5 ms·

Stories like this scare me. With all of the precautions, even things like Fukushima failed and will poison our ocean for millennia. What happens if we have a ru

Stories like this scare me. With all of the precautions, even things like Fukushima failed and will poison our ocean for millennia. What happens if we have a runaway fusion process through some pathway that was unexpected? With all the talk about the LHC possibly producing mini blackholes or magnetic monopoles that could potentially cause protons to decay spontaneously, I don't have enough nuclear physics background to know whether we are inherently safe, or if there is a real risk here.

saagarjha 8y ago
Sustaining fusion is very difficult (we really haven’t solved it yet!). Runaway fusion is only really possible if you can simulate stellar conditions, which requires extreme amounts of energy that must be fed in continiously to maintain temperature and confinement. Plus, the radioactive byproducts are much shorter-lived, and so pose much less of a risk of causing lasting ecological damage. Also, just as a FYI, the LHC has not produced any mini black holes or magnetic monopoles. Anything of the sort would be a major accomplishment, far surpassing the discovery of the Higgs Boson.
frob 8y ago
There's most likely not even a risk to the experiment itself from runaway plasma. Experiments like these use very low-density plasma (mBar) so despite being extremely hot, it's a fairly low mass overall of heated plasma. These experiments regularly lose deconfinement of the plasma within the magnetic fields and it collides into the inner walls of the tokamak and cools back down. This is the main thing these experiments are designed to study: how to keep the plasma stable for longer. Even if there were a larger and hotter mass, we don't have the pressure from gravity here that makes fusion work in the center of stars, so it will just kinda melt things and then cool off, if that.
Quenty 8y ago
Fusion is not a chain reaction. The energy maintained for this is incredible and it can’t run away. Fusion has no toxic or radioactive bioproducts. As a power source fusion is pretty good, which is why it’s such a target for research. See: http://www.fusenet.eu/node/38 http://www.fusenet.eu/node/38
- throwaway_se099 8y ago
  > Fusion has no toxic or radioactive bioproducts. D-T fusion, which is the easiest to achieve and perhaps sustain, directly produces He nuclei (that is, alpha particles) and rather energetic neutrons at 14 MeV. Those neutrons, aside from being a form of ionizing radiation themselves, are bound to transmute some of the surrounding material into radioactive isotopes. So, I don't think that "no toxic or radioactive byproducts" is correct. However, the results are easier to handle than those of fission reactors.
- _nalply 8y ago
  I don't know a lot about fusion, however «no radioactive bioproducts» seems to be off. I just read Wikipedia, and the deuterium-tritium reaction produces neutrons. Radiation seems to be not as bad as for fission reactions, however it is NOT radiation-free.
labster 8y ago
https://news.ycombinator.com/item?id=18004980 https://news.ycombinator.com/item?id=18004980 Calculations have been done in general about runaway fission/fusion already. Hawking showed that mini black holes "evaporate" very rapidly, before anyone would even notice. As for some unexpected pathway, energies like this are reached in stars all the time, and they don't spontaneously explode on a regular basis. If you're talking about a basic science experiment being the Great Filter -- well, maybe. I'm skeptical.
- saagarjha 8y ago
  > As for some unexpected pathway, energies like this are reached in stars all the time, and they don't spontaneously explode on a regular basis. Well, they kind of do… But really, the only reason why stars manage to stay in hydrostatic equilibrium is because of gravity, which we really can’t do on Earth so we settle for fancy magnetic confinement vessels.
jakeogh 8y ago
great vid: https://www.youtube.com/watch?v=KETtEHX3pwo https://www.youtube.com/watch?v=KETtEHX3pwo
kazagistar 8y ago
Uh, worst case it blows up pretty conventionally, lots of heat (but not really, not a lot of actual material is used), and, uh, as far as byproducts... helium? Maybe some lithium or boron o carbon or aomething if things get really wild? Basically it's really really safe as far as byproducts. And yeah, it's a teeny sun, that instantly goes out if you stop feeding it juice, which sounds bad, but it's all the tiny stable particles, not the big slowly decaying scary ones.
- baq 8y ago
  All that neutron activated equipment needs to be disposed of, but I guess that’s easier to do than cleaning up a fission reactor.
  - Cthulhu_ 8y ago
    I read in another thread that the radiation in that dissipates in about 30 years, vastly preferable to the tens of thousands of years of nuclear fission waste. I don't know how strong the radiation is either, whether it's more or less dangerous than fission waste.
    - quotemstr 8y ago
      The way radioactivity works, the faster a substance decays, the more dangerous it is. Something being slightly radioactive for ten thousand years is much better than some searing-hot exotic isotope sitting around for 40.
      - frob 8y ago
        Not really. The big issue is with long-term deterrence, not short-term. It is fairly easy to isolate something for 30/50/100/200 years. It is much harder to isolate something from future humanity with a high level of certainty for 200,000 years. Even things with low levels of radioactivity will kill you if ingested and do a lot of harm if kept near. The problem of communicating this to future humans is a big one. How do you keep future humans who may not have the level of technology we have from deciding that the magic, glowing, heating stone is a source of healing and prosperity instead of something to be avoided?
kungtotte 8y ago
The earthquake was the most powerful to ever hit Japan and the fourth most powerful in the world since modern record keeping began, and the investigation into the disaster showed that the safety precautions weren't adequate in the first place. You can't dismiss the technology based on that incident. Just like we don't ban cars because a lot of people don't operate them properly.
- oldgradstudent 8y ago
  When I was in high school we visited a small 5MW nuclear reactor. It was a few years after Chernobyl and we got a very long lecture about how this was all the fault of the terrible Soviet design and that it could never happen in a western-designed nuclear reactor. As far as I remember from the news at the time, the tsunami was terrible, but not unprecedented. If this obvious risk was ignored, what other risks are being ignored elsewhere?
  - kungtotte 8y ago
    A Chernobyl accident can't happen in a western reactor, and it wasn't what happened in Fukushima either, so the lecturers weren't wrong. I don't know the facts of the tsunami whether it was unprecedented or not, but considering the magnitude of the quake I'm guessing it was one of the largest tsunamis to ever hit Japan. This is speculation on my part. They didn't ignore the risk of tsunamis, they had precautions against them but they weren't up to par. It was a series of malfunctioning safeties that caused the accident. The backup power generators conked out, and the backup to the backup was washed away by the floods. And the floods only managed to get that far because the protective walls weren't enough. "Build better walls" seems like a trivial problem to solve, don't you think? International regulatory bodies could also be more proactive in finding these flaws prior to accidents. It's not a hard problem to solve in the long run. It'll be easier and quicker than finding a viable non-nuclear energy option anyway.
    - oldgradstudent 8y ago
      > A Chernobyl accident can't happen in a western reactor, and it wasn't what happened in Fukushima either, so the lecturers weren't wrong. He was referring to the core meltdown, not the very specific fault mechanism. I should have made it clear. Otherwise, it would be an uninteresting technicality. The entire Fukushima incident makes me suspect it's a result of defining an exact fault model and then optimizing to the model. This way, if the fault slightly exceeds the model, the result is not graceful degradation, but catastrophic failure. Can we put the generators below sea level? sure, the sea wall is high enough, no need to worry about that at all. > "Build better walls" seems like a trivial problem to solve, don't you think? Yes, but is it a robust solution?
red75prime 8y ago
> poison our ocean for millennia On global scale it negligibly increased ever-present background radiation. It's not a good thing, but far from poisoning.
- Cthulhu_ 8y ago
  Wasn't said ever-present background radiation only a thing after the nuclear bomb tests? I read a while ago that steel from old ships that sunk deep is highly valuable because it's not irradiated yet.
  - red75prime 8y ago
    It is low-backgroud steel([0]), not no-backbround steel. Potassium-40, for example, is a naturally occurring radioisotope. See Banana equivalent dose ([1]). [0]: https://en.wikipedia.org/wiki/Low-background_steel https://en.wikipedia.org/wiki/Low-background_steel [1]: https://en.wikipedia.org/wiki/Banana_equivalent_dose https://en.wikipedia.org/wiki/Banana_equivalent_dose
    - consp 8y ago
      To add: C-14, Al-26, Cl-36, Ca-41, Ca-48, V-50 and more in trace quantities can be present. Try pointing a Geiger counter at a brick or ever better plaster wall and be surprised about the amount of radiation you get during the day.
  - lolc 8y ago
    To a first approximation all matter on earth radiates because all matter is present with some isotopes that will eventually decay. Don't forget that we're sitting on top of a huge ball of molten metal kept hot by ongoing nuclear decay. That process produces all kinds of isotopes that eventually make their way to the surface. The bomb tests did increase background radiation for us; irresponsibly so in my opinion. But so does burning coal. We have been lifting the level of background radiation over the natural level for centuries by now. I don't see how sunk steel would be any more valuable than steel from freshly mined ore. But I like to be surprised about these things :-)
zaarn 8y ago
Fusion processes cannot go "runaway" (unless you manage to recreate an entire star in the lab by accident, which requires a lot more mass than we have). If a fusion reactor is breached, the plasma will likely dump it's thermal energy into the air (likely this will cause a minor detonation, it's strength depends on the energy in the reactor and the amount of fuel). Additionally it'll leak some short lived isotopes and maybe create a few long live ones. All in all, a detonated fusion reactor is likely save to walk in the same year it exploded, if not significantly earlier.
SmellyGeekBoy 8y ago
> I don't have enough nuclear physics background to know whether we are inherently safe, or if there is a real risk here. Then don't spread FUD?
dwaltrip 8y ago
Low quality news aside, the LHC never had a risk of producing micro-blackholes that could cause any damage. Very tiny blackholes evaporate instantly, before they have time to do anything. The LHC would detected this, which has not happened.

saagarjha 8y ago

Sustaining fusion is very difficult (we really haven’t solved it yet!). Runaway fusion is only really possible if you can simulate stellar conditions, which requires extreme amounts of energy that must be fed in continiously to maintain temperature and confinement. Plus, the radioactive byproducts are much shorter-lived, and so pose much less of a risk of causing lasting ecological damage. Also, just as a FYI, the LHC has not produced any mini black holes or magnetic monopoles. Anything of the sort would be a major accomplishment, far surpassing the discovery of the Higgs Boson.

frob 8y ago

There's most likely not even a risk to the experiment itself from runaway plasma. Experiments like these use very low-density plasma (mBar) so despite being extremely hot, it's a fairly low mass overall of heated plasma. These experiments regularly lose deconfinement of the plasma within the magnetic fields and it collides into the inner walls of the tokamak and cools back down. This is the main thing these experiments are designed to study: how to keep the plasma stable for longer. Even if there were a larger and hotter mass, we don't have the pressure from gravity here that makes fusion work in the center of stars, so it will just kinda melt things and then cool off, if that.

Quenty 8y ago

Fusion is not a chain reaction. The energy maintained for this is incredible and it can’t run away. Fusion has no toxic or radioactive bioproducts. As a power source fusion is pretty good, which is why it’s such a target for research. See: http://www.fusenet.eu/node/38 http://www.fusenet.eu/node/38

throwaway_se099 8y ago
> Fusion has no toxic or radioactive bioproducts. D-T fusion, which is the easiest to achieve and perhaps sustain, directly produces He nuclei (that is, alpha particles) and rather energetic neutrons at 14 MeV. Those neutrons, aside from being a form of ionizing radiation themselves, are bound to transmute some of the surrounding material into radioactive isotopes. So, I don't think that "no toxic or radioactive byproducts" is correct. However, the results are easier to handle than those of fission reactors.
_nalply 8y ago
I don't know a lot about fusion, however «no radioactive bioproducts» seems to be off. I just read Wikipedia, and the deuterium-tritium reaction produces neutrons. Radiation seems to be not as bad as for fission reactions, however it is NOT radiation-free.

labster 8y ago

https://news.ycombinator.com/item?id=18004980 https://news.ycombinator.com/item?id=18004980 Calculations have been done in general about runaway fission/fusion already. Hawking showed that mini black holes "evaporate" very rapidly, before anyone would even notice. As for some unexpected pathway, energies like this are reached in stars all the time, and they don't spontaneously explode on a regular basis. If you're talking about a basic science experiment being the Great Filter -- well, maybe. I'm skeptical.

saagarjha 8y ago
> As for some unexpected pathway, energies like this are reached in stars all the time, and they don't spontaneously explode on a regular basis. Well, they kind of do… But really, the only reason why stars manage to stay in hydrostatic equilibrium is because of gravity, which we really can’t do on Earth so we settle for fancy magnetic confinement vessels.

jakeogh 8y ago

great vid: https://www.youtube.com/watch?v=KETtEHX3pwo https://www.youtube.com/watch?v=KETtEHX3pwo

kazagistar 8y ago

Uh, worst case it blows up pretty conventionally, lots of heat (but not really, not a lot of actual material is used), and, uh, as far as byproducts... helium? Maybe some lithium or boron o carbon or aomething if things get really wild? Basically it's really really safe as far as byproducts. And yeah, it's a teeny sun, that instantly goes out if you stop feeding it juice, which sounds bad, but it's all the tiny stable particles, not the big slowly decaying scary ones.

baq 8y ago
All that neutron activated equipment needs to be disposed of, but I guess that’s easier to do than cleaning up a fission reactor.
- Cthulhu_ 8y ago
  I read in another thread that the radiation in that dissipates in about 30 years, vastly preferable to the tens of thousands of years of nuclear fission waste. I don't know how strong the radiation is either, whether it's more or less dangerous than fission waste.
  - quotemstr 8y ago
    The way radioactivity works, the faster a substance decays, the more dangerous it is. Something being slightly radioactive for ten thousand years is much better than some searing-hot exotic isotope sitting around for 40.
    - frob 8y ago
      Not really. The big issue is with long-term deterrence, not short-term. It is fairly easy to isolate something for 30/50/100/200 years. It is much harder to isolate something from future humanity with a high level of certainty for 200,000 years. Even things with low levels of radioactivity will kill you if ingested and do a lot of harm if kept near. The problem of communicating this to future humans is a big one. How do you keep future humans who may not have the level of technology we have from deciding that the magic, glowing, heating stone is a source of healing and prosperity instead of something to be avoided?

kungtotte 8y ago

The earthquake was the most powerful to ever hit Japan and the fourth most powerful in the world since modern record keeping began, and the investigation into the disaster showed that the safety precautions weren't adequate in the first place. You can't dismiss the technology based on that incident. Just like we don't ban cars because a lot of people don't operate them properly.

oldgradstudent 8y ago
When I was in high school we visited a small 5MW nuclear reactor. It was a few years after Chernobyl and we got a very long lecture about how this was all the fault of the terrible Soviet design and that it could never happen in a western-designed nuclear reactor. As far as I remember from the news at the time, the tsunami was terrible, but not unprecedented. If this obvious risk was ignored, what other risks are being ignored elsewhere?
- kungtotte 8y ago
  A Chernobyl accident can't happen in a western reactor, and it wasn't what happened in Fukushima either, so the lecturers weren't wrong. I don't know the facts of the tsunami whether it was unprecedented or not, but considering the magnitude of the quake I'm guessing it was one of the largest tsunamis to ever hit Japan. This is speculation on my part. They didn't ignore the risk of tsunamis, they had precautions against them but they weren't up to par. It was a series of malfunctioning safeties that caused the accident. The backup power generators conked out, and the backup to the backup was washed away by the floods. And the floods only managed to get that far because the protective walls weren't enough. "Build better walls" seems like a trivial problem to solve, don't you think? International regulatory bodies could also be more proactive in finding these flaws prior to accidents. It's not a hard problem to solve in the long run. It'll be easier and quicker than finding a viable non-nuclear energy option anyway.
  - oldgradstudent 8y ago
    > A Chernobyl accident can't happen in a western reactor, and it wasn't what happened in Fukushima either, so the lecturers weren't wrong. He was referring to the core meltdown, not the very specific fault mechanism. I should have made it clear. Otherwise, it would be an uninteresting technicality. The entire Fukushima incident makes me suspect it's a result of defining an exact fault model and then optimizing to the model. This way, if the fault slightly exceeds the model, the result is not graceful degradation, but catastrophic failure. Can we put the generators below sea level? sure, the sea wall is high enough, no need to worry about that at all. > "Build better walls" seems like a trivial problem to solve, don't you think? Yes, but is it a robust solution?

red75prime 8y ago

> poison our ocean for millennia On global scale it negligibly increased ever-present background radiation. It's not a good thing, but far from poisoning.

Cthulhu_ 8y ago
Wasn't said ever-present background radiation only a thing after the nuclear bomb tests? I read a while ago that steel from old ships that sunk deep is highly valuable because it's not irradiated yet.
- red75prime 8y ago
  It is low-backgroud steel([0]), not no-backbround steel. Potassium-40, for example, is a naturally occurring radioisotope. See Banana equivalent dose ([1]). [0]: https://en.wikipedia.org/wiki/Low-background_steel https://en.wikipedia.org/wiki/Low-background_steel [1]: https://en.wikipedia.org/wiki/Banana_equivalent_dose https://en.wikipedia.org/wiki/Banana_equivalent_dose
  - consp 8y ago
    To add: C-14, Al-26, Cl-36, Ca-41, Ca-48, V-50 and more in trace quantities can be present. Try pointing a Geiger counter at a brick or ever better plaster wall and be surprised about the amount of radiation you get during the day.
- lolc 8y ago
  To a first approximation all matter on earth radiates because all matter is present with some isotopes that will eventually decay. Don't forget that we're sitting on top of a huge ball of molten metal kept hot by ongoing nuclear decay. That process produces all kinds of isotopes that eventually make their way to the surface. The bomb tests did increase background radiation for us; irresponsibly so in my opinion. But so does burning coal. We have been lifting the level of background radiation over the natural level for centuries by now. I don't see how sunk steel would be any more valuable than steel from freshly mined ore. But I like to be surprised about these things :-)

zaarn 8y ago

Fusion processes cannot go "runaway" (unless you manage to recreate an entire star in the lab by accident, which requires a lot more mass than we have). If a fusion reactor is breached, the plasma will likely dump it's thermal energy into the air (likely this will cause a minor detonation, it's strength depends on the energy in the reactor and the amount of fuel). Additionally it'll leak some short lived isotopes and maybe create a few long live ones. All in all, a detonated fusion reactor is likely save to walk in the same year it exploded, if not significantly earlier.

SmellyGeekBoy 8y ago

> I don't have enough nuclear physics background to know whether we are inherently safe, or if there is a real risk here. Then don't spread FUD?

dwaltrip 8y ago

Low quality news aside, the LHC never had a risk of producing micro-blackholes that could cause any damage. Very tiny blackholes evaporate instantly, before they have time to do anything. The LHC would detected this, which has not happened.