­terns) to about 250 years. If the nuclear component of global energy produc­tion grows (as many are projecting), these estimates are far too optimistic. It will become increasingly important to more efficiently utilize this resource through the recycle of plutonium; first to light water reactors and ultimately to a fleet of fast spectrum reactors that are capable of “burning” actinides that do not readily undergo fission in light water reactors. This will require recycling and fabrication of fuels containing a larger proportion of heavier actinide isotopes. Another advantage gained by more extensive recycle of actinides for power production will be the potential for eliminating (or at least reducing the amount of) long lived radiotoxic actinides like Am, thus improving the viability of any geologic repositories that are constructed.

To further extend the potential of this resource, it makes sense to consider the potential (an effort for the moment being led by India) of the thorium — uranium breeder reactor cycle. As thorium is three to four times more abundant than uranium, the viability of fission powered electricity is further extended by taking this step.