At a war museum in Manchester England, there is a training example of a WE177 British free-fall nuclear bomb that had a yield of 400 kilotons. The information panel says this about deaths from a hypothetical explosion over the city:
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?
Any answer that says “entire population dead” within a certain range is bound to run into fuzzy real-life factors. For instance, some people might be deep underground, etc.
I ran a 400 kiloton ground burst simulation on NukeMap
100% fatality no matter what radius was 2.06 km, which is about 1 and a quarter miles. More specifically, incapacitating within 5 minutes, death in 4-6 days (unless, of course, you were vaporized by the fireball. In which case you don’t have to worry about radiation sickness).
Out to 1.35 miles most will die within a month but some may survive.
Out to about 1.75 miles you’ll likely get some radiation symptoms but 95% survive.
That’s just for radiation though, and doesn’t take into account the fireball, blast effects, buildings collapsing, fires, and so forth. The radii for, as an example, burns are considerably different than for radiation.
Estimated numbers of fatalities for a given configuration of variables for a particular target can be caculated. You can also use current location weather for the fallout effect.
NukeMap is here. It also allows you to model fireball, blast effect, choose surface or airburst, etc.
Have “fun”.
The different sorts of hazards also differ considerably in what is sufficient to shield you from them. For gamma radiation, you’d better have a few meters of something between you and the nuke (which could happen even very close to the center, if you’re underground). For the thermal bloom, drywall might be enough (though you’d probably want to evacuate quickly, before fires could spread).
400 kilotons (0.4Megatons) is a HUGE bomb. Hiroshima is variously described as from 8 to 20 kilotons (IIRC the more agreed on number is 15). the other question is height. Hiroshima was set off 2000 feet high. Much of the physical damage was blast shock-wave related. (Although the famous Peace Memorial’s dome skeleton at ground zero survived because the flash vaporized the copper sheeting, leaving only the much stronger iron beams to resist the shock.) Part of the problem was that some of the wide firestorm was a result of using fires for cooking, that set the collapsed buildings on fire. Nevertheless, the radius of destruction was about 1 mile. Make a bomb 20 times bigger, odds are the radius will be almost 4 miles or more, using a back of the envelope inverse square guess.
If everything is flattened within 4 miles and probably even more, does it really matter what the radiation does is for those within that range?
There are considerable differences in the effects of airburst vs. ground detonations.
Take the historical Hiroshima detonation. I won’t nitpick that the detonation was actually reported at 1900 feet rather than 2000 as I don’t think that makes any significant difference here. (I also Nukemapped it at 20 kilotons for a nice, round number)
With the BOOM at 2000 feet the actual fireball never even reached the ground at Hiroshima. If it had, the Peace Dome would have been vaporized instead of “just” heavily damaged. The radius of total destruction was, yes, about 1 mile due to combined effects, but Nukemap wouldn’t even give me a figure for overpressure above 5 psi because the fireball was just too high in the air for that. Radiation injuries don’t quite reach one mile, and the “certain death” ones are in about a 2/3 mile radius from ground zero. The bigger problem with that scenario is the likelihood of burns from thermal radiation (a.k.a. “heat”) which, for 3rd degree burns extended out to a mile and a half and for second degree out to 1.78 miles. Yes, a lot of people got radiation sickness, but that was along with severe burns and the combination is more deadly than either alone. Further complications were that Japanese building construction tended to be lighter than that features in the West which meant that buildings were more likely to be flattened.
Detonate a 20 kiloton bomb on the ground, though and you’ll have a ring of 3000 psi overpressure of 90 yards, which will pretty much reduce anything but a hardened missile silo to gravel or dust. Not that it matters, because the frickin fireball will have a 260 yard radius and everything within it will be turned to vapor. Everything not a heavily concrete building out to 1/3 of a mile will be destroyed, out to 3/4 of a mile most if not all buildings will collapse. But wait! There’s more! Anyone within 1.2 miles WILL get third degree burns (unless heavily shielded from heat effects). Out to a mile and a half from ground zero you get 2nd degree burns. Oh, and it’s with a ground burst you get serious fallout, much much more than with an airburst. So there are some important differences in effect from airburst vs. ground.
Do these differences matter? Maybe. Modeling these things is complicated.
And while on a certain level 400 kilotons is a “HUGE” bomb, there are much much bigger bombs out there which is why we have a rating called “megaton” for the really big boys. Tsar Bomba was 50 megatons, or 50,000 kilotons. That generates a fireball just under three miles wide, with an airburst flattens everything within 15 miles, causes third degree burns in a 36 mile radius, and so on and so forth. The Russians might have a bit more detail from their one and only test of it, but they aren’t sharing.
The “flatten everything” ring for a 400 megaton surface detonation is actually more like 2 miles. Of course, to someone on the ground that may not be a meaningful distinction. For an airburst you don’t get quite the same intensity but still a lot of knocked-down buildings out to about 3 miles. Again, though, what with fires breaking out, burns from direct thermal radiation, and the like I’m pretty sure anyone not immediately killed or incapacitated will not be taking detailed notes within those areas.
Does the radiation matter? Not to people at ground zero - their problems are over. But towards the outer edges of the blast/heat/whatever effects? Yes, yes it does. Aside from radiation injuries you’re going to have a lot of other injuries from falling stuff, flying debris, broken glass, high temperatures, etc. Radiation impairs the ability of the body to heal and resist infection. Injuries you might otherwise survive and recover from will kill you if you also have significant radiation exposure on top of that. Even if you do survive mundane injuries significant radiation exposure will make your healing take longer, you may not heal normally (keloid scars are quite common based on data from Hiroshima and Nagasaki) and possibly cause problems with reconstructive surgery.
So yes, it does matter to at least some, even if not to all.
I recall reading that the 50-megaton city-leveler would start forest fires in the forest 50 miles from ground zero.
I guess one statistic it would be nice to know would be - at what point would being behind standard solid concrete construction (10 inches?) give you a passable level of radiation protection?
The other point is that a ground burst would I assume mean a lot less destruction because the material in the immediate surroundings would to some extent limit the effects further out? A lot less line-of-sight destruction?
That would completely protect you from alpha and beta radiation, it’s the gamma that would be the big problem. 10 inches of concrete will diminish gamma, but not completely block it. Think of progressively thicker panes of slightly tinted glass. One pane barely changes the light going through it. 10 panes will have a definite effect, but not completely block light. And so on.
A quick google says it takes about six and a half feet of concrete to reduce gamma radiation by a factor of a billion - at which point it’s a question of just how much gamma you’re dealing with. At which point we’ve exceeded my physics knowledge and math ability.
10 inches of concrete will reduce the amount of radiation you receive, hence the recommendation by various authorities that you shelter as deep inside a building as possible if you’re in an affected area. Depending on circumstances, that might shield you sufficiently to avoid overt symptoms, or reduce a lethal dose to something you might survive, but the exact calculations, as I said, are beyond me.
Again, many complications. A ground burst on a mountaintop will have different effects than a ground burst in a deep valley due to the landscape either containing or not the forces involved. Buildings with a heavy, solid construction will “soak up” much of the force when they’re knocked down, in essence shielding structures further out as well as soaking up thermal effects. Airbursts are less constrained, having a greater area of impact, but within that area destructive forces are diminished due to having to travel through the air first. Again, we’re getting beyond my ability to make calculations.
None of this will change the outcome for people at ground zero - they’re dead, vaporized. What it changes is the level of destruction/death at distances from the center of destruction.
If you say “hypothetically, I’m 5 miles from ground zero what variable affect my survival?” that is probably something that could be calculated, but a lot would depend on whether you’re in an urban or rural area, and whether or not you’re under a fallout plume.
(never mind)
400 kilotons is pretty hefty. A 20 kiloton device is big enough to wipe out, say, Denver, so I’d say the specs given are pretty accurate. However, Velocity’s “real life factors” always have to be taken into account.
Very few buildings are built with solid concrete of any thickness. So if your question is about concrete’s inherent gamma attenuation ability, @Broomstick gave a great answer. But if it’s really “How safe am I in a typical concrete building?”, the answer is probably “Less safe than @Bromsticks excellent answer suggests at first glance”.
Many modern warehouse & light industrial park buildings are made of concrete panels. So called “tilt-up construction”. But they’re typically more like 6" thick. And don’t have good blast resistance, so are likely to cave in with only slight blast overpressures. OTOH, if they stay standing, they are fully attenuative for whatever their thickness is.
Most other mid-rise “concrete” buildings are holl=w concrete (“cinder”) block construction. Or are a steel skeleton with poured concrete slab floors / ceilings, and metal/glass exterior curtain walls. If there is exterior concrete, it’s likely again to be concrete (“cinder”) blocks. Whose cavities are not filled with poured cement for weight reasons.
Punchline: a finished cinder block wall may look like concrete and it may be 6-8" thick, but it’s barely 2" of not-very-dense aggregate and the rest is air.
Actually, in some respects, the interior of an elevator shaft might be your best location for improvised shelter and it would have the thickness of the exterior walls, the air in the interior spaces, and also the thickness of the shaft walls… except it would probably provide little overhead protection. Provided you can fill the elevator car with sufficient shielding (doesn’t have to be concrete, but it does have to be dense) and then shelter under the floor of the car… except I don’t think there’s a feasible way to kludge all that together in time for it to provide meaningful protection in a fallout situation. (Assuming you’re not in a Certain Death and Fire Zone, latest I’ve seen is an estimated 15-20 minutes before the fallout starts falling… but there’s a bajillion variables there, too)
But @LSLGuy’s post is also excellent.
Plus, good luck getting out of the elevator shaft afterwards.
Depends on whether or not there’s a basement-level access of some sort, or if a ladder is available, or…
Hey, no one said surviving a nuclear emergency would be easy.
The construction I recall (back when the city was non-stop high-rise apartment construction) was poured concrete walls (and floors) between the suites for fire break, and the outer ends of the suites were open for a panel finish (or nowadays, a lot of glass). However, the majority of the suburb houses are wood frame, and one-story warehouses are as mentioned, fragile easily toppled concrete block. (Every so often there’s a new item of such a wall under construction falling or being blown over by the wind). Many more modern buildings just use pillars, and the rest is open. So the question is what type of construction and what orientation to the blast. If you are in a middle apartment in a high-rise end on to the blast, you could have several feet of concrete between you and the radiation source.
The Nagasaki blast was apparently about 2 miles off intended target, and again a low air burst, so the nearby hills protected some of Nagasaki from the worst of the blast.
Fallout (and residual radiation) is a whole different question. Both those bombs were air bursts, so did not immediately involve a lot of debris being irradiated, and what there was was dispersed widely. I presume a ground blast would shower the vicinity with tons (megatons?) of irradiated debris from the crater created. The fallout shelter logic, IIRC, was that within 30(?) days most of the worst isotopes would have decayed and it would be safer to emerge. Also note that with wind patterns the fallout could affect a large area - there were reports of radiation burns for people outdoors in Belarus and Poland from the Chernobyl incident.
I watched the Duck and Cover film. I’ve got this.
Except… there were survivors in Hiroshima that were within 1000 feet of ground zero. And they lived for decades.
There are no absolutes.
And don’t break your thick glasses. You can’t read without them.
400kt is squarely in the strategic weapon range, albeit not a particularly large warhead in terms of what has been detonated in the past (tens of megatons).
US nuclear weapons range from 0.3 kt on the smallest yield of a B61 bomb, all the way up to about 1.2 megatons on the B83 strategic bomb. Our ballistic missiles are about 400-475 kt, and the Tomahawk/ALCM warheads are about 150kt.
So it’s a big bomb by today’s standards, but that’s more because larger bombs are more problematic to deal with all around, and with our drastically enhanced accuracy, we can use smaller, easier to deal with bombs to achieve the desired effects.