7 ms·

The Chernobyl exclusion zone as terrible as it is, is very far from a worst case. It's what you get from a moderately bad meltdown with heroic mitigation effort

by gpm 5y ago

The Chernobyl exclusion zone as terrible as it is, is very far from a worst case. It's what you get from a moderately bad meltdown with heroic mitigation efforts as a follow up. The risks are far greater than that. Holding it up and saying "this isn't bad" is missing that that's the point, this is what happens in a "good" meltdown. An article describing some of it... https://www.thetrumpet.com/14007-three-men-who-saved-millions https://www.thetrumpet.com/14007-three-men-who-saved-million...

DennisP 5y ago
It's also what you get from a reactor with no containment dome, unlike every modern reactor. On top of that, the Chernobyl reactor had a strong positive feedback: as the temperature went up, the reaction sped up. Modern reactors do the opposite.
- Retric 5y ago
  Only up to a point. Modern designs tend to be short term passively safe, but shut off the pumps and radioactive decay alone can be enough to eventually cause a melt down in many modern designs. Which is the core issue, there’s a huge cost trade off for protection vs every possible issue no matter how remote. Spent fuel pools are probably the greatest example of this. They haven’t caused a major issue yet but they’re potentially a much larger risk than the actual reactor.
  - koheripbal 5y ago
    No. Modern reactors use their pumps to keep the reactor going. Shut them off and the reactor shuts itself off. They now all have passive safety systems that do not require power.
  - i_am_proteus 5y ago
    >shut off the pumps and radioactive decay alone can be enough to eventually cause a melt down in many modern designs The newest designs being built worldwide use natural circulation cooling and do not need cooling pumps in emergencies. Eventually the cooling pool needs to be refilled, but it's external to the containment pressure boundary, so you could refill it with a fire truck.
    - Retric 5y ago
      Natural circulation gets heat from a reactor to X, but now your dependent on X. This often seems like a trivial detail, but Fukushima failed 3 days after the earthquake. The issue is you want several things from a passive system at the same time, don’t lose heat in normal operation, quickly lose multiple GW of heat in an emergency and as much as 200+MW of heat for days after a shutdown. The obvious solution is to have a tank of water that boils if the reactor temperature gets to high, but now you need to keep that tank full. Thus many designs result in a reactor that is passively safe for some number of hours and at risk after that. They describe this as a passively safe reactor even if it’s got external dependencies.
      - i_am_proteus 5y ago
        Nope. Decay heat is below a half percent of operating after about a day. So 200 MW decay heat days later would mean a 40GW (thermal) reactor. That's about ten times larger than the largest reactors in existence today. Also, watts measure power, not heat.
        Retric 5y ago
        Watts is joules per second be that electricity, horsepower, or heat. Passive systems can’t assume a successful shutdown.
        mlyle 5y ago
        I can't figure out what you're saying here. You're assuming that the control rods aren't in, days later, for the purpose of calculating heat days after shutdown?
        Retric 5y ago
        I am saying passive safety can’t assume anything else worked.
        5y ago
  - chasil 5y ago
    I know that molten salt reactors have a "salt plug" at the bottom of the tank that will melt if the temperature is too high, dumping the liquid fuel into a boron bath. I think this kind of reactor is safe in a way that no modern reactor is - operators can remove all power and walk away in this shutdown state. This isn't possible with modern reactors, where 6% of the heat that they produce comes from daughter nuclei, and this decay heat requires cooling power for months after a controlled shutdown. I do agree, we have to build these safely, with every conceivable scenario, such that walking away is possible. Converting to thorium fuel would also be far better, as there is only one stable isotope in nature, so no refing is necessary (beyond high-purity smelting), and no centrifuges.
  - godelski 5y ago
    The Soviets were the only ones that built reactors that way. As in, having the ability to blow up. > Spent fuel pools are probably the greatest example of this. They haven’t caused a major issue yet but they’re potentially a much larger risk than the actual reactor. I think you're also over estimating the danger here. We've been operating over 500 reactors for over 70 years. That's some pretty good statistical power.
    - Retric 5y ago
      Edit2: Blowing up isn’t the only risk from a melt down, a major meltdown on a river could contaminate millions of people’s drinking water without any boom. First pools are shared between reactors so there’s probably only around 200 that have ever been built. Also, the risk isn’t simply in year X for pool Y, it’s for every pool and every year. At best we can estimate the risk of a pool over it’s lifetime is probably under 2% and the risk from all pools is also under 2% in any given year. The risk of any pool over the next 50 years, now that we have very little hard data on. At least in terms of real world data ir could be 0.05% or 50% and we just don’t have enough real world data to validate. Edit: You can scroll through this list but it looks like on average there’s around 3 reactors per location. https://en.wikipedia.org/wiki/List_of_commercial_nuclear_reactors https://en.wikipedia.org/wiki/List_of_commercial_nuclear_rea...
      - godelski 5y ago
        > At best we can estimate the risk of a pool over it’s lifetime is probably under 2% and the risk from all pools is also under 2% in any given year How are you getting this number? > The risk of any pool over the next 50 years, now that we have very little hard data on What are you talking about? We have plenty of data. We literally have decades of physical testing and hundreds of millions (if not billions) of dollars worth of simulation testing. What do you think Sierra[0] (#3 super computer in the world) is doing all day? It is a classified machine at a DOE lab. Even a substantial portion of Summit does this same research (it also does a lot of climate research). But come on, 3 of the top 10 super computers are at US DOE labs, and the 3 exascale machines being built are also targeted for DOE labs (Aurora, Frontier, El Capitan (classified)). LLNL and ORNL spend significant resources on nuclear research. [0] https://top500.org/system/179398/ https://top500.org/system/179398/
lasc4r 5y ago
Aren't there fail-safe designs for newer reactors? Whatever tiny risk exists would be worth taking IMO.
- gpm 5y ago
  I'm pretty sure every reactor ever designed was designed to fail safely. Including Chernobyl... I don't trust humans to design and maintain things that actually always fail safely though. Eventually someone is going to do something dumb and cut the wrong corner or, just do something dumb like disable the emergency core cooling system as part of a test of another system (what caused Chernobyl...) In a perfect world fission power could be used safely, the real world isn't perfect, and the pro-nuclear crowds main argument seems to be to go around saying "we're actually perfect now".
  - junon 5y ago
    Chernobyl had an unsafe design from the beginning and the engineers knew it.
    - bumby 5y ago
      It seems to be a combination of poor design and not following operational procedures to manage the poor design. https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/appendices/chernobyl-accident-appendix-1-sequence-of-events.aspx https://world-nuclear.org/information-library/safety-and-sec...
    - merb 5y ago
      fukushima as well, heck even the governement did know that. that does not make it better. in fact that makes it worse.
  - deleted 5y ago
    [deleted]
  - philwelch 5y ago
    > In a perfect world fission power could be used safely, the real world isn't perfect, and the pro-nuclear crowds main argument seems to be to go around saying "we're actually perfect now". This isn’t a criticism of nuclear power; it’s a criticism of industrial civilization and technological progress. You can make the exact same point about coal mining, lithium mining, power grids, hell, even campfires if you wanted to. If I went and dug up horror stories about what happened before we had an electrical code and used those horror stories to argue that we shouldn’t have electricity inside our homes, it would be perfectly reasonable to say, “that’s why we have electrical codes”. And I don’t think it would be a strong counter for me to say, “but the electrical code isn’t perfect”.
agumonkey 5y ago
seems like the debate is still polarizing.. either there were not enough engineering improvement, or bad communication to settle the issue
- gpm 5y ago
  It's not a question of engineering improvement. The comment at the top of this thread said it fairly well: > 4. This it he big one for me: I just don't trust governments or corporations to maintain, inspect, manage and operate nuclear power plants at scale. I'd add "design" and "construct" to that list as well. I have pretty much no doubt that it's theoretically possible to design, construct, maintain and operate a safe reactor, I don't believe for an instant though that the decision making authorities are capable of actually requiring in perpetuity that those things and only those things are done despite the huge financial incentives to cut corners and play the 1-in-a-million catastrophic failure lottery.
  - agumonkey 5y ago
    I quite agree with the dubious government skill levels in general, but considering the task I'd say they made a decent run for a first era so far. 3 big catastrophes (not good not terrible). Question would be, can we raise the safety levels one order up ? Also in a way, we will face that soon because the current fleet will have to be replaced by something one way or another.
  - shawnz 5y ago
    The amount of coal necessary to replace nuclear fuel is about a million times greater. Do you trust those governments to handle 1000000x as much fossil fuel as nuclear? Especially consider the fact that such a large amount of coal has roughly equally as much natural radioactive contaminants as the amount of nuclear fuel that could replace it.
    - gpm 5y ago
      This is a poor argument, you're comparing nuclear to literally the worst alternative you can think of. The alternative to building new nuclear plants is not building new coal plants, or keeping existing coal plants in use for longer. It's to take the same money that you could have spent on new nuclear power plants, and to spend them on new power plants of other types. If it's a fossil fuel form in the modern era, that probably means gas (16% of new power generation in the US), not coal (0% of new capacity I believe, rather quickly being retired/converted to natural gas). More likely it means solar (39%) or wind (31%). (Source for numbers: https://www.eia.gov/todayinenergy/detail.php?id=46416 https://www.eia.gov/todayinenergy/detail.php?id=46416) But yes, I trust our society to handle coal (and other fossil fuels) more than I trust it to handle nuclear plants, because you can't hide the effects of fossil fuels, but you can hide (and deny) the negative effects of a unsafe nuclear plant until it fails catastrophically.
deleted 5y ago
[deleted]
mitch3x3 5y ago
If they would’ve used water as a moderator, built a containment building, and not allowed manual override like every other reactor ever, we wouldn’t be having this conversation. It’s absolutely a worst case scenario.
spfzero 5y ago
Realistically, it was the worst case as modern designs are much safer. What are you imagining would be the very-far worse case and how would that arise? I'd argue Fukushima was a worst-case scenario with a Gen-3 commercial plant.

by gpm 5y ago

DennisP 5y ago

It's also what you get from a reactor with no containment dome, unlike every modern reactor. On top of that, the Chernobyl reactor had a strong positive feedback: as the temperature went up, the reaction sped up. Modern reactors do the opposite.

Retric 5y ago
Only up to a point. Modern designs tend to be short term passively safe, but shut off the pumps and radioactive decay alone can be enough to eventually cause a melt down in many modern designs. Which is the core issue, there’s a huge cost trade off for protection vs every possible issue no matter how remote. Spent fuel pools are probably the greatest example of this. They haven’t caused a major issue yet but they’re potentially a much larger risk than the actual reactor.
- koheripbal 5y ago
  No. Modern reactors use their pumps to keep the reactor going. Shut them off and the reactor shuts itself off. They now all have passive safety systems that do not require power.
- i_am_proteus 5y ago
  >shut off the pumps and radioactive decay alone can be enough to eventually cause a melt down in many modern designs The newest designs being built worldwide use natural circulation cooling and do not need cooling pumps in emergencies. Eventually the cooling pool needs to be refilled, but it's external to the containment pressure boundary, so you could refill it with a fire truck.
  - Retric 5y ago
    Natural circulation gets heat from a reactor to X, but now your dependent on X. This often seems like a trivial detail, but Fukushima failed 3 days after the earthquake. The issue is you want several things from a passive system at the same time, don’t lose heat in normal operation, quickly lose multiple GW of heat in an emergency and as much as 200+MW of heat for days after a shutdown. The obvious solution is to have a tank of water that boils if the reactor temperature gets to high, but now you need to keep that tank full. Thus many designs result in a reactor that is passively safe for some number of hours and at risk after that. They describe this as a passively safe reactor even if it’s got external dependencies.
    - i_am_proteus 5y ago
      Nope. Decay heat is below a half percent of operating after about a day. So 200 MW decay heat days later would mean a 40GW (thermal) reactor. That's about ten times larger than the largest reactors in existence today. Also, watts measure power, not heat.
      - Retric 5y ago
        Watts is joules per second be that electricity, horsepower, or heat. Passive systems can’t assume a successful shutdown.
        mlyle 5y ago
        I can't figure out what you're saying here. You're assuming that the control rods aren't in, days later, for the purpose of calculating heat days after shutdown?
        Retric 5y ago
        I am saying passive safety can’t assume anything else worked.
        5y ago
- chasil 5y ago
  I know that molten salt reactors have a "salt plug" at the bottom of the tank that will melt if the temperature is too high, dumping the liquid fuel into a boron bath. I think this kind of reactor is safe in a way that no modern reactor is - operators can remove all power and walk away in this shutdown state. This isn't possible with modern reactors, where 6% of the heat that they produce comes from daughter nuclei, and this decay heat requires cooling power for months after a controlled shutdown. I do agree, we have to build these safely, with every conceivable scenario, such that walking away is possible. Converting to thorium fuel would also be far better, as there is only one stable isotope in nature, so no refing is necessary (beyond high-purity smelting), and no centrifuges.
- godelski 5y ago
  The Soviets were the only ones that built reactors that way. As in, having the ability to blow up. > Spent fuel pools are probably the greatest example of this. They haven’t caused a major issue yet but they’re potentially a much larger risk than the actual reactor. I think you're also over estimating the danger here. We've been operating over 500 reactors for over 70 years. That's some pretty good statistical power.
  - Retric 5y ago
    Edit2: Blowing up isn’t the only risk from a melt down, a major meltdown on a river could contaminate millions of people’s drinking water without any boom. First pools are shared between reactors so there’s probably only around 200 that have ever been built. Also, the risk isn’t simply in year X for pool Y, it’s for every pool and every year. At best we can estimate the risk of a pool over it’s lifetime is probably under 2% and the risk from all pools is also under 2% in any given year. The risk of any pool over the next 50 years, now that we have very little hard data on. At least in terms of real world data ir could be 0.05% or 50% and we just don’t have enough real world data to validate. Edit: You can scroll through this list but it looks like on average there’s around 3 reactors per location. https://en.wikipedia.org/wiki/List_of_commercial_nuclear_reactors https://en.wikipedia.org/wiki/List_of_commercial_nuclear_rea...
    - godelski 5y ago
      > At best we can estimate the risk of a pool over it’s lifetime is probably under 2% and the risk from all pools is also under 2% in any given year How are you getting this number? > The risk of any pool over the next 50 years, now that we have very little hard data on What are you talking about? We have plenty of data. We literally have decades of physical testing and hundreds of millions (if not billions) of dollars worth of simulation testing. What do you think Sierra[0] (#3 super computer in the world) is doing all day? It is a classified machine at a DOE lab. Even a substantial portion of Summit does this same research (it also does a lot of climate research). But come on, 3 of the top 10 super computers are at US DOE labs, and the 3 exascale machines being built are also targeted for DOE labs (Aurora, Frontier, El Capitan (classified)). LLNL and ORNL spend significant resources on nuclear research. [0] https://top500.org/system/179398/ https://top500.org/system/179398/

lasc4r 5y ago

Aren't there fail-safe designs for newer reactors? Whatever tiny risk exists would be worth taking IMO.

gpm 5y ago
I'm pretty sure every reactor ever designed was designed to fail safely. Including Chernobyl... I don't trust humans to design and maintain things that actually always fail safely though. Eventually someone is going to do something dumb and cut the wrong corner or, just do something dumb like disable the emergency core cooling system as part of a test of another system (what caused Chernobyl...) In a perfect world fission power could be used safely, the real world isn't perfect, and the pro-nuclear crowds main argument seems to be to go around saying "we're actually perfect now".
- junon 5y ago
  Chernobyl had an unsafe design from the beginning and the engineers knew it.
  - bumby 5y ago
    It seems to be a combination of poor design and not following operational procedures to manage the poor design. https://world-nuclear.org/information-library/safety-and-security/safety-of-plants/appendices/chernobyl-accident-appendix-1-sequence-of-events.aspx https://world-nuclear.org/information-library/safety-and-sec...
  - merb 5y ago
    fukushima as well, heck even the governement did know that. that does not make it better. in fact that makes it worse.
- deleted 5y ago
  [deleted]
- philwelch 5y ago
  > In a perfect world fission power could be used safely, the real world isn't perfect, and the pro-nuclear crowds main argument seems to be to go around saying "we're actually perfect now". This isn’t a criticism of nuclear power; it’s a criticism of industrial civilization and technological progress. You can make the exact same point about coal mining, lithium mining, power grids, hell, even campfires if you wanted to. If I went and dug up horror stories about what happened before we had an electrical code and used those horror stories to argue that we shouldn’t have electricity inside our homes, it would be perfectly reasonable to say, “that’s why we have electrical codes”. And I don’t think it would be a strong counter for me to say, “but the electrical code isn’t perfect”.

agumonkey 5y ago

seems like the debate is still polarizing.. either there were not enough engineering improvement, or bad communication to settle the issue

gpm 5y ago
It's not a question of engineering improvement. The comment at the top of this thread said it fairly well: > 4. This it he big one for me: I just don't trust governments or corporations to maintain, inspect, manage and operate nuclear power plants at scale. I'd add "design" and "construct" to that list as well. I have pretty much no doubt that it's theoretically possible to design, construct, maintain and operate a safe reactor, I don't believe for an instant though that the decision making authorities are capable of actually requiring in perpetuity that those things and only those things are done despite the huge financial incentives to cut corners and play the 1-in-a-million catastrophic failure lottery.
- agumonkey 5y ago
  I quite agree with the dubious government skill levels in general, but considering the task I'd say they made a decent run for a first era so far. 3 big catastrophes (not good not terrible). Question would be, can we raise the safety levels one order up ? Also in a way, we will face that soon because the current fleet will have to be replaced by something one way or another.
- shawnz 5y ago
  The amount of coal necessary to replace nuclear fuel is about a million times greater. Do you trust those governments to handle 1000000x as much fossil fuel as nuclear? Especially consider the fact that such a large amount of coal has roughly equally as much natural radioactive contaminants as the amount of nuclear fuel that could replace it.
  - gpm 5y ago
    This is a poor argument, you're comparing nuclear to literally the worst alternative you can think of. The alternative to building new nuclear plants is not building new coal plants, or keeping existing coal plants in use for longer. It's to take the same money that you could have spent on new nuclear power plants, and to spend them on new power plants of other types. If it's a fossil fuel form in the modern era, that probably means gas (16% of new power generation in the US), not coal (0% of new capacity I believe, rather quickly being retired/converted to natural gas). More likely it means solar (39%) or wind (31%). (Source for numbers: https://www.eia.gov/todayinenergy/detail.php?id=46416 https://www.eia.gov/todayinenergy/detail.php?id=46416) But yes, I trust our society to handle coal (and other fossil fuels) more than I trust it to handle nuclear plants, because you can't hide the effects of fossil fuels, but you can hide (and deny) the negative effects of a unsafe nuclear plant until it fails catastrophically.

deleted 5y ago

[deleted]

mitch3x3 5y ago

If they would’ve used water as a moderator, built a containment building, and not allowed manual override like every other reactor ever, we wouldn’t be having this conversation. It’s absolutely a worst case scenario.

spfzero 5y ago

Realistically, it was the worst case as modern designs are much safer. What are you imagining would be the very-far worse case and how would that arise? I'd argue Fukushima was a worst-case scenario with a Gen-3 commercial plant.