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Radiation free blast?

  1. May 17, 2011 #1
    As I understand it there is little difference between a Hydrogen bomb and an atom bomb, but its the Nuclear option which causes the long term affects. So, why did governments move to Nuclear bombs over these other ones?

    Also, can it be that the old ones are better, made to not emit radiation, nothing long lasting anyway?
  2. jcsd
  3. May 17, 2011 #2


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    The original atomic bombs were simply fission devices, either fissioning U-235 or Pu-239. The hydrogen bomb gets most of its energy from fusion, but the fusion system is 'ignited' or detonated by a fissile trigger, basically the guts of an atomic bomb (fissile device).

    Some atomic bombs can be 'boosted' by applying an appropriate neutronic fusion reaction.

    Hydrogen bomb = thermonuclear bomb (usually DT), but not all thermonuclear/fusion systems are hydrogen.

    Nuclear blasts are not radiation free. The basic reactions determine the proportion and spectra of neutrons and photons. A strong neutron flux will activate fallout.
  4. May 18, 2011 #3
    The Starfish Prime (thermonuclear warhead) 1.4 Megaton test, at about 400 km altitude, created a lot of electromagnetic interference (EMP), beautiful auroras, but negligible radioactivation and fallout. See


    Bob S
  5. May 19, 2011 #4


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    According to that wiki article the Starfish Prime test created quite a bit of "orbital fallout" which remained for years and was responsible for destroying many LEO satellites. Imagine if someone were to do that nowadays - any astronauts at the ISS would receive large (possibly fatal) doses, and billions of dollars worth of satellites could be destroyed.
  6. May 19, 2011 #5


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    Starfish Prime created a powerful man-made radiation belt that crippled a lot of satellites. "Fallout" is activated topsoil from an earth-based nuclear blast and so isn't really applicable to a space-based event, but there was plenty of radiation to go around.

  7. May 31, 2011 #6

    Thanks for the info, I've been reading up on what you said. Well, I'm a little more clued up but I didn't know that we could achieve fusion, I thought that is what they were trying to do in the US/UK with lasers to start the process and with helium3 in France. Still, that's not my point.

    What I'm still after is to know if, using something like a kilotonne (A-bomb) could the radiation that is harmful for humans and the environment be stopped, but of course still with the same effect of a blast. I expect an H-bomb would not be able to do this, but I don't know?

    Can an A-bomb, without increasing in size, start to approach megatons, that is unless an h-bomb can be tamed and so no more harmful than exploding TNT itself? I am under the impression that if TNT (in the thousands of tonnes) were to be detonated, you'd achieve the yield but withouth the radiation, but of course this would be hugely impractical.
  8. May 31, 2011 #7
    An A-bomb can't approach megatons without being really big. Too big.

    An H-bomb won't produce less fallout. Mainly because it has an A-bombis side as the trigger as noted. If somehow you could detonate the core of an H-bomb without using an A-bomb or the plutonium booster rod, you'd still create radioactive fallout from the matter around the fusion capsule and the gasses in the atmosphere.
  9. Jun 1, 2011 #8
    Well, no. "Fallout" is actual particulate material that has radioactive debris mixed into it. It gets spread out over an area after a detonation and can be carried long distances on the wind.

    A pure fusion device might neutron activate some of its casing, but that would be minor compared to the fission debris from a regular weapon. Some radioisotopes might be made from atmospheric gases, but that wouldn't be fall-out as such. It'd disperse too far and wide to be hazardous too.
  10. Jun 1, 2011 #9
    Aside from an Atom or Hydrogen bomb I was looking into a Neutron blast, which is the opposite of what I'm researching into. However the design of it is such that the destructive radiation that does the damage to humans is for the purpose of removing them, leaving the area largely intact. So this must mean the radiation is shot lived, where as with nuclear its nocking around for some 700m years.

    The air as I understand it does much of the buffering, to stop the radiation leaking from the blast zone. However the A bomb on Japan hasn't left any long lasting radiation, except in people. So its the H-bomb that is the problem, while the a and n do what they do, its only really instantly and for a short period this occurs for.

    Has anybody got some figures on the longevity of the radiation fall out for these bombs and how far the radiation travels? I understand the N bomb is somewhat safer than the a because the radiation is absorbed, but doesn't linger?

    Clarification would be goo thanks.
  11. Jun 1, 2011 #10
    It is possible to make nuclear weapons that would generate much less fallout than the weapons deployed in militaries today. The reason for the US and Russia deploying these "dirtier" bombs is that for a given weight they were able to make a more destructive "dirty" bomb. A "clean" bomb of the same weight would have had less yield. http://en.wikipedia.org/wiki/Nuclear_weapon_design#Clean_bombs
    Last edited: Jun 1, 2011
  12. Jun 2, 2011 #11


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    A pure fusion warhead would release far less radioactive material, as the main product of fusing tritium and deuterium is simply Helium, which is not radioactive whatsoever. However, each reaction also releases a high energy neutron. These neutrons are uncharged and therefore they are very very hard to stop compared to other forms of radiation.

    A neutron bomb is known as an Enhanced Radiation Weapon: An ERW is a fission-fusion thermonuclear weapon (hydrogen bomb) in which the burst of neutrons generated by a fusion reaction is intentionally allowed to escape the weapon, rather than being absorbed by its other components. The weapon's X-ray mirrors and radiation case, made of uranium or lead in a standard bomb, are instead made of chromium or nickel so that the neutrons can escape.

    NORMALLY these neutrons would be captured by uranium that surrounds the fusion core. These neutrons cause a huge fission chain reaction that release much more energy than a simple fission type weapon.

    MisterX is correct in that we don't use them because for the same size, the yield is much less. But this was back in the cold war where the effects of radiation and fallout were much less known. And arguably more accepted.

    The neutrons released in the explosion penetrate the body and some collide with other molecules and atoms, knocking them out of place, ionizing them, and so forth. When a neutron strikes a DNA section it damages it. This can lead to huge amounts of cell death in high doses, or cancer in lower doses.

    There is definitely leftover radioactive particles from the orignal two a-bombs dropped on japan. Due to cleanup and half life the amount is very low, but it is there. An EWR weapon would cause some radioactive particles to be created by neutron absorbtion and subsequent decay mechanisms, but neutrons themselves decay to protons after about 15 minutes unless inside a nucleus and aren't dangerous on their own.
  13. Jun 3, 2011 #12

    So it seems that at the time they could have researched such a radiation free bomb, they decided not to. Although Fusion as I understand it plays a big part in achieving this. I read a little into fourth generation bombs that are sub WMD, these then if used would surely have to be radiation free? and those are being research right now.
  14. Jun 3, 2011 #13
    I read that with a neutron bomb one of the things that happen with its fallout is that the neutrons react with the air and become absorbed, not lingering and this takes a lot out of the radiation fallouts time in the atmosphere. I understand a neutron bombs fallout its its main advantage but that it doesn't stay for long, 24/week? So combined with a pure Fusion bomb (with I read can be up to 97% and that was decades back) would that not be a clean bomb?

    So if a bomb was purely Fusion (I don't know if we know how to make a 100% Fusion device), it had a lead jacket (not Plutonium - doesn't that cause trouble?) there would be no long lasting radiation like with a nuclear bomb? In fact wasn't that the bomb dropped on Hiroshima? I understand that such a bomb is not big enough and so that's why we use Fission and Neutron versions, but then the physical size of the bomb need just be made bigger? Surely advances have come along to make them smaller, I think I read the first bomb weighed in at 70 tonnes?

    Sure, I understand that, it turns Calcium in bones into something else, but I am looking at it from a global perspective. If a neutron bomb is used on one region, its intended purpose with no doubt be fulfilled, however will the fallout disappear in a few days unlike the nuclear variety that spreads with twinds affects everybody around the world?

    And that's the thing isn't it, the "decay mechanisms" because this all happens in an instant, it's that which can't be modelled so easily. So the Neutron bomb destroys less buildings but removes the inhabitants, while being absorbed (can I say) harmlessly into the air for the most part but for the unknown reactions that occur. How long lasting is that radiation?
  15. Jun 3, 2011 #14


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    There isn't a radiation free bomb. Even the most harmless of fusion fuels still produces dangerous radiation.

    Neutrons themselves would never be a major source of fallout. They either are absorbed by other matter, or decay into a proton, an electron, and a neutrino after about 10-15 minutes of being free.

    The bomb dropped on hiroshima was NOT a fusion bomb at all. It was purely fission, using a non-critical sphere of plutonium compressed by explosives into a critical density to generate the chain reaction. Newer technology and understanding of how everything works has enabled us to reduce the size and mass of the warhead drastically for the same yield, even when not using a fusion phase.

    Assuming a pure fusion warhead, the amount of radioactive fallout would be far less than standard warheads and would disperse as it was spread, falling to very minimal levels very quickly. The time it takes for it to completely decay depends on each isotope produced from the blast.

    It isn't the time taken that matters, it is the specific isotopes of different elements that are created. I can't give you a specific time for the radiation to disappear, as I have no idea what kinds of isotopes are produced and I'm willing to bet it would differ greatly depending on the location of the blast.
  16. Jun 4, 2011 #15

    What I mean by a clean bomb is that presently with the choice of Nuclear the area it's deployed on is not the only area affected. Where as clean, to me, would be the containment of the radiation to that area, with anything swept via the winds dissipating to harmless levels. As with the Fukushima plant, other countries were affected by the radiation carried by the winds, however much of what was spread ended up at safe levels. It would also be the rate at which the radiation in the blast zone disappeared harmlessly also, making it habitable.

    So while a Neutron or Fusion blast would almost always have harmful radiation, at the point of creation, it is the containment of that radiation to the area initially affected that would make it "clean" to others.

    Is it possible to create a pure Fusion bomb with today's understanding? You point out that a reduction in physical size of bombs is a result of our understanding of how these things work; so a Fusion bomb could approach those yields of Fission without the historical sizes required? - that is why they went with Fission over Fusion, for the yield, right?

    Are you saying that blasts can be modelled by computers but the unknown reactions specific to areas cannot? what could be the worst case scenario regarding radiation from a pure Fusion blast? In the case of a Neutron bomb harmful radiation specifically passes through and coats objects, for a short time, while a Fusion bomb is much more geared toward the blast. But with the isotope issue are you saying that is something which would be carried by the winds or coat object in the blast radius?
  17. Jun 6, 2011 #16


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    Sure, a pure fusion warhead would be much cleaner.

    Currently we cannot create a thermonuclear chain reaction without the use of a Fission first stage to power it. While it might be possible to use another source, the immense amount of energy needed over such a small time frame would make any current source much to large compared to using a fission stage.

    You could estimate with fairly accurate results if you knew the content of the soil and buildings and such of the area it would detonate in. I have no idea what the worst case scenario would be, but I would assume that it would be nowhere close to a fission bomb. The issue with the isotopes generated is exactly what I was talking about. The neutrons released would create some radioactive isotopes which would probably be blown around to difference places.
  18. Jun 11, 2011 #17


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    Then you understand INCORRECTLY.

    There is actually a rather substantial difference between H-bombs and A-bombs.

    In fact, the H-bombs use an A-bomb as the "match" to light off the H-bomb part.

    Dr. Gregory Greenman
  19. Jun 12, 2011 #18


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    I think that has already been pretty well answered Morbius.
  20. Jun 12, 2011 #19
    Since this is not a perfect world, bombs will always have some radioactive fall because:

    (1) Not all the fissile material undergoes fission and gets blown away.

    (2) Whatever fissions will produce radioactive fission products.

    (3) There is going to be neutron activation of the environment.

    The third point in interesting because the amount of neutron activated radionuclides depends on the manner the H-Bomb/A-Bomb is detonated air, ground, or underground, and the composition of the environment like soil, rock, and their chemical make up. Moreover, these radionuclide are typically long live because they are close to the island of stability on the table of nuclides.

    This is one reason why Japan recovered quickly from the A-Bombs, because the bombs where detonated in the air. Though they were detonated in the air to maximize the blast.

    Technically, I can only think of an anti-matter bomb that does not produce radioactive materials and only prompt gammas from the annihilation process.

    That being said, I am going to go out on a branch speculate that depending on the matter and anti-matter and their quantum state could you probably produce energetic enough gammas that can knock off nucleons, thus forming radionuclides. My knowledge of quantum mechanics is limited.
  21. Jun 18, 2011 #20
    Anti-proton annihilation produces mostly high energy pions, 1/3 each pi-plus, pi-zero, and pi-minus. The pi zeroes each produce two gammas, the charged pions decay into muons and electron/positrons.
    It is difficult to package antimatter, unless you live in an antigalaxy.

    Bob S
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