4 ms·

Can anyone explain to me why this would be preferred over the alternative they mention in the article of evaporating the water?

garmaine 5y ago
The radioactive water still goes somewhere. Would you rather it go into the ocean or into our lungs and crops?
- asymmetric 5y ago
  You seem to imply the ocean is a clearly better option — I’m not sure it is? Harm will come to us and other animals either way, the extent seems a bit hard to assess and depends highly on what one values.
  - eganist 5y ago
    The water can stop beta particles far more effectively than the air (2in v. 10ft), which minimizes the risk to life forms save for those which directly interact with tritium water, but even then, there's far more water in the ocean for tritium water to dilute into. In the air, the water will still get invariably pulled into the water cycle, wherein it condenses into rain, enters streams and lakes, plants, life, etc. where it can't as effectively dilute. Would love for a nuclear or environmental researcher to fact-check me here. I'm out of my depth. I'm just applying the trivia that I know.
    - skrause 5y ago
      This "what if" xkcd is somewhat relevant: https://what-if.xkcd.com/74/ https://what-if.xkcd.com/74/ The vast majority of water molecules in the oceans have never been drunk by any human ever.
    - rnhmjoj 5y ago
      I'm just a physics student by incidentally I'm researching tritium right now. Tritium is one of the least toxic radionuclide because the β radiation it emits is very low energy, also the biological half life is only 10 days (it means it's quickly eliminated by the body): unless you ingest very large quantities of it, you're probably going to be fine. In fact, the range of the electrons is even less than you quote: around 5 mm in air and 6 μm in water, which means it's effectively stopped by the dead skin layer. If I were to decide, I would probably pick dilution in water over vaporisation.
      - eganist 5y ago
        > around 5 mm in air and 6 μm in water Interesting. My source re: beta radiation was (admittedly a nuclear promotion nonprofit) http://nuclearconnect.org/know-nuclear/science/protecting http://nuclearconnect.org/know-nuclear/science/protecting > β BETA – can only be stopped after traveling through about 10 feet of air, less than 2 inches of water, or a thin layer of glass or metal. Additional covering, for example heavy clothing, is necessary to protect against beta-emitters. Some beta particles can penetrate and burn the skin. I won't be surprised if you're right, but if a nonprofit getting government grants to promote the nuclear industry gets it wrong, I'd be pretty worried.
        ascar 5y ago
        The problem is that the source is generalizing, which is fine for saying beta has usually shorter range and is less dangerous than gamma, but is too general to be applicable here. Beta radiation just describes a certain kind of radiation, namely emitting an electron (or positron). However it doesn't directly tell you how much energy that electron has. Wikipedia on Beta particles says that "Beta particles with an energy of 0.5 MeV have a range of about one metre in air; the distance is dependent on the particle energy." [1] Tritium beta decay just has an energy of 0.018590 MeV [2] and I wouldn't be surprised if reach isn't proportional but for example cubic (I don't know the formula) thus the huge difference in reach. [1] https://en.m.wikipedia.org/wiki/Beta_particle#:~:text=Beta%20particles%20with%20an%20energy,less%20ionising%20than%20alpha%20particles https://en.m.wikipedia.org/wiki/Beta_particle#:~:text=Beta%2.... [2] https://en.m.wikipedia.org/wiki/Tritium https://en.m.wikipedia.org/wiki/Tritium
        eganist 5y ago
        Helpful, thanks!
        perpetualpatzer 5y ago
        My understanding is that penetration depends on the energy associated with the the β particle [0] and tritium decay releases relatively lower-energy β particles [1]. The nonprofit isn't wrong... they're just saying "a .22 bullet can kill you" while parent is saying "tritium is like throwing the bullet instead of firing." [1] https://sciencedemonstrations.fas.harvard.edu/presentations/%CE%B1-%CE%B2-%CE%B3-penetration-and-shielding https://sciencedemonstrations.fas.harvard.edu/presentations/... [1] https://en.wikipedia.org/wiki/Tritium https://en.wikipedia.org/wiki/Tritium
  - ddingus 5y ago
    Harm was going to come to us, post event, no matter what. Some argue we are not good enough at these things, meaning harm will come to us every time we generate energy this way. The only real question being us or future people, near or longer term harm. Say we set that aside as a matter of ambiguity and just focus on type of harm. (My own take is we will generate energy this way, so we may as well fund serious risk mitigation of all kinds.) We have only one option here longer term, and that is dilution. Normally, we have two, the other being containment. (And, given we do make energy this way, strong investment in containment makes a lot of sense.) And in this scenario, we have both contaminated water to deal with and a core likely to enter the water cycle itself at some point too. It will, at that time, irradiate water for a long time. Is the harm in the atmosphere greater than in water? It will go somewhere. IMHO, the water is a better shield and has far greater capacity to serve as a medium to dilute in than the air does.
  - garmaine 5y ago
    The ocean is clearly a better option. First, water itself acts as an absorbent of the emitted radiation. So the only living things which take up the radiation are those which consume the water. Second, unlike heavy metals, the uptake of heavy water isn't especially driven by biology. They don't soak up and concentrate the radiation. Third, there is a lot more water in the ocean than the atmosphere. In the ocean it will dilute to nearly unmeasurable levels. In the atmosphere it will fall back down as rain and concentrate in our water supply, irrigation, and crops.
- busymom0 5y ago
  I am uneducated at the science behind it but wouldn’t evaporating method only result in the water being evaporated and not the “radioactive stuff” in it? Similar to how Bear Gryls would evaporate urine to make clean drinkable water.
  - DuskStar 5y ago
    The radioactive stuff is still chemically water.
  - garmaine 5y ago
    The radioactive stuff in it is the water. This is super-heavy-water, formed with tritium instead of "normal" hydrogen. It's already been filtered to remove all other (radioactive) contaminants. There is no cost effective way to filter out the heavy water from regular water at the scale required though.
etiam 5y ago
Not sure how much it matters for the difference in risks after dilution, but beta radiation probably has short reach in water compared to air. From the perspective of the people releasing the radioactive water, evaporating it would give them larger volumes of a material that is more difficult to manage before it disperses and in medium where more of the radiation reaches further. Seems like the main environmental concern ought to be absorption into tissues though, and it's not at all clear to me that highly active marine ecosystems with long food chains is the preferable alternative there.
kenned3 5y ago
you would need a tritium refinement plant, like what we have in Ontario. Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron. This reaction has a quite small absorption cross section, making heavy water a good neutron moderator, and relatively little tritium is produced. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. Ontario Power Generation's "Tritium Removal Facility" processes up to 2,500 tonnes (2,500 long tons; 2,800 short tons) of heavy water a year, and it separates out about 2.5 kg (5.5 lb) of tritium, making it available for other uses.[13] you dont really want to just "evaporate the water" but "distill" it, same as making alcohol... the boiling points are very close and it is expensive to process that much water.
- akadruid1 5y ago
  There's a longer article linked from this one which says Fukushima is generating 140 tons of contaminated water per day and has well over a million tons stored. Not sure if it's measuring the same thing but it seems they might need a much larger scale facility.

garmaine 5y ago

The radioactive water still goes somewhere. Would you rather it go into the ocean or into our lungs and crops?

asymmetric 5y ago
You seem to imply the ocean is a clearly better option — I’m not sure it is? Harm will come to us and other animals either way, the extent seems a bit hard to assess and depends highly on what one values.
- eganist 5y ago
  The water can stop beta particles far more effectively than the air (2in v. 10ft), which minimizes the risk to life forms save for those which directly interact with tritium water, but even then, there's far more water in the ocean for tritium water to dilute into. In the air, the water will still get invariably pulled into the water cycle, wherein it condenses into rain, enters streams and lakes, plants, life, etc. where it can't as effectively dilute. Would love for a nuclear or environmental researcher to fact-check me here. I'm out of my depth. I'm just applying the trivia that I know.
  - skrause 5y ago
    This "what if" xkcd is somewhat relevant: https://what-if.xkcd.com/74/ https://what-if.xkcd.com/74/ The vast majority of water molecules in the oceans have never been drunk by any human ever.
  - rnhmjoj 5y ago
    I'm just a physics student by incidentally I'm researching tritium right now. Tritium is one of the least toxic radionuclide because the β radiation it emits is very low energy, also the biological half life is only 10 days (it means it's quickly eliminated by the body): unless you ingest very large quantities of it, you're probably going to be fine. In fact, the range of the electrons is even less than you quote: around 5 mm in air and 6 μm in water, which means it's effectively stopped by the dead skin layer. If I were to decide, I would probably pick dilution in water over vaporisation.
    - eganist 5y ago
      > around 5 mm in air and 6 μm in water Interesting. My source re: beta radiation was (admittedly a nuclear promotion nonprofit) http://nuclearconnect.org/know-nuclear/science/protecting http://nuclearconnect.org/know-nuclear/science/protecting > β BETA – can only be stopped after traveling through about 10 feet of air, less than 2 inches of water, or a thin layer of glass or metal. Additional covering, for example heavy clothing, is necessary to protect against beta-emitters. Some beta particles can penetrate and burn the skin. I won't be surprised if you're right, but if a nonprofit getting government grants to promote the nuclear industry gets it wrong, I'd be pretty worried.
      - ascar 5y ago
        The problem is that the source is generalizing, which is fine for saying beta has usually shorter range and is less dangerous than gamma, but is too general to be applicable here. Beta radiation just describes a certain kind of radiation, namely emitting an electron (or positron). However it doesn't directly tell you how much energy that electron has. Wikipedia on Beta particles says that "Beta particles with an energy of 0.5 MeV have a range of about one metre in air; the distance is dependent on the particle energy." [1] Tritium beta decay just has an energy of 0.018590 MeV [2] and I wouldn't be surprised if reach isn't proportional but for example cubic (I don't know the formula) thus the huge difference in reach. [1] https://en.m.wikipedia.org/wiki/Beta_particle#:~:text=Beta%20particles%20with%20an%20energy,less%20ionising%20than%20alpha%20particles https://en.m.wikipedia.org/wiki/Beta_particle#:~:text=Beta%2.... [2] https://en.m.wikipedia.org/wiki/Tritium https://en.m.wikipedia.org/wiki/Tritium
        eganist 5y ago
        Helpful, thanks!
      - perpetualpatzer 5y ago
        My understanding is that penetration depends on the energy associated with the the β particle [0] and tritium decay releases relatively lower-energy β particles [1]. The nonprofit isn't wrong... they're just saying "a .22 bullet can kill you" while parent is saying "tritium is like throwing the bullet instead of firing." [1] https://sciencedemonstrations.fas.harvard.edu/presentations/%CE%B1-%CE%B2-%CE%B3-penetration-and-shielding https://sciencedemonstrations.fas.harvard.edu/presentations/... [1] https://en.wikipedia.org/wiki/Tritium https://en.wikipedia.org/wiki/Tritium
- ddingus 5y ago
  Harm was going to come to us, post event, no matter what. Some argue we are not good enough at these things, meaning harm will come to us every time we generate energy this way. The only real question being us or future people, near or longer term harm. Say we set that aside as a matter of ambiguity and just focus on type of harm. (My own take is we will generate energy this way, so we may as well fund serious risk mitigation of all kinds.) We have only one option here longer term, and that is dilution. Normally, we have two, the other being containment. (And, given we do make energy this way, strong investment in containment makes a lot of sense.) And in this scenario, we have both contaminated water to deal with and a core likely to enter the water cycle itself at some point too. It will, at that time, irradiate water for a long time. Is the harm in the atmosphere greater than in water? It will go somewhere. IMHO, the water is a better shield and has far greater capacity to serve as a medium to dilute in than the air does.
- garmaine 5y ago
  The ocean is clearly a better option. First, water itself acts as an absorbent of the emitted radiation. So the only living things which take up the radiation are those which consume the water. Second, unlike heavy metals, the uptake of heavy water isn't especially driven by biology. They don't soak up and concentrate the radiation. Third, there is a lot more water in the ocean than the atmosphere. In the ocean it will dilute to nearly unmeasurable levels. In the atmosphere it will fall back down as rain and concentrate in our water supply, irrigation, and crops.
busymom0 5y ago
I am uneducated at the science behind it but wouldn’t evaporating method only result in the water being evaporated and not the “radioactive stuff” in it? Similar to how Bear Gryls would evaporate urine to make clean drinkable water.
- DuskStar 5y ago
  The radioactive stuff is still chemically water.
- garmaine 5y ago
  The radioactive stuff in it is the water. This is super-heavy-water, formed with tritium instead of "normal" hydrogen. It's already been filtered to remove all other (radioactive) contaminants. There is no cost effective way to filter out the heavy water from regular water at the scale required though.

etiam 5y ago

Not sure how much it matters for the difference in risks after dilution, but beta radiation probably has short reach in water compared to air. From the perspective of the people releasing the radioactive water, evaporating it would give them larger volumes of a material that is more difficult to manage before it disperses and in medium where more of the radiation reaches further. Seems like the main environmental concern ought to be absorption into tissues though, and it's not at all clear to me that highly active marine ecosystems with long food chains is the preferable alternative there.

kenned3 5y ago

you would need a tritium refinement plant, like what we have in Ontario. Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron. This reaction has a quite small absorption cross section, making heavy water a good neutron moderator, and relatively little tritium is produced. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. Ontario Power Generation's "Tritium Removal Facility" processes up to 2,500 tonnes (2,500 long tons; 2,800 short tons) of heavy water a year, and it separates out about 2.5 kg (5.5 lb) of tritium, making it available for other uses.[13] you dont really want to just "evaporate the water" but "distill" it, same as making alcohol... the boiling points are very close and it is expensive to process that much water.

akadruid1 5y ago
There's a longer article linked from this one which says Fukushima is generating 140 tons of contaminated water per day and has well over a million tons stored. Not sure if it's measuring the same thing but it seems they might need a much larger scale facility.