7 ms·

These robots are radiation hardened, and the levels of radiation are steadily decreasing. At some point it will inevitably become survivable.

by jjk166 2y ago

johnea 2y ago
Exactly! we just need to try again in 10,000 years...
- BurningFrog 2y ago
  I don't know the numbers, but it's much less! Because if an isotope emits high radiation, it will "burn out" relatively fast. If it lasts thousands of years, it does it by emitting low radiation. And, yes, I know this is a serious comment to sarcasm, but I feel educational today...
  - lainga 2y ago
    See the 7-10 rule (of murky and apparently empirical provenance), although this is for fission products of a bomb, not melted fuel https://physics.stackexchange.com/questions/336049/can-the-7-10-rule-of-thumb-for-radiation-be-understood-theoretically https://physics.stackexchange.com/questions/336049/can-the-7...
  - godelski 2y ago
    > Because if an isotope emits high radiation, it will "burn out" relatively fast > but I feel educational today... To help people get intuition about this remember that energy is conserved. Radiation can come in multiple forms: alpha (2 protons and 2 neutrons), beta (electron or positron), or gamma (high energy "light"). At each decay even the original atom MUST lose energy, and thus, mass (thanks Einstein!). Alpha is pretty common (how Uranium-238 decays into Thorium-234, in 4.4e9 years, releasing 4.2 MeV of energy[0]). But also note that this is large and that's why it can be stopped pretty easily (unless the MeV is very high). Beta decay is a bit trickier because it can be either a positron or electron, but the process is quite similar. In both alpha and beta decay there's a clear mass being ejected from the atom (and along with it, energy). An example of beta decay is when Thorium-234 decays into Protactinium-234m (m for "metastable") in 24.1 days but with only 0.27MeV (you can tell here thought that this decay releases more energy over time, despite being a lower amount of energy released per decay event). Protactinium-234m then has a VERY short half-life of 1.16 minutes releasing 2.27MeV per event, turning into Protactinium-234, which also has a short half-life of 6.7 hrs, giving off 2.2 MeV of beta- (electron) decay, turning into Uranium-234, which has a long half-life of 2.45e5 years. I think this last example is where people get confused, because we went from Uranium to Uranium, right? But the numbers are important! Uranium-238 to Uranium-234! Those are the number of neutrons in each atom. Uranium-234 is much more stable. (I need to also note that there are some long lived products with high energies, but this is far more complicated than we have time for in this already long comment. We'd have to also discuss biological half-lives if we're going to talk about that. And someone will mention stuff about boars and mushrooms, and not understand) The other confusing part is waste and composition of waste[1]. It's important to note that 90% of waste is "low level", which are things like clothing or tools, and only contain 1% of the total radiation in waste. This stuff is readily disposed of, and the truth here is that were this to all get lost, there would be no real serious danger posed to any{one,thing}. We like to be on the safe side with nuclear, and for good reason (this is again, complicated). But the AMOUNT of waste is __VERY__ little > On average, the waste from a reactor supplying a person’s electricity needs for a year would be about the size of a brick. Only 5 grams of this is high-level waste – about the same weight as a sheet of paper. And, > Unlike any other energy generating industry, the nuclear sector takes full responsibility for all of its waste. So this needs to be remembered when comparing competing energies. This is a common misconception when comparing and people without actual domain expertise here naively look at data and don't understand the assumptions of that data (I'm looking at us, HN...). And it is more complicated than just comparing the full waste generation from solar vs nuclear (as a far too common example. Which these technologies don't compete!) So TLDR: The decay can be simply thought of as "high energy, short lived" while the rest is actually incredibly complicated and exceptional levels of nuance are required for actually making good comparisons. This last part isn't isolated to nuclear technologies and is a common logic failure of many internet warriors. TTLDR: shit is complicated, don't talk about complicated stuff if you're passion doesn't align with your efforts to educate yourself and understand the nuance. [0] https://en.wikipedia.org/wiki/Decay_chain#Uranium_series https://en.wikipedia.org/wiki/Decay_chain#Uranium_series [1] https://world-nuclear.org/nuclear-essentials/what-is-nuclear-waste-and-what-do-we-do-with-it https://world-nuclear.org/nuclear-essentials/what-is-nuclear...
    - jrflowers 2y ago
      I like this comment because it can be summed up as “You are pretty much correct, also I am smarter than you are”
      - godelski 2y ago
        Definitely not. I have no idea how much BurningFrog knows or not. I was just continuing their education. Expanding on their comment, no more. Don't always assume malicious behavior. We're nerds. Sometimes we just get excited to talk about things we've sunken thousands of hours of our lives learning and get excited thinking others might also be excited with this thing we find cool. I hope there are things you get a lot of joy thinking about and when given the chance to talk about. I for one always enjoy hearing people talk about their passions (I just hope that passion aligns with dedication).
        jrflowers 2y ago
        It is always nice to see people engage in the fruitful pedagogical tradition of calling folks internet warriors unprompted >This last part isn't isolated to nuclear technologies and is a common logic failure of many internet warriors.
      - BurningFrog 2y ago
        We're probably all as smart as we need to be :) I thought about getting a little bit deeper into the details, but decided to keep it brief. `godelski`s comment expands on the theme for anyone interested. And all is well!
    - elzbardico 2y ago
      Correct me if I am mistaken, but I always had the impression that the storage requirements for nuclear waste are a lot bigger than what they needed to be, because there's kind of a taboo against widespread processing this waste because this would provide a lot of weapon grade plutonium.
      - 2y ago
  - toomuchtodo 2y ago
    https://www.science.org/content/article/lasers-defuse-nuclear-waste https://www.science.org/content/article/lasers-defuse-nuclea... (“Lasers Defuse Nuclear Waste”)
  - pfdietz 2y ago
    Also, because fission products are weirdly broken into two groups: those with relatively short half lives, and seven ones with very long halflives. The first group is essentially gone after several centuries. The second group has half lives in the hundreds of thousands to millions of years. There is an absence of significant fission product radioactivity in the intermediate range of half lives. There are also actinides with half lives in that range (like, various plutonium isotopes).
    - jojobas 2y ago
      Several centuries is not vastly different from thousands of years, it's still something we have to leave for a distant generation.
      - belorn 2y ago
        Let say you had 1kg of radioactive material that produced 10x the lethal level of radiation. Let say this material has a half life of 6 seconds. Question 1: How many seconds until its below lethal levels. Question 2: How many years will it take until the last atom is gone with a probability of 99%?
      - pfdietz 2y ago
        The importance of the "several centuries" is that it sets an upper limit on how long we can wait before reprocessing or burying (or otherwise permanently disposing of) spent nuclear fuel. After that point, the fuel's gamma activity will have declined so much it is no longer self-protecting from "amateur" reprocessing and diversion of the plutonium. I think it's quite plausible that today's dry casks could last several centuries. So, we have a technology that will last as long as it could be intended to. Arguably it's better for our descendants to do this and let them deal with the waste, not needlessly do something much more expensive. Our descendants will not like that we squandered wealth and left them with larger debts or lower growth either. Always consider what else could be done with resources when you advocate their use.
  - Terr_ 2y ago
    In a similar "sometimes our intuition is wrong" vein, we often learn about types of radiation that are hard to shield against, which makes them automatically scarier than ones "stopped by a sheet of paper." However in some circumstances those types are actually safer to be around, since radiation that can't be stopped is also radiation that isn't interacting and dealing damage. ________________ This relates to the radioactive cookie puzzle, which has many variations, ex: "You have three cookies that emit alpha, beta, and gamma radiation respectively. Choose one cookie to eat, one to put in your pocket, and one to put in a thin lead box." (Partial spoiler) Put the alpha-emitter in your pocket, since it'll be blocked by a layer of fabric and dead skin cells. (Your eyes remain vulnerable, though.) The lead-box would be overkill. Finally, even if it seems easy to manage, the alpha-radiation is not safe: Eating that cookie could kill you, since your important (living) inner cells would be damaged trapping its output. Conversely, eating the gamma-ray emitter is sometimes the best call, because it's not going to be much worse than the other choices, and much of it will leave your body unimpeded.
- babypuncher 2y ago
  This may seem counter-intuitive, but the longer the half-life of a given radioisotope, the less radioactive it actually is. In a given pile of nuclear waste, the scariest stuff is also the first stuff to decay into something stable. It's why waste from power plants only needs to rest in the cooling pool for a few years before it is safe enough to transport to a long term storage facility.
  - mcmoor 2y ago
    I don't feel it's counterintuitive. If we have a leaky cauldron, the bigger the hole, the faster it emptied and vice versa. Although we wouldn't know whether this big stream is because of a big hole or a big jug...
  - pfdietz 2y ago
    As an example: there is a very long lived radioisotope of iodine that occurs in fission products, iodine-129, with a half life of 15 million years. The radioactivity of this isotope is so low that, as I understand it, one could replace every iodine atom in your body with this isotope and you'd still be okay. This would imply it's fine to dispose of this isotope by just dissolving it into the ocean. The ocean's total iodine is about 10^11 tons, so a disposal rate of ~10^4 tons/year would eventually (in ~a half life) make the ocean's iodine mostly I-129 (conservatively, assuming no exchange of iodine is occurring between the ocean and external reservoirs of the element.) This production rate is what would obtain in a totally nuclear powered world at today's primary energy consumption rate.
egorfine 2y ago
> it will inevitably become survivable You're technically right. With Uranium half-life of 4.5b years and current exposure of tens of thousands roentgens per hour, the roadmap to survivability extends well beyond the heat death of the universe, though.
- cowboysauce 2y ago
  Uranium isn't the issue. A long half-life means that it's only mildly radioactive. Prior to being irradiated in a reactor, fuel rods can be manually handled safely. The majority of radiation being emitted currently is coming from fission products like Sr-90 and Cs-137 that have half-lives of decades.

These robots are radiation hardened, and the levels of radiation are steadily decreasing. At some point it will inevitably become survivable.

by jjk166 2y ago

These robots are radiation hardened, and the levels of radiation are steadily decreasing. At some point it will inevitably become survivable.

johnea 2y ago

Exactly! we just need to try again in 10,000 years...

BurningFrog 2y ago
I don't know the numbers, but it's much less! Because if an isotope emits high radiation, it will "burn out" relatively fast. If it lasts thousands of years, it does it by emitting low radiation. And, yes, I know this is a serious comment to sarcasm, but I feel educational today...
- lainga 2y ago
  See the 7-10 rule (of murky and apparently empirical provenance), although this is for fission products of a bomb, not melted fuel https://physics.stackexchange.com/questions/336049/can-the-7-10-rule-of-thumb-for-radiation-be-understood-theoretically https://physics.stackexchange.com/questions/336049/can-the-7...
- godelski 2y ago
  > Because if an isotope emits high radiation, it will "burn out" relatively fast > but I feel educational today... To help people get intuition about this remember that energy is conserved. Radiation can come in multiple forms: alpha (2 protons and 2 neutrons), beta (electron or positron), or gamma (high energy "light"). At each decay even the original atom MUST lose energy, and thus, mass (thanks Einstein!). Alpha is pretty common (how Uranium-238 decays into Thorium-234, in 4.4e9 years, releasing 4.2 MeV of energy[0]). But also note that this is large and that's why it can be stopped pretty easily (unless the MeV is very high). Beta decay is a bit trickier because it can be either a positron or electron, but the process is quite similar. In both alpha and beta decay there's a clear mass being ejected from the atom (and along with it, energy). An example of beta decay is when Thorium-234 decays into Protactinium-234m (m for "metastable") in 24.1 days but with only 0.27MeV (you can tell here thought that this decay releases more energy over time, despite being a lower amount of energy released per decay event). Protactinium-234m then has a VERY short half-life of 1.16 minutes releasing 2.27MeV per event, turning into Protactinium-234, which also has a short half-life of 6.7 hrs, giving off 2.2 MeV of beta- (electron) decay, turning into Uranium-234, which has a long half-life of 2.45e5 years. I think this last example is where people get confused, because we went from Uranium to Uranium, right? But the numbers are important! Uranium-238 to Uranium-234! Those are the number of neutrons in each atom. Uranium-234 is much more stable. (I need to also note that there are some long lived products with high energies, but this is far more complicated than we have time for in this already long comment. We'd have to also discuss biological half-lives if we're going to talk about that. And someone will mention stuff about boars and mushrooms, and not understand) The other confusing part is waste and composition of waste[1]. It's important to note that 90% of waste is "low level", which are things like clothing or tools, and only contain 1% of the total radiation in waste. This stuff is readily disposed of, and the truth here is that were this to all get lost, there would be no real serious danger posed to any{one,thing}. We like to be on the safe side with nuclear, and for good reason (this is again, complicated). But the AMOUNT of waste is __VERY__ little > On average, the waste from a reactor supplying a person’s electricity needs for a year would be about the size of a brick. Only 5 grams of this is high-level waste – about the same weight as a sheet of paper. And, > Unlike any other energy generating industry, the nuclear sector takes full responsibility for all of its waste. So this needs to be remembered when comparing competing energies. This is a common misconception when comparing and people without actual domain expertise here naively look at data and don't understand the assumptions of that data (I'm looking at us, HN...). And it is more complicated than just comparing the full waste generation from solar vs nuclear (as a far too common example. Which these technologies don't compete!) So TLDR: The decay can be simply thought of as "high energy, short lived" while the rest is actually incredibly complicated and exceptional levels of nuance are required for actually making good comparisons. This last part isn't isolated to nuclear technologies and is a common logic failure of many internet warriors. TTLDR: shit is complicated, don't talk about complicated stuff if you're passion doesn't align with your efforts to educate yourself and understand the nuance. [0] https://en.wikipedia.org/wiki/Decay_chain#Uranium_series https://en.wikipedia.org/wiki/Decay_chain#Uranium_series [1] https://world-nuclear.org/nuclear-essentials/what-is-nuclear-waste-and-what-do-we-do-with-it https://world-nuclear.org/nuclear-essentials/what-is-nuclear...
  - jrflowers 2y ago
    I like this comment because it can be summed up as “You are pretty much correct, also I am smarter than you are”
    - godelski 2y ago
      Definitely not. I have no idea how much BurningFrog knows or not. I was just continuing their education. Expanding on their comment, no more. Don't always assume malicious behavior. We're nerds. Sometimes we just get excited to talk about things we've sunken thousands of hours of our lives learning and get excited thinking others might also be excited with this thing we find cool. I hope there are things you get a lot of joy thinking about and when given the chance to talk about. I for one always enjoy hearing people talk about their passions (I just hope that passion aligns with dedication).
      - jrflowers 2y ago
        It is always nice to see people engage in the fruitful pedagogical tradition of calling folks internet warriors unprompted >This last part isn't isolated to nuclear technologies and is a common logic failure of many internet warriors.
    - BurningFrog 2y ago
      We're probably all as smart as we need to be :) I thought about getting a little bit deeper into the details, but decided to keep it brief. `godelski`s comment expands on the theme for anyone interested. And all is well!
  - elzbardico 2y ago
    Correct me if I am mistaken, but I always had the impression that the storage requirements for nuclear waste are a lot bigger than what they needed to be, because there's kind of a taboo against widespread processing this waste because this would provide a lot of weapon grade plutonium.
    - 2y ago
- toomuchtodo 2y ago
  https://www.science.org/content/article/lasers-defuse-nuclear-waste https://www.science.org/content/article/lasers-defuse-nuclea... (“Lasers Defuse Nuclear Waste”)
- pfdietz 2y ago
  Also, because fission products are weirdly broken into two groups: those with relatively short half lives, and seven ones with very long halflives. The first group is essentially gone after several centuries. The second group has half lives in the hundreds of thousands to millions of years. There is an absence of significant fission product radioactivity in the intermediate range of half lives. There are also actinides with half lives in that range (like, various plutonium isotopes).
  - jojobas 2y ago
    Several centuries is not vastly different from thousands of years, it's still something we have to leave for a distant generation.
    - belorn 2y ago
      Let say you had 1kg of radioactive material that produced 10x the lethal level of radiation. Let say this material has a half life of 6 seconds. Question 1: How many seconds until its below lethal levels. Question 2: How many years will it take until the last atom is gone with a probability of 99%?
    - pfdietz 2y ago
      The importance of the "several centuries" is that it sets an upper limit on how long we can wait before reprocessing or burying (or otherwise permanently disposing of) spent nuclear fuel. After that point, the fuel's gamma activity will have declined so much it is no longer self-protecting from "amateur" reprocessing and diversion of the plutonium. I think it's quite plausible that today's dry casks could last several centuries. So, we have a technology that will last as long as it could be intended to. Arguably it's better for our descendants to do this and let them deal with the waste, not needlessly do something much more expensive. Our descendants will not like that we squandered wealth and left them with larger debts or lower growth either. Always consider what else could be done with resources when you advocate their use.
- Terr_ 2y ago
  In a similar "sometimes our intuition is wrong" vein, we often learn about types of radiation that are hard to shield against, which makes them automatically scarier than ones "stopped by a sheet of paper." However in some circumstances those types are actually safer to be around, since radiation that can't be stopped is also radiation that isn't interacting and dealing damage. ________________ This relates to the radioactive cookie puzzle, which has many variations, ex: "You have three cookies that emit alpha, beta, and gamma radiation respectively. Choose one cookie to eat, one to put in your pocket, and one to put in a thin lead box." (Partial spoiler) Put the alpha-emitter in your pocket, since it'll be blocked by a layer of fabric and dead skin cells. (Your eyes remain vulnerable, though.) The lead-box would be overkill. Finally, even if it seems easy to manage, the alpha-radiation is not safe: Eating that cookie could kill you, since your important (living) inner cells would be damaged trapping its output. Conversely, eating the gamma-ray emitter is sometimes the best call, because it's not going to be much worse than the other choices, and much of it will leave your body unimpeded.
babypuncher 2y ago
This may seem counter-intuitive, but the longer the half-life of a given radioisotope, the less radioactive it actually is. In a given pile of nuclear waste, the scariest stuff is also the first stuff to decay into something stable. It's why waste from power plants only needs to rest in the cooling pool for a few years before it is safe enough to transport to a long term storage facility.
- mcmoor 2y ago
  I don't feel it's counterintuitive. If we have a leaky cauldron, the bigger the hole, the faster it emptied and vice versa. Although we wouldn't know whether this big stream is because of a big hole or a big jug...
- pfdietz 2y ago
  As an example: there is a very long lived radioisotope of iodine that occurs in fission products, iodine-129, with a half life of 15 million years. The radioactivity of this isotope is so low that, as I understand it, one could replace every iodine atom in your body with this isotope and you'd still be okay. This would imply it's fine to dispose of this isotope by just dissolving it into the ocean. The ocean's total iodine is about 10^11 tons, so a disposal rate of ~10^4 tons/year would eventually (in ~a half life) make the ocean's iodine mostly I-129 (conservatively, assuming no exchange of iodine is occurring between the ocean and external reservoirs of the element.) This production rate is what would obtain in a totally nuclear powered world at today's primary energy consumption rate.

egorfine 2y ago

> it will inevitably become survivable You're technically right. With Uranium half-life of 4.5b years and current exposure of tens of thousands roentgens per hour, the roadmap to survivability extends well beyond the heat death of the universe, though.

cowboysauce 2y ago
Uranium isn't the issue. A long half-life means that it's only mildly radioactive. Prior to being irradiated in a reactor, fuel rods can be manually handled safely. The majority of radiation being emitted currently is coming from fission products like Sr-90 and Cs-137 that have half-lives of decades.