Today's nuclear reactors can not completely fission their uranium oxide fuel rods, nor fission the transuranics produced during power generation. This waste stream is examined, and compared to that of a Thorium Molten Salt Reactor (Th-MSR) in which solid fuel rods are avoided entirely.
In a molten salt reactor, transuranics are not created at all. And the fission products can be partitioned, thanks to the fuel being in liquid form. This avoids the challenge of fission poisons appearing inside the solid uranium oxide fuel rods.
Nuclear waste is only "waste" because it has not been separated. United States 70,000 tons of nuclear waste is in a particularly difficult form for reprocessing... it is in solid form, trapped in fuel rods.
As today's nuclear industry looks to build more durable fuel rods (to withstand higher temperatures, xenon gas, and not react with water), the flip side is spent fuel will be trapped in tougher-and-tougher enclosures. This does not bode well for recycling. Instead, dissolving the fuel in molten salt offers both improved reactor safety AND easier recycling of fission products.