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passive_fist comments on Global catastrophic risks connected with nuclear weapons and nuclear energy - Less Wrong

1 Post author: turchin 21 December 2015 12:20PM

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Comment author: passive_fist 22 December 2015 12:46:33AM *  3 points [-]

I'd say that the possibility of 'home made nukes' is essentially zero unless fissile isotopes become widely available and cheap, and even if all current controls on nuclear materials and technology were lifted, that would still be far from plausible. The US government pays about $1mil to $10mil worth of plutonium-238 for a single nuclear weapon; this is even though the current industrial process for producing plutonium is highly optimized and efficient (the first nuclear test required $1bn worth of fissile material).

'Home made nuke' is in the same category of plausibility as 'home made fighter jet'.

EDIT: There are some other misconceptions in your document as well. Natural fusion ignition (in materials at densities and pressures you could find anywhere on or in the Earth) is physically impossible to trigger via a nuclear explosion; a thermonuclear weapon only works by imploding some quantity of fuel contained inside the device, and this implosion requires very precise and special conditions to carry out.

'Salted' bombs are largely a myth; ordinary bombs made out of Uranium-238 (most of the current arsenal) produce far more dangerous radioactive isotopes than a hypothetical cobalt bomb. Most nuclear weapons are already 'salted.'

Comment author: turchin 22 December 2015 10:10:45AM *  0 points [-]

It looks like you did not look into details provided inside each of the topic. This proves for me that the idea of interactive pdf was wrong. ((

  1. "Home made nukes" are not about plutonium but about pure fusion weapons. Several ways to create them has been suggested, all listed in the document.

  2. Natural fusion ignition is not about the Earth but about enriched layers of deuterium in Jupiter. The idea is highly speculative, any way.

  3. Salted bomb could create much large contamination as it is specially designed to do so. Most fusion bombs are relatively clean now. Salted bomb may create not only cobalt-60 but other isotopes. Russia in 2015 publish (accidentally) a plan to use 100 MT cobalt bomb torpedos to contaminate US ports.

But the main difference is that cobalt doomsday bomb is very large bomb, probably stationary with yields of gigatons, and most of its energy is used to create dangerous isotopes. In this case it could create enough cobalt-60 to contaminate Earth's surface. It was calculated by Szillard in 1950s and while the exact calculations are secret, I tend to believe him. No known stationary doomsday devices has been created until now ( or we don't know about them.)

Comment author: passive_fist 22 December 2015 06:20:15PM 0 points [-]

I understood your justifications and that's what I was responding to.

  1. There are significant technological barriers to pure fusion weapons and fission implosion triggers would always probably be the cheaper option. Laser-initiated fusion is known to be unworkable; experiments have indicated that at least 10 MJ of laser energy - and probably 2 or 3 times that - is required for reliable fusion ignition; this is far beyond the capabilities of current laser technology to produce in a compact way (the NIF is a huge installation and only produces 1.8 MJ of laser energy). Antimatter-triggered fusion might be possible but we are still far from producing the amount of antimatter required (at least a billion atoms; we've currently only been able to produce about 100 atoms confined for a few minutes).

  2. You mention "Deuterium in lakes and ice has higher concentration" and "Lithium in dry lakes", referring to Earth. As for Jupiter, I wouldn't worry too much about it.

  3. The Russians are known to put out a lot of misleading information; I would take those reports with a grain of salt (ahem). Fact is, most current bombs have a secondary pusher/tamper made of Uranium-238 and this produces nuclear isotopes that are more dangerous and far more plentiful than a cobalt blanket ever would. I fail to see the point of a 'stationary doomsday device' as nuclear ICBMs are far more dangerous (and they already exist).

Comment author: turchin 22 December 2015 08:06:34PM 0 points [-]
  1. The main idea about pure fusion weapons is that we don't know how to make it now, but if we know, it would change a lot in the world. At least 10 different approaches have been studied, and it was shown that small pure fission weapons are possible, but their yield is like 5 tons, so they are not practical now. But if they find the way to combine different approaches it could result in higher yields. For example for laser fusion it was suggested that staged approach may work, where laser fusion of smaller pellet start fusion in higher pellet (http://ufn.ru/ru/articles/1998/11/f/ - article is in russian). It is not proved that pure fusion weapons are possible, but still need to be concerned about them until we will prove that they are impossible.
  2. Lowell Wood in his article (http://journals.aps.org/pra/abstract/10.1103/PhysRevA.20.316, I have pdf) about fusion detonation in planar atmospheres showed minimal conditions for such reaction. It mostly depends of concentration of deuteriem (it should be 20 times more than in oceans, and it is small margin as deutherium and lithium could naturally concentrate in some places) and of the size of primary bomb, which should be as I remember around 300 meters - it is almost impossible to create such device on earth without use of self-replicating nanobots. And on Earth it will be overkill itself. One may be surprised to learn that humanity already sent nuclear device with weapon grade plutonium inside Jupiter, so it is not as remote possibility in the future (I mean drowning of spacecraft Galileo with nuclear batteries in the Jupiter). While Galileo was not able to initiate nuclear detonation of Jupiter, in near future one may create self-replicating nanobots which will be able to build large enough nuke to start detonation of Jupiter. Such explosion would be strong enough to kill all human settlements in Solar system. I also never met understanding (or wise contrarguments) from anyone on this topic and don't like to discuss it as possibility of it is small and very remote.
  3. The main difference between stationary salted bomb (SSB) and ICBM is that SSB is invulnerable to any enemy attack and is able to create much more radioactivity as it is deliberately created for it. It may have yield of 10-100 GT than is many times more than all ICBM combined. Its only useful for nuclear blackmail. The difference is also is in results of its implementation. In case of large scale nuclear war wit ICBM total fatalities are estimated in hundreds millions maximum. Stationary cobalt bomb may result in billion fatalities or total extinction. So it is more dangerous. But we don't know that any was ever build as it is very expensive device, it may cost 10-100 billions dollars.
Comment author: passive_fist 22 December 2015 09:02:49PM *  0 points [-]
  1. Fission weapons with arbitrarily small yields are possible, it's just that you have to sacrifice efficiency. Before the CTBT, tests of < 1 ton yield were routinely carried out as part of hydrodynamic bomb testing. The smallest critical mass for plutonium (assuming an advanced weapon design) seems to be about 2-3 kg, giving a minimum yield of 5-6 kt without losing efficiency (and thus provides a minimum cost bound for a fission weapon). The 10 MJ figure I gave was assuming the smallest possible primary, and a staged design. I think at this point we have a very clear idea of what it would take to make pure fusion weapons work (after all, it is in the highest national security interest to do so) and as I said, all the approaches seem infeasible for now and the foreseeable future.

  2. I'm aware of that study. I wouldn't worry about it; the calculations are extremely optimistic and we don't even know if a segregated deuterium layer exists in Jupiter at all.

  3. I think you are missing the point. The point isn't whether you could build a SSB (although, as I said, I doubt it would be of much use in a nuclear ICBM era). The point is whether 'salting' by cobalt would produce a more dangerous device than you could make with just uranium-238. The answer is: No, in fact a cobalt bomb would be safer than a U-238 device.

Comment author: turchin 22 December 2015 10:55:41PM 0 points [-]
  1. Ups, it was a typo in my last comment "it was shown that small pure fission (read fusion) weapons are possible, but their yield is like 5 tons" . it is in wiki:https://en.wikipedia.org/wiki/Pure_fusion_weapon. No plutonium. I think that we can't exclude possibility that such device may be upgraded (for example, using U-238 blanket) and many other tricks. I have some more links in the map and if one is interested he may follow, but I hope that the best results in pure fusion are kept tightly in secret.
  2. Ok.
  3. Yes, one probably may get more dangerous isotopes using U-238 blanket, if we consider chemistry of isotopes and their ability to accumulate in human body. Strontium, plutonium, Iodine and cesium may result from U-238 fission and all on them could accumulate in human body because of their similarity to calcium or other elements. Internal radiation is also much more dangerous.

But the main idea of salted bomb is not about which type of blanket to use - it is very technical question which require large calculations, and it may be found that some kind of blanket is even more effective in killing all humanity than either cobalt or U-238 (think about C-14, polonium, tritium, combinations etc). The main idea of salted bomb is that it is specially design to produce long term atmospheric contamination and that it is very large and stationary. And it is defence or blackmail weapon, not offensive. By large I mean like 20 000 tons dry weight. And 10-100 gigaton of explosive power. It is much more than all ICBM nukes combined. And most of them do not use U-238 blanket as they try to make them more clean.

By the way one may use ICBM to create something like U-238 salted gigabomb, if he use them to attack existing nuclear power stations. I heard that it was a fear North Korea may attack Japan's nuclear power stations with their nukes. I can't and don't want make exact calculation about it.

Comment author: passive_fist 23 December 2015 12:08:47AM 0 points [-]
  1. I see what you are talking about now. Flux-compression driven fusion is most likely not going to work (which explains why there has been no serious effort to pursue it). It's useful to compare it to the Sandia capacitor-powered Z-machine. To achieve fusion you need (a) a lot of energy, delivered in (b) a short amount of time (preferably nanoseconds as the fuel will tear itself apart at timescales much longer than that), in (c) a very small space. The best EPFCG so far has achieved about 100 MJ and 256 MA, but the killer is the time scale, which is on the excruciatingly slow millisecond level. By contrast, the Sandia machine can deliver about 10 MJ and 27 MA on a nanosecond timescale, and is still far from achieving fusion ignition (currently at least two orders of magnitude away). A planned tripling of energy output via a future upgrade is not expected to produce any fusion ignition either. All of this is evidence against the feasibility of EPFCG fusion. To me, it's damning evidence. A quote in that same page you linked says, "the U.S. Is not known to have and is not developing a pure fusion weapon and no credible design for a pure fusion weapon resulted from the DOE investment".

  2. It's not true that ICBMs do not have U-238 blankets. Virtually all modern warhead designs use a U-238 pusher/tamper and some also use a U-238 hohlraum (some omit this in favor of other metals, but the U-238 tamper is still there). I see what you are saying about a 'blackmail weapon' but I don't see how this is any different from the existing MAD doctrine (via nuclear ICBMs, which are more dangerous and more cost-effective).

Comment author: turchin 23 December 2015 09:17:18AM *  0 points [-]
  1. The only way to really prove that pure fusion weapons are possible would be demonstrate them.... But I will answer more generally. We known that tech progress exist and it tends to make things more effective, cheap and widespread. It do it in many domains. In the middle of 20 century we saw quick progress in nuclear weapons. Could we assume that no any progress is possible in this domain? I think we can't take it for granted. The quote from DOE can't prove that pure weapons are impossible, as I would expect that would say the same if they find the way to create them but want to keep in secret. This claim was made the same year - 1998 - as was published an article which describes 3 ton pure bomb (upgradable to 10 t neutron bomb with U-238 blanket) http://scienceandglobalsecurity.org/archive/sgs07jones.pdf It was almost 20 years ago and we don't know if any progress was made on the topic. Personally I think that pure weapons may be created by some unexpected combination, like cold fusion device compressed by Z-pinch.
  2. MAD doctrine kills only two superpowers, but nuclear blackmail kills all human population of the world as collateral damage. The difference is human extinction.
Comment author: passive_fist 28 December 2015 02:30:17AM 0 points [-]
  1. Strictly speaking, the only major barrier to development of fission weapons (once the possibility of prompt criticality was realized) was enrichment. Even a simple gun-type bomb design suffices if you want to build a fission weapon, but you have to get the nuclear material first, and that's where the bulk of the scientific and technological effort in the Manhattan project was focused. Even today, enrichment is still only the major barrier to aspiring nuclear states/groups. Once it was identified that this was the problem that needed to be solved, the scientists quickly came up with a plan on how to tackle it. But there is no plan or pathway to pure fusion weapons. As far as we know, they could be physically impossible. I'm not discounting the possibility of some incredibly secret pure fusion weapon, but if such a weapon existed it would be exceedingly silly to spend billions of dollars on facilities like NIF or the Z machine - and keep in mind that these projects were funded by and do research for the government agencies responsible for nuclear weapons development. What's the point? (Also, cold fusion does not exist.)

  2. Wrong. A country with a sizeable stockpile of nuclear ICBMs can target and kill anyone it wishes. It's not restricted to just bombing the other superpower.

Comment author: turchin 28 December 2015 10:31:29AM 0 points [-]
  1. This is a map of possible risks, not a map of claims. All it says is that if pure fusion (or other simple nukes) will be created it will make situation with proliferation much more difficult. For example laser enrichment is much simpler than traditional and it was recognised as proliferation risk. We can't say how, but tech progress is making nukes cheaper and simpler and it is a problem. https://en.wikipedia.org/wiki/Separation_of_isotopes_by_laser_excitation
  2. It can kill anyone, but not everyone. The world have around 5 million villages and small towns, and you need at least one bomb for each one to kill. On the peak of cold war the world had less than 100 000 bombs. If you really want to kill everyone, you should try something special like artificial nuclear winter or summer.