This...
Cyril R wrote:
Looking at the data there's a 10x reduction every 80-100 years or so. Even with a high burnup PWR assembly, there's only a 1000 mSv/h field at 100 years, which means you get to below the treshold chronic dose of 2 mSv/day in less than 500 years. Basically you could put a 500 year old spent fuel assembly in your living room and it would pose negligible health risk!
That is a very different narrative than what we're usually fed (even by scientists in the field).
... is precisely what I got from the graph. I remember reading a "scientific" article while in high school about how linguists and archaeologists were teaming up to develop symbols to mark off our radioactive waste sites so that future civilizations won't kill themselves disturbing them. Had I known then what I know now about radioactive half life I'd have immediately known how this was not about science. I also would have more quickly realized why the magazine I read it from went out of print.
What it also tells me is that if we take out a handful of useful isotopes from the spent fuel that the radioactivity of the remains would be less than that of fresh fuel. My top four picks would be Cs-137, Sr-90, Am-241, and Np-237.
Cs-137 is a valuable radiation source in medicine and industry, such as radiation therapy and material thickness gauges.
Sr-90 can be used directly in radiothermal devices. Np-237 is a feedstock element for Pu-238 production, another valuable radiothermal element.
Am-241 is used in smoke detectors and less commonly as a radiothermal element.
If we can get enough people that won't wet themselves at the mere mention of plutonium that could also be processed out of the fuel. It's worthless for weapons as it is, too much Pu-240, but quite valuable as fuel. I don't know enough about how much Pu-239 has to be in the mix but from what I can see it looks like the plutonium processed out of the spent fuel might be suitable as seed fuel in a LFTR or similar reactor.
I'm reminded of the "rebranding" done in the coal industry. That stuff that comes out the bottom of a coal burning plant is no longer called "coal ash" or "coal waste", it's called "coal combustion products". What was once waste is now used for things like concrete aggregate and industrial abrasives. The nuclear energy industry also needs some good PR like that.