3 ms·

What do you mean by long-lived? Fission products all become harmless ‘ less radioactive than the rocks we pulled out of the ground initially within ~300 years.

What do you mean by long-lived? Fission products all become harmless ‘ less radioactive than the rocks we pulled out of the ground initially within ~300 years. That is well within the lifetime we can design containment systems for and far too soon for language drift to become a serious problem to communicating risks. Actinides produced, ie uranium that absorbed some neutrons but didn’t fission and so became some other elements lime plutonium, americium, etc., do have half lives in the thousands to tens of thousands of years but are a much smaller fraction of the waste fuel than the fission products. They can also be put back into reactors to burn up. If you reprocess spent nuclear fuel, then you can take all the very radioactive fission products and separate them out, vitrify them, and put them somewhere. You only get about one tonne of those per GWe-yr of reactor power, and as I said, they become harmless in a few hundred years. The bulk of the remainder is U-238, which is most of nuclear fuel anyway. And the remaining ~1% or so is actinides which along with the U-238 can be mixed with fresh U-238 and U-235 to create new fuel rods which then go into reactors. Thus the only thing you really produce out of a fuel reprocessing system is the fission products, which aren’t long-lived. The only reason the US has a bunch of spent fuel with lifetimes of tens of thousands of years lying around is because we banned fuel reprocessing for no good reason in the late 70s. The entire country could run on 3TWe of nuclear power and never have more than 900k tonnes of fission products under management ever, and could be placed in a total of ~8 million tonnes of glass like the French use, taking up a volume roughly equal to a square kilometer at a depth of ~3 meters. Reference for properties of virtified waste: https://inis.iaea.org/collection/NCLCollectionStore/_Public/25/047/25047841.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/... Friendly link on waste reprocessing and properties of spent fuel: https://www.orano.group/en/unpacking-nuclear/all-about-radioactive-waste-in-france https://www.orano.group/en/unpacking-nuclear/all-about-radio...

LorenPechtel 4y ago
300 years is too short, but you've got the right idea. Let's do a little experiment. In the left corner we have a nuclear plant and reprocessing facility. In the right corner we have a coal power plant. The reprocessing facility removes the commercially useful isotopes and sells them, removes the unused uranium and plutonium and sends it to the fuel plant and sends the rest to the landfill. The coal plant sends it's fly ash to the landfill. Round 1 (one year's operation): We have waste from each powerplant, we build identical landfills. The coal plant fills it's landfill, the nuke plant only uses a small bit of it's. Round 2: The coal plant uses another landfill, the nuke plant is fine on it's original one. Round 10,000: The coal plant is on it's 10,000th landfill, the nuke plant has finally filled it's landfill. Round 10,001: The coal plant needed yet another. The nuke plant, however, we can take out the first material as it's now down to ambient (no more radioactive than an average bit of earth) and no longer a hazard. Thus we still do not need another landfill, nor will we ever.

LorenPechtel 4y ago

300 years is too short, but you've got the right idea. Let's do a little experiment. In the left corner we have a nuclear plant and reprocessing facility. In the right corner we have a coal power plant. The reprocessing facility removes the commercially useful isotopes and sells them, removes the unused uranium and plutonium and sends it to the fuel plant and sends the rest to the landfill. The coal plant sends it's fly ash to the landfill. Round 1 (one year's operation): We have waste from each powerplant, we build identical landfills. The coal plant fills it's landfill, the nuke plant only uses a small bit of it's. Round 2: The coal plant uses another landfill, the nuke plant is fine on it's original one. Round 10,000: The coal plant is on it's 10,000th landfill, the nuke plant has finally filled it's landfill. Round 10,001: The coal plant needed yet another. The nuke plant, however, we can take out the first material as it's now down to ambient (no more radioactive than an average bit of earth) and no longer a hazard. Thus we still do not need another landfill, nor will we ever.