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I'm not a nuclear expert or anything but can you cite this? Isn't a big negative of nuclear exactly that the waste lasts for so long? What exactly does "relativ

I'm not a nuclear expert or anything but can you cite this? Isn't a big negative of nuclear exactly that the waste lasts for so long? What exactly does "relatively harmless" mean?

kemayo 8y ago
I'm too lazy to find a really good source, but here's a quick summary. The spent fuel of a nuclear power plant is a mix of various isotopes, which will decay at different rates. Nuclear decay occurs when radiation is emitted from a nucleus. Thus the more dangerously radioactive stuff decays a lot quicker. Idea is that something which is actively pumping out heat and deadly levels of radiation might become safe(-er) within a few months to years. Getting to the point of "you won't die if you spend an hour in the room with it" is still decades of waiting away, though. And the entire spent fuel mix would take thousands of years to get back to the radiation levels of the original ore we fed into the plant. All that said, a fun-ish comparison I've seen is that coal ash contains fairly high levels of heavy metals like lead and cadmium, which genuinely never become "safe". We have something like 1,500 ash disposal sites in the US which are toxic hellscapes at risk of leaking into the surrounding areas.
- village-idiot 8y ago
  Coal power plants also pump out a lot more radiation than a nuclear power plant because coal usually contains a fair bit of uranium.
- phyzome 8y ago
  « Thus the more dangerously radioactive stuff decays a lot quicker. » If it decays very quickly, yes, it's less of a threat (except in case of a spill from the reactor, where people would get exposed to fresh material.) If it decays very slowly... well, the damage just might be spread out over time. I think a case could be made for that, at least... But it's more complicated than that, anyway. Strontium, for instance, is a particular problem because it is similar to calcium, so people's bodies incorporate it into bones. Having it stick around in the body rather than flushing out makes it more dangerous than it would otherwise be. Similar for iodine, which is why nuclear meltdown preparedness programs involve having potassium iodide pills on hand—to try to saturate the body with non-radioactive iodine. So the bioaccumulation potential must be considered as well, because what matters is how long people are in contact with radioisotopes.
village-idiot 8y ago
Nuclear power plants don’t just produce “waste”, they produce uranium that’s mixed with various isotopes that don’t help sustain fission reactions. While all of this waste is “hot” the amount and makeup of the various waste product varies based on reactor design. There are two things that can be done with the waste. First, not all of the nuclear fuel is consumed. The fuel is spent when enough waste has built up to slow fission, which isn’t the same as the fuel being gone. You can re-refine spent rods to reclaim usable fuel and put it back into the reactor. Second, the real dangerous waste isotopes are the cold ones which produce a little radiation but will do so for millennia. So you can shovel those into a subcritical reactor[0] and hurry the stuff along to non-radioactive metals like lead, all while making some electricity to boot. 0: https://en.wikipedia.org/wiki/Subcritical_reactor https://en.wikipedia.org/wiki/Subcritical_reactor

I'm not a nuclear expert or anything but can you cite this? Isn't a big negative of nuclear exactly that the waste lasts for so long? What exactly does "relatively harmless" mean?

kemayo 8y ago

I'm too lazy to find a really good source, but here's a quick summary. The spent fuel of a nuclear power plant is a mix of various isotopes, which will decay at different rates. Nuclear decay occurs when radiation is emitted from a nucleus. Thus the more dangerously radioactive stuff decays a lot quicker. Idea is that something which is actively pumping out heat and deadly levels of radiation might become safe(-er) within a few months to years. Getting to the point of "you won't die if you spend an hour in the room with it" is still decades of waiting away, though. And the entire spent fuel mix would take thousands of years to get back to the radiation levels of the original ore we fed into the plant. All that said, a fun-ish comparison I've seen is that coal ash contains fairly high levels of heavy metals like lead and cadmium, which genuinely never become "safe". We have something like 1,500 ash disposal sites in the US which are toxic hellscapes at risk of leaking into the surrounding areas.

village-idiot 8y ago
Coal power plants also pump out a lot more radiation than a nuclear power plant because coal usually contains a fair bit of uranium.
phyzome 8y ago
« Thus the more dangerously radioactive stuff decays a lot quicker. » If it decays very quickly, yes, it's less of a threat (except in case of a spill from the reactor, where people would get exposed to fresh material.) If it decays very slowly... well, the damage just might be spread out over time. I think a case could be made for that, at least... But it's more complicated than that, anyway. Strontium, for instance, is a particular problem because it is similar to calcium, so people's bodies incorporate it into bones. Having it stick around in the body rather than flushing out makes it more dangerous than it would otherwise be. Similar for iodine, which is why nuclear meltdown preparedness programs involve having potassium iodide pills on hand—to try to saturate the body with non-radioactive iodine. So the bioaccumulation potential must be considered as well, because what matters is how long people are in contact with radioisotopes.

village-idiot 8y ago

Nuclear power plants don’t just produce “waste”, they produce uranium that’s mixed with various isotopes that don’t help sustain fission reactions. While all of this waste is “hot” the amount and makeup of the various waste product varies based on reactor design. There are two things that can be done with the waste. First, not all of the nuclear fuel is consumed. The fuel is spent when enough waste has built up to slow fission, which isn’t the same as the fuel being gone. You can re-refine spent rods to reclaim usable fuel and put it back into the reactor. Second, the real dangerous waste isotopes are the cold ones which produce a little radiation but will do so for millennia. So you can shovel those into a subcritical reactor[0] and hurry the stuff along to non-radioactive metals like lead, all while making some electricity to boot. 0: https://en.wikipedia.org/wiki/Subcritical_reactor https://en.wikipedia.org/wiki/Subcritical_reactor