# Deaths from a 400 kiloton nuclear explosion **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2022, 8:08pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168 "2022-11-01T20:08:56Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [November 2, 2022, 7:04pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/21 "2022-11-02T19:04:33Z")
> [@Just\_Asking\_Questions](#): > > Except… there were survivors in Hiroshima that were within 1000 feet of ground zero. And they lived for decades. True, but the proposed bomb is 400 kiloton rather than the 10-20 kiloton used in Hiroshima. Never say never, but that’s a big difference. With a 400 kiloton detonating ~2000ft up, rather than the 10-20 kiloton for Hiroshima, within 1000 feet they are almost certainly vaporized instead, much less surviving for any length of time intact or avoiding third degree burns or radiation exposure. ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [November 2, 2022, 7:08pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/22 "2022-11-02T19:08:45Z")
> [@Just\_Asking\_Questions](#): > > Except… there were survivors in Hiroshima that were within 1000 feet of ground zero. And they lived for decades. “1000 feet” from ground zero is NOT ground zero. Especially with what would now be considered a low-yield nuke in an airburst (20 kiloton at most, and likely more in the 10-15 kt range). I’ll also note that ALL of those survivors were, in some manner, shielded from the blast and thermal effects, even if imperfectly. Obviously, the more shielding you have the more likely you are to survive. 400 kiloton bomb would be a different matter. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [November 2, 2022, 7:33pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/23 "2022-11-02T19:33:23Z")
> [@Dahu](#): > > > [@](#): > > > > - Entire population dead within 2-14 days from radiation poisoning > > My question is about the last one, it seems like a heck of a lot (the NW of England is heavily populated). Could it be accurate? No, that’s an obvious fabrication and nowhere near accurate for any scenario. According to Nukemap, a 400kt detonation at altitude of 2km would cause a 500rem radiation dose for about a 1km radius. That means in about a month, 15% of those people would be dead, but most people that close to the hypocenter will be (almost) instantly dead anyway blast and thermal effects. I _think_ they got the 36 mile figure from the maximum width of the downwind fallout cone for a surface burst. That’s entirely distinct from the blast radius, and survivability depends on all sorts of exposure factors like shelter, clothing, decay, etc. Maybe if everyone downwind stayed outdoors naked for an entire month, and the fallout products never decayed, all of them would _at least_ catch a big enough dose to make them sick. But none of those assumptions are especially likely. Not to downplay it, it would certainly be a calamity, but the details presented aren’t correct. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 2, 2022, 8:57pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/24 "2022-11-02T20:57:39Z")
> [@LSLGuy](#): > > And don’t have good blast resistance, so are likely to cave in with only slight blast overpressures. Not relevant. The radiation will arrive before the pressure wave. But it is relevant that the concrete isn’t solid, because the air gap in the middle of a concrete block won’t do diddly against gammas. Oh, and depending on the kind of bomb, there might also be a significant amount of neutron radiation. Your best shielding from that is going to be a lot of water between you and the blast, or maybe hydrocarbon fuels (though the fuel might not look like such a great idea when the blast wave hits and the fires spread). ---
**Author:** ![Loggins](https://avatars.discourse-cdn.com/v4/letter/l/74df32/32.png) [@Loggins](https://boards.straightdope.com/u/Loggins)\ **Post date:** [November 3, 2022, 12:39am UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/25 "2022-11-03T00:39:36Z")
Someone over here mentioned that people exposed to radiation would die within a short time (dont remember how close proximity, but pretty close). I thought that radiation caused cancer and long time sickness, can it kill in hours or other short times? ---
**Author:** ![Dissonance](https://avatars.discourse-cdn.com/v4/letter/d/85f322/32.png) [@Dissonance](https://boards.straightdope.com/u/Dissonance)\ **Post date:** [November 3, 2022, 2:04am UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/26 "2022-11-03T02:04:07Z")
There’s two ways to die from acute radiation syndrome, depending upon the severity of the immediate dose, there’s a table on dosage levels [here](https://en.wikipedia.org/wiki/Acute_radiation_syndrome#Dose_effects). If whole body dosage is greater than 8Gy, death will occur within 2-14 days up to 30Gy or more, at which levels death will occur within 48 hours, with no latency period in either case. Lower doses will cause immediate symptoms (nausea, vomiting, diarrhea, headache, fever, and cognitive impairment) that will subside within 48 hours, at which point the latency period sets in for up to 4 weeks, after which death will occur within 1-2 weeks. That’s just the effects from ARS, long term increased rates of cancer and leukemia happen from lower immediate doses. ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [November 3, 2022, 2:04am UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/27 "2022-11-03T02:04:10Z")
Depends on exposure level and other factors. > **[Acute radiation syndrome](https://en.wikipedia.org/wiki/Acute_radiation_syndrome)** > > Acute radiation syndrome (ARS), also known as radiation sickness or radiation poisoning, is a collection of health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. Symptoms can start within an hour of exposure, and can last for several months. Early symptoms are usually nausea, vomiting and loss of appetite. In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, ARS involves a... (whoops, got ninja’d on the link) ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [November 3, 2022, 2:52am UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/28 "2022-11-03T02:52:12Z")
As a good overview you can consider acute radiation sickness and long term cancers as the two ends of a spectrum of damage to DNA. The difference is that large amounts of damage leads to cell death whilst small amounts of damage where the cell survives can mean amongst the damaged cells are some with mutations that leave them more prone to lead to cancers. Cells that receive a significant amount of damage initiate programmed cell death. In normal circumstances this might be regarded as a good thing as it removes potential cancer cells. But en-mass not so good. Damaging radiation here is usually termed _ionising_ radiation. Gamma rays and neutrons are ionising. They are so termed because they ionise atoms they hit. Sometimes many atoms. These ionised compounds aka radicals, when created in cells, are quite destructive and damage or degrade what they hit next. Cells that take a big hit are those that are dividing, as during this process DNA strands are unwound and relatively unprotected from damage. Cell lines that are ordinarily fast replenishing are most vulnerable. So gut lining, blood production, skin take a disproportionate hit. Enough damage and your body ceases to be able to create any more, and you die within weeks. The central nervous system is however different. It degrades quickly due to oxidative stress brought on by the damaging radicals. Neurons and nerves operate with a delicate chemistry across the cell walls, and damage to the cell walls or operation of the machinery that maintains the potential across the walls leads to degradation of CNS function. This will also kill you. ---
**Author:** ![Loggins](https://avatars.discourse-cdn.com/v4/letter/l/74df32/32.png) [@Loggins](https://boards.straightdope.com/u/Loggins)\ **Post date:** [November 3, 2022, 6:13am UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/29 "2022-11-03T06:13:12Z")
Scarier than i knew ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [November 3, 2022, 4:36pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/30 "2022-11-03T16:36:24Z")
One thing I read said that ionizing radiation is much like cooking - both break down the complex molecules that allow life to proceed, and then break things down even more to change organic matter. The difference is, if you burn yourself, it’s generally localized to near the heat source, whereas radiation does the same thing but neatly distributed all through the human body. ---
**Author:** ![Cwturner](https://avatars.discourse-cdn.com/v4/letter/c/f0a364/32.png) [@Cwturner](https://boards.straightdope.com/u/Cwturner)\ **Post date:** [November 3, 2022, 5:49pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/31 "2022-11-03T17:49:56Z")
I saw Neil deGrasse Tyson on Bill Maher’s show a week or 2 ago where he said a modern hydrogen bomb gives off almost no radiation compared to the atomic/Hiroshima bomb. It was off topic and they really didnt discuss it but I was surprised to hear that. Maybe I misunderstood? CW ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [November 3, 2022, 6:05pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/32 "2022-11-03T18:05:04Z")
Yeah, it’s true. It’s not zero radiation but a modern H-bomb (vs something like the Hiroshima bomb or like the early ones North Korea tested) can significantly reduce how much radioactive fallout there will be. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [November 3, 2022, 6:25pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/33 "2022-11-03T18:25:20Z")
> [@Cwturner](#): > > I saw Neil deGrasse Tyson on Bill Maher’s show a week or 2 ago where he said a modern hydrogen bomb gives off almost no radiation compared to the atomic/Hiroshima bomb. > [@Great\_Antibob](#): > > Yeah, it’s true. No, it’s completely untrue. As is usually the case when Tyson gets out of his lane, he’s spouting off with no clue what he’s talking about. Some reasons he _might_ be confused: - All nuclear bombs involve some amount of fusion. The more energy derived from fusion, the cleaner it can be _relative to the yield_. But all modern nuclear bombs involve at least one fission stage that will, in absolutely terms, produce a similar amount of contamination to the Hiroshima and Nagasaki bombs. - A 100% fusion bomb would theoretically be very clean, no dirty isotopes at all. But no such bomb has ever been built. The max I think is 93% and these were determined to be of less military value than the dirtier versions. - Modern bombs are more likely to be airbursts at significant altitude, and the fallout from these would tend to disperse over a wider area, making them less harmful. But whatever case we’re talking about, even a 100% pure fusion device produces a lot of radiation, just not a lot of fallout containing short-lived radioactive isotopes. Tyson _really_ needs to learn to stay in his lane. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [November 3, 2022, 6:59pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/34 "2022-11-03T18:59:48Z")
FWIW, Nukemap says 260,400 killed, and 659,390 injured for a 400kt warhead airburst directly over the Albert Memorial in Albert Square at 2300 m (to maximize the 5 psi radius). At that altitude, prompt radiation effects are negligible in terms of fatalities, in that the 500 rem radius is 2230 meters. A surface burst is considerably less lethal, with only 166,120 killed and 283,980 wounded, but the fallout distance is considerable, reaching as far as Liverpool or Sheffield with potentially lethal fallout, and Birmingham with maybe not lethal, but still high radiation fallout. > [@HMS\_Irruncible](#): > > No, it’s completely untrue. As is usually the case when Tyson gets out of his lane, he’s spouting off with no clue what he’s talking about. > > Some reasons he _might_ be confused: > > - All nuclear bombs involve some amount of fusion. The more energy derived from fusion, the cleaner it can be _relative to the yield_. But all modern nuclear bombs involve at least one fission stage that will, in absolutely terms, produce a similar amount of contamination to the Hiroshima and Nagasaki bombs. > - A 100% fusion bomb would theoretically be very clean, but no such bomb has ever been built. The max I think is 93% and these were determined to be of less military valuable than the dirtier versions. > - Modern bombs are more likely to be airbursts at significant altitude, and the fallout from these would tend to disperse over a wider area, making them less harmful. He’s not as wrong as you are describing. Let’s take a B61 bomb, the primary US gravity bomb. It’s got what’s called variable yield (“dial-a-yield”) fusing, meaning that it can be set to a series of yields anywhere between 0.3 kilotons and, depending on the model as high as 340 kilotons. Let’s take the B61 Mod 12, which is the most recent model, having been devised in 2019. It’s got four possible yields- 0.3, 1.5, 10 or 50 kt. I would imagine that they correspond to the bare, unboosted primary for 0.3, and the 1.5 and 10 are probably some combination of tritium boosting and external neutron initiation for the primary, and the 50 is almost certainly the whole enchilada including the fusion secondary. So where Tyson’s going is that a 0.3 kiloton unboosted primary isn’t going to create as much fallout as say… the 15 kiloton unboosted fission bomb used on Hiroshima. There’s just less fissile material to create fallout, regardless of whether it’s boosted or not, or even with the full fission secondary firing. So it’s extremely likely that the 50 kt full enchilada detonation of a B61 Mod 12 is inherently less fallout producing than the 15 kt Hiroshima bomb. Where he’s wrong or glossing over something, is that any 50 kt detonation is going to generate more prompt radiation than a 15 kt one, even if one’s fission, and one’s fusion. But here’s where it gets interesting. For a 50 kt detonation, the prompt radiation radius is not really pertinent. If it’s a surface burst, it’s basically contiguous with the 5 psi contour, and if it’s an airburst, it’ll likely be too high to be lethal to people on the ground. ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [November 3, 2022, 7:36pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/35 "2022-11-03T19:36:40Z")
> [@HMS\_Irruncible](#): > > Modern bombs are more likely to be airbursts at significant altitude, and the fallout from these would tend to disperse over a wider area, making them less harmful. Airbursts also tend to produce less fallout than surface bursts. Not zero, just less than they would if they detonated on the ground. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [November 4, 2022, 1:46pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/36 "2022-11-04T13:46:20Z")
> [@bump](#): > > So where Tyson’s going is that a 0.3 kiloton unboosted primary isn’t going to create as much fallout as say… the 15 kiloton unboosted fission bomb used on Hiroshima. It’s uncontroversially correct to say that a 0.3 kiloton unboosted primary will produce less prompt radiation and fission products than any other type of bomb. But Tyson was speaking broadly and categorically, and that’s only one very narrow case. > [@](#): > > There’s just less fissile material to create fallout, regardless of whether it’s boosted or not, or even with the full fission secondary firing. So it’s extremely likely that the 50 kt full enchilada detonation of a B61 Mod 12 is inherently less fallout producing than the 15 kt Hiroshima bomb. No, this is wrong. In most nuclear bombs, the fusion reaction only makes a minority contribution to the yield. The main role of the fusion stage is to generate neutrons that cause fission in the tamper and the jacket, and this is where the majority of the yield comes from. So even if you use a very optimistic figure of 50% contribution of the fusion yield, in your above scenario that still implies enough fission for a 25kt yield, which would create _more_ fallout than the Hiroshima bomb. Don’t overthink what Tyson actually meant. He is of course an expert in astrophysics, but outside of that, he frequently spouts bullshit on topics where he has no expertise and does none of the homework. He just repeated something he overheard or skimmed for 5 seconds, and assumes it’s correct because nobody ever gives him any pushback. > [@](#): > > Airbursts also tend to produce less fallout than surface bursts. Not zero, just less than they would if they detonated on the ground. This is correct. They suck up less material that can be fusion-activated, and the higher the altitude, the longer it takes for the products to settle, so they have more time to decay into something safer (as well as being dispersed over a wider area). ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [November 4, 2022, 3:01pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/37 "2022-11-04T15:01:45Z")
> [@HMS\_Irruncible](#): > > This is correct. They suck up less material that can be fusion-activated, Missed edit window, of course I meant to say “neutron activated” here. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [November 4, 2022, 3:32pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/38 "2022-11-04T15:32:06Z")
> [@HMS\_Irruncible](#): > > No, this is wrong. In most nuclear bombs, the fusion reaction only makes a minority contribution to the yield. The main role of the fusion stage is to generate neutrons that cause fission in the tamper and the jacket, and this is where the majority of the yield comes from. So even if you use a very optimistic figure > of 50% contribution of the fusion yield, in your above scenario that still implies enough fission for a 25kt yield, which would create _more_ fallout than the Hiroshima bomb. I’m not so sure that modern bombs actually use the fast neutron fission of the fusion tamper/jacket. It does add significantly to yield, but it also makes the weapon extremely dirty. And the fusion stage _does_ create a significantly larger yield by itself, independent of tamper fission- the typical ratio for a fission-fusion-fission bomb is 50% fusion, 50% fission from what I’ve read. So even if you only get half of the maximum yield, a 50 kt “clean” bomb where at most 20% is derived from fission (10 kt for the full primary) is a LOT more useful politically and militarily than a 100kt bomb that’s considerably dirtier. Still, I do agree that at best, Tyson was omitting a lot of caveats and details, and at worst was just full ot shit. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [November 4, 2022, 4:22pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/39 "2022-11-04T16:22:59Z")
> [@bump](#): > > So even if you only get half of the maximum yield, a 50 kt “clean” bomb where at most 20% is derived from fission (10 kt for the full primary) is a LOT more useful politically and militarily than a 100kt bomb that’s considerably dirtier. > > Still, I do agree that at best, Tyson was omitting a lot of caveats and details, and at worst was just full ot shit. As noted above, your assumptions yield the equivalent of a 10kt fission bomb, which is roughly the same as a Hiroshima bomb. This is plainly the opposite of Tyson’s statement that modern bombs “do not have a radiation problem”: > [@](#): > > Neil deGrasse Tyson quickly responded, saying, “…modern nukes don’t have the radiation problem just to be clear.” > > “You still blow to smithereens”. Modern nukes are a different kind of weapon from those used in Hiroshima and Nagasaki. > > “Nuclear weapons if they’re exploded don’t have a radiation problem?” the host asked. > > “Not if it’s Hydrogen bombs, no,” Tyson confirmed. The most reasonable explanation for what Tyson is saying is that he understands fusion very well, and he understands that its reaction products aren’t highly radioactive, but (like most laypeople) he doesn’t know that most modern nuclear weapons are at least halfway fission bombs, and produce the same amount of nasty stuff as a Hiroshima bomb (if not more). I read this a few days ago so it’s still under my skin, that’s why I’m a little obsessed with correcting the record. Not least because it gave that idiot Bill Maher another thing to be smugly, conspicuously wrong about. But we at least can do better. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [November 4, 2022, 4:36pm UTC](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168/40 "2022-11-04T16:36:33Z")
FWIW, this Wiki article talks about tampers in nuclear and thermonuclear weapons design. > **[Tamper (nuclear weapon)](https://en.wikipedia.org/wiki/Tamper_(nuclear_weapon))** > > A tamper is an optional layer of dense material surrounding the fissile material. It is used in nuclear weapon design to reduce the critical mass of a nuclear weapon and to delay the expansion of the reacting material through its inertia. Due to its inertia it delays the thermal expansion of the fissioning fuel mass, keeping it supercritical for longer. Often the same layer serves both as tamper and as neutron reflector. The weapon disintegrates as the reaction proceeds and this stops the rea... There are several viable candidates for a non-fissile tamper with good density and inertia. It’s just that intentionally designing a weapon to decrease its fallout (at the expense of minimizing its yield with respect to its throw weight) only makes sense in selected applications. I found it interesting that the nuclear weapons for the SPARTAN anti-ballistic missile were designed with a tamper of gold, which would enhance the weapon’s output of X-rays (to incapacitate inbound warheads’ control electronics). [Previous page](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168.md?page=1) [Next page](https://boards.straightdope.com/t/deaths-from-a-400-kiloton-nuclear-explosion/974168.md?page=3)