[Willie Green]

Uranium prices are so low now that it is cheaper to make new than to recycle the old.

Question about the "spent" fuel rods:

I know they still remain "hot" for many months when they're removed from the reactor and placed in 'temporary' holding tanks.

Is the heat that's given off in those holding tanks used for anything?

Can a reactor be designed to use the "spent" fuel-rods as-is?
(Yeah, I know it would be far less efficient than a "real" reactor.
But what the heck, heat is still heat!)

[Ditto]

Is the heat that's given off in those holding tanks used for anything?

Not really. It is called residual or decay heat from the short-lived fission products. It is not hot enough to produce usefull energy.

[techcor]

The invention you would like is the "Nuclear Powered Turbo-Reciprocating Engine" developed by Dr. Claudio Filippone in 1998 from the University of Maryland. There are few articles on the net if you search on google. The U.N. and the Canadian parliment have discussed it. The most readable article on the subject is in Popular Mechanics June 1998 called "Putting Nuclear Waste To Work". Has great applications in nuclear subs because the reactants can be replaced more easily than normal nuclear reactors.