I would like to take this moment to say I agree wholeheartedly with what Sam Stone is saying, despite normally being of opposing opinion.
Been away for a week so this is a bit of a bump, but I wanted to comment on this. It depends what aspect of the spent fuel you’re looking at, and what detrimental effects you’re considering.
The fission products, i.e. the new, light atoms formed when the uranium and/or plutonium atoms fragment, do indeed decay to natural level of radioactivity within around 500-1000 years, as shown on the graph you referenced. This is because after 1000 years these highly radioactive elements are GONE, they have all decayed to stable elements. At this stage you should be able to stand next to the spent fuel rods, touch them if their claddings are intact, or hold the spent fuel itself if it’s not in an inhalable form and you wear gloves. (You’ll almost certainly be okay even if you don’t.)
After 1000 years, the spent fuel will consist mostly of uranium 238, plus the stable elements of fission product decay (Strontium 90 for example will have decayed to zirconium), plus a small quantity of transmutation products. Transmutation products are the new heavy elements formed by neutron capture while the rods were in use (graphed as “activation products” in your cite.) Table A3-1 shows they are mainly plutonium isotopes. Because of them, the spent fuel WILL be considerably more radioactive than natural uranium, and will remain so for a million years. But both natural uranium and 1000-year old spent fuel are alpha-emitters, so in terms of handling and external exposure, they are roughly equally hazardous. I.e., not very.
Natural uranium is a weak alpha emitter; even if ingested it is more hazardous as a heavy metal than anything else. The transmutation products are stronger alpha emitters which makes them radiological toxins, but provided they’re not inhaled and retained in the lungs, or ingested and absorbed, they simply aren’t hazardous. The points in italics are important because it’s actually quite hard to retain particles of anything in the lungs - our bodies are rather good at getting rid of them. Particles of the right size and shape to stick in your lungs are hazardous whether they’re radioactive or not. And plutonium isn’t that easy for your body to absorb orally.
If the spent fuel rods have been reprocessed, the tranmutation products will have been extracted anyway. There is also the possibility of “burning” them away by neutron bombardment, or greatly reducing their production using altered reactor designs. But none of this is really necessary. Incorporate the spent fuel into ceramic or glass blocks, and store them for a thousand years, and you could probably build your house out of them safely. Yes, they’ll be radioactive, but not enough to worry about.
Incidentally, I am highly skeptical of table A3-3 on pg 344. I suspect the figures have been generated by simply taking the projected material activity in Bq and applying an inverse-square law for dosage. This neglects the fact that the radioactivity will be almost exclusively alpha-emissions after 1000 years, and alpha is simply not penetrating enough to worry about from an external source. (Unless by “unshielded”, they mean the fuel won’t block its own alpha emissions, there is only vacuum between the fuel and the exposee, and the exposee has no skin. Which they might.)
Sure, there’s some serious risks with with nuclear power. Chernobyl comes to mind. The only serious nuclear plant disaster in 50 years, and there is currently over 400 operating in the world
But which was more of a disaster? Katrina or Chernobyl? A couple of dozen lives lost in Katrina while at least a thousand died on the delta. Seems no one is too worried that they’re rebuilding New Orleans.
The irony is, that nulear power to manufacture polution free mobile fuel is the best way to mitigate AGW and forestall the inevitable rising sea level that is certain to inundate New Orleans again.