4 ms·

Co-60 isn't the only side product though. A quick Google search yields me https://mitnse.files.wordpress.com/2011/03/radiation_npp_07.pdf https://mitnse.files.

Co-60 isn't the only side product though. A quick Google search yields me https://mitnse.files.wordpress.com/2011/03/radiation_npp_07.pdf https://mitnse.files.wordpress.com/2011/03/radiation_npp_07.... which lists: Krypton-85 Beta/Gamma 10 years Strontium-90 Beta 28 years Iodine-131 Beta/Gamma 8 days Cesium-137 Beta/Gamma 30 years Carbon-14 Beta 5770 years Zinc-65 Beta/Gamma 245 days Cobalt-60 Beta/Gamma 5 years Iron-59 Beta/Gamma 45 days Tritium Beta 12 years I'm also not sure where you got the idea that alpha emitters are the worst kind of radioactive substance; alpha radiation is easily shielded. On the other hand, sure, just leaving the reactor there for 50 years may be part of a cost effective solution. https://www.dndkm.org/DOEKMDocuments/BestPractices/26-EFCOG%20Best%20Practice%20-%20SRS%20P%20and%20R%20Reactor%20Basins%20ISD%20Final.pdf https://www.dndkm.org/DOEKMDocuments/BestPractices/26-EFCOG%... (linked from https://en.wikipedia.org/wiki/Nuclear_decommissioning https://en.wikipedia.org/wiki/Nuclear_decommissioning) claims a 71% reduction in decomissioning costs. However, this includes neither fuel waste disposal costs nor future costs for full dismantling at some point.

belorn 7y ago
The parent talk about how the building material like rebars absorbs the isotopes, and then how long it can afterward be harmful. Do those isotopes also get absorbed, and if so, at what rate? Since I don't know the physic I don't know if all isotopes can get absorbed at the same rate, but my intuition is that the answer is no. I would also guess that nuclear plants get exposed to different amount of each type of isotope, so the above table would need to include both in order to compare the radiation risk after X years.
MrEldritch 7y ago
Alpha radiation is easily shielded from external exposure, but for that exact reason it's also the most damaging; gamma radiation, for instance, will mostly pass right through you, while alphas will deposit all of their energy right into your cells. They're shielded by your dead skin, but if you ingest or inhale them, then there's no dead skin to protect you, and all that radiation goes straight into your cells. In fact, according to the weighting system that converts joules of energy absorbed (Grays) to severity of radiation dose (Seiverts), a joule of alpha radiation is 20 times worse than a joule of X-rays, beta radiation, or gamma rays. And it's ingestion or inhalation that we're worried about from environmental contamination; not that the environment itself would become so radioactive, Fallout-style, that you'd take rads just from standing around - but that radioactive dust from demolition might get into the air, or that contaminants might leak into the groundwater.
- eqvinox 7y ago
  Yeah, but - context. We're talking about leaving a disused reactor around in some type of safe manner. Ideally it won't be leaking... but some radioactive material is still in it. Aren't the beta & gamma radiators more dangerous, even as far as irradiating other parts of the structure itself is considered?
  - MrEldritch 7y ago
    Neither beta nor gamma radiation will "activate" other parts of the structure to make them radioactive themselves; only neutron radiation (which can convert stable isotopes into unstable isotopes with more neutrons in them) can do that. Nor will they weaken the structure. So as long as people don't enter the reactor without proper precautions, there's really no reason to worry about radiation inside it. And this problem can be solved pretty well with a fence and warning signs.
    - littlestymaar 7y ago
      > So as long as people don't enter the reactor without proper precautions, there's really no reason to worry about radiation inside it. And this problem can be solved pretty well with a fence and warning signs. The buildings being designed as a bunker also helps. Just add a single guardian and his dog just to be sure nobody is actively trying to break through the concrete walls and you're good to go.
hinkley 7y ago
Isn't cesium contamination the reason why the descendants of the Bikini Islanders still can't move back to their ancestral home? Same group as potassium so it gets sucked up into fruiting bodies (eg coconuts)
- littlestymaar 7y ago
  Cs137 is a real problem, it's radioactive enough and at the same time it has a long half-life for this kind of product. And as you say, it's metabolized so it can spread through the food chain… Fortunately, it's a fission product so it's only released when you melt your reactor or when your reactor is in fact a bomb… (Mandatory reference to the Silly Asses short story from Isaac Asimov: https://en.wikipedia.org/wiki/Silly_Asses https://en.wikipedia.org/wiki/Silly_Asses).
  - hinkley 7y ago
    Then why is it listed in the grandparent as a product?
    - littlestymaar 7y ago
      Because the GP took a list that mixes both fission products and activation product. Fission products are directly created when splitting an uranium nucleus in half. They stay in the fuel rod unless it's damaged in a catastrophe. With a bomb you don't have rods, so everything is just released in the air.
xorfish 7y ago
You wouldn't leave the spent fuel in the reactor, that removes the first 5 elements. This leaves at most a 5 year halve life if you exclude water.
littlestymaar 7y ago
> I'm also not sure where you got the idea that alpha emitters are the worst kind of radioactive substance; alpha radiation is easily shielded. Ahah! I considered making an appendix especially for this one because I expected some people to make this mistake, so here we are. Notice that if you're French, the mistake isn't yours but it's the official physics course for French high-schoolers which is to blame. First of all, alpha rays are helium nucleus, they are really heavy compared to electrons (beta rays) and thus, much more energetic (energy of an order of magnitude of a few MeV vs hundreds of keV), and gamma rays in the case of radioactivity are even lower (40 keV in case of iodine for instance). If you stand in front of a radioactive source, the radiations comes from in front of you, you can really easily shield against alpha rays (because they are big!), but you can't really shield against gamma rays (because they are just photons), then gamma rays are the most dangerous in that specific context. But most people aren't physicists or nuclear workers, and you don't usually end up being irradiated by a radio source (the incident you talked about earlier is a good counter example though). The major risk faced by a population is not direct irradiation, it's contamination: that means, you eat food or drink water which contains some radioactive element. And now you get the radioactive source right in your body (let say the thyroid, if we're talking about radioactive iodine). Here, there is no possible shielding, so the total energy is what matters. And regarding the different kinds of rays and their ability to pass through matter, gamma rays have some chance to exit your body without ionizing a single cell, beta have less chance, and alpha have zero chance to go out. So yes, in terms of radio protection of populations, you fear alpha rays way more than others. And if you operated a plant you are actually allowed to release a little (and subject to regulations of course) amount of beta-emitters (tritium is released in low quantities quite often for instance) but you aren't allowed to release any single atom of alpha emitters. Also, the list you quote contains fission products (from krypton to C14) as well as activation products. Under normal conditions (I mean, no critical accident like TMI, Chernobyl or Fukushima), most fission products stays in the fuel rod, and then they won't remain in the decommissioned plant. Zn65 and Fe59 decay quickly, Tritium will be slowly released in the water nearby (yes, that's the normal procedure and it's happening during all the plant's life) and then you have Co60.
roenxi 7y ago
That list is a bit misleading for anyone skimming; it has a bunch of numbers in years and in days. I was puzzling over why there is no natural Zinc-65 until I read it more carefully.
- petre 7y ago
  Because it's gone in 10 half lives.
wbl 7y ago
The fission products are in the fuel not the primary circuit.

belorn 7y ago

The parent talk about how the building material like rebars absorbs the isotopes, and then how long it can afterward be harmful. Do those isotopes also get absorbed, and if so, at what rate? Since I don't know the physic I don't know if all isotopes can get absorbed at the same rate, but my intuition is that the answer is no. I would also guess that nuclear plants get exposed to different amount of each type of isotope, so the above table would need to include both in order to compare the radiation risk after X years.

MrEldritch 7y ago

Alpha radiation is easily shielded from external exposure, but for that exact reason it's also the most damaging; gamma radiation, for instance, will mostly pass right through you, while alphas will deposit all of their energy right into your cells. They're shielded by your dead skin, but if you ingest or inhale them, then there's no dead skin to protect you, and all that radiation goes straight into your cells. In fact, according to the weighting system that converts joules of energy absorbed (Grays) to severity of radiation dose (Seiverts), a joule of alpha radiation is 20 times worse than a joule of X-rays, beta radiation, or gamma rays. And it's ingestion or inhalation that we're worried about from environmental contamination; not that the environment itself would become so radioactive, Fallout-style, that you'd take rads just from standing around - but that radioactive dust from demolition might get into the air, or that contaminants might leak into the groundwater.

eqvinox 7y ago
Yeah, but - context. We're talking about leaving a disused reactor around in some type of safe manner. Ideally it won't be leaking... but some radioactive material is still in it. Aren't the beta & gamma radiators more dangerous, even as far as irradiating other parts of the structure itself is considered?
- MrEldritch 7y ago
  Neither beta nor gamma radiation will "activate" other parts of the structure to make them radioactive themselves; only neutron radiation (which can convert stable isotopes into unstable isotopes with more neutrons in them) can do that. Nor will they weaken the structure. So as long as people don't enter the reactor without proper precautions, there's really no reason to worry about radiation inside it. And this problem can be solved pretty well with a fence and warning signs.
  - littlestymaar 7y ago
    > So as long as people don't enter the reactor without proper precautions, there's really no reason to worry about radiation inside it. And this problem can be solved pretty well with a fence and warning signs. The buildings being designed as a bunker also helps. Just add a single guardian and his dog just to be sure nobody is actively trying to break through the concrete walls and you're good to go.

hinkley 7y ago

Isn't cesium contamination the reason why the descendants of the Bikini Islanders still can't move back to their ancestral home? Same group as potassium so it gets sucked up into fruiting bodies (eg coconuts)

littlestymaar 7y ago
Cs137 is a real problem, it's radioactive enough and at the same time it has a long half-life for this kind of product. And as you say, it's metabolized so it can spread through the food chain… Fortunately, it's a fission product so it's only released when you melt your reactor or when your reactor is in fact a bomb… (Mandatory reference to the Silly Asses short story from Isaac Asimov: https://en.wikipedia.org/wiki/Silly_Asses https://en.wikipedia.org/wiki/Silly_Asses).
- hinkley 7y ago
  Then why is it listed in the grandparent as a product?
  - littlestymaar 7y ago
    Because the GP took a list that mixes both fission products and activation product. Fission products are directly created when splitting an uranium nucleus in half. They stay in the fuel rod unless it's damaged in a catastrophe. With a bomb you don't have rods, so everything is just released in the air.

xorfish 7y ago

You wouldn't leave the spent fuel in the reactor, that removes the first 5 elements. This leaves at most a 5 year halve life if you exclude water.

littlestymaar 7y ago

> I'm also not sure where you got the idea that alpha emitters are the worst kind of radioactive substance; alpha radiation is easily shielded. Ahah! I considered making an appendix especially for this one because I expected some people to make this mistake, so here we are. Notice that if you're French, the mistake isn't yours but it's the official physics course for French high-schoolers which is to blame. First of all, alpha rays are helium nucleus, they are really heavy compared to electrons (beta rays) and thus, much more energetic (energy of an order of magnitude of a few MeV vs hundreds of keV), and gamma rays in the case of radioactivity are even lower (40 keV in case of iodine for instance). If you stand in front of a radioactive source, the radiations comes from in front of you, you can really easily shield against alpha rays (because they are big!), but you can't really shield against gamma rays (because they are just photons), then gamma rays are the most dangerous in that specific context. But most people aren't physicists or nuclear workers, and you don't usually end up being irradiated by a radio source (the incident you talked about earlier is a good counter example though). The major risk faced by a population is not direct irradiation, it's contamination: that means, you eat food or drink water which contains some radioactive element. And now you get the radioactive source right in your body (let say the thyroid, if we're talking about radioactive iodine). Here, there is no possible shielding, so the total energy is what matters. And regarding the different kinds of rays and their ability to pass through matter, gamma rays have some chance to exit your body without ionizing a single cell, beta have less chance, and alpha have zero chance to go out. So yes, in terms of radio protection of populations, you fear alpha rays way more than others. And if you operated a plant you are actually allowed to release a little (and subject to regulations of course) amount of beta-emitters (tritium is released in low quantities quite often for instance) but you aren't allowed to release any single atom of alpha emitters. Also, the list you quote contains fission products (from krypton to C14) as well as activation products. Under normal conditions (I mean, no critical accident like TMI, Chernobyl or Fukushima), most fission products stays in the fuel rod, and then they won't remain in the decommissioned plant. Zn65 and Fe59 decay quickly, Tritium will be slowly released in the water nearby (yes, that's the normal procedure and it's happening during all the plant's life) and then you have Co60.

roenxi 7y ago

That list is a bit misleading for anyone skimming; it has a bunch of numbers in years and in days. I was puzzling over why there is no natural Zinc-65 until I read it more carefully.

petre 7y ago
Because it's gone in 10 half lives.

wbl 7y ago

The fission products are in the fuel not the primary circuit.