For anyone still reading, Phenix's fuel cycle (superphenix never really did anything at all except break down but it's basically the same, just a little bit higher burnup so slightly more Pu and energy at the last step).

Mine 3000t of uranium ore from Nigeria. Leave 2999t of very low level radioactive heavy-metal laden rock and sulfuric acid slurry behind in a poorly built dam for the people of Arlit to deal with.
Separate 130kg of ~4% enriched U with 5kg of U235. Leave 870kg of depleted but highly toxic and corrosive UF6 in a barrel for your grandkids to deal with.
Put the 130kg of fuel in a LWR. Get ~100TJ (140TJ in a gen iii reactor nowadays).
Separate the 1kg of Pu remaining, dump most of the Cs, Tc99 and a few other fission products into the north sea (which is still detectable in safe, but high levels in fish in Norway). This bit costs more than mining the fuel did. Radiate your own people a little with Xe-85.
"Save" the 123kg of Uranium with 1.2kg of fissile isotopes in a "strategic reserve". Nobody with a centrifuge anywhere outside of Mayak will ever enrich this because it is highly contaminated with U234, U236 and U232. It's waste. You could pretend it had 20TJ in it if you were a nukebro.
Put the 1kg of Pu in Phenix. Fission 20g of it. Get 200GJ.
Now you have 20g of super-weapons grade plutonium and 980g of plutonium that is too full of Pu240, Pu241, Pu242, Am and a few other elements to use. It's waste, nobody will ever enrich it.

Congratulations! You did a closed-loop fuel cycle! Energy solved! You have 200GJ worth of fissile material and 0.1% more energy than just using an LWR! If you did it again you could get 0.101% extra energy!

Now let's go spend the same amount as $85/W PV for the same energy output costs in 1976 on superphenix!