Frog - Nothing personal, but in the interest of minimizing the vast amount of misinformation already out there, I feel the need to deconstruct your comment:
"The so called 'Canadian' CANDU Reactors"
Not "so-called" - the CAN in the name stands for Canada, where it was conceived, designed, and developed.
http://en.wikipedia.org/wiki/CANDU_reactor "can use yellow cake (natural uranium)"
The fuel is natural (unenriched) uranium, but in the form of sintered uranium dioxide (UO2), not the refined ore known as yellowcake (mostly U3O8).
http://en.wikipedia.org/wiki/Yellowcake "thorium"
Could potentially use Th as a fertile add-on, but not stand-alone, as it is not fissile.
"old 'spent' fuel rods from light water reactors"
Reprocessing would be required, unless you are referring to DUPIC (Direct Use of spent PWR fuel In CANDU), which is still under limited development.
"(the ones that have to be kept in cooling ponds that blew up so nicely at Fukushima"
This is totally incorrect although it is a myth that was propagated by the disgraced outgoing NRC Chairman - those pools never lost inventory and are fine.
http://atomicinsights.com/2012/05/debunking-the-fukushima-spent-fuel-fable.html "can be refueled on the go"
Yes.
"can use weapons grade uranium"
Yes, after it has been blended down (unenriched).
"really the most versatile and safest reactors out there"
Maybe, but considering that fleets of LWRs have been deployed for 60 years worldwide on land and sea with no fatalities, that is a hard record to beat.
