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For reference, here is a type of safe I am talking about: a Liberty quality gunsafe. Gun safes are extremely strong, they are on the more expensive end made with solid steel plates. But I am unsure whether something like that could survive nuclear war.

The worldbuilding context is that nuclear war happened, but some artifacts survived from ww3. But any artifact that I know of that is part of us daily life, like laptops, watches, toys, etc is not strong enough to survive global thermonuclear war. So it wouldn't be realistic for them to survive in any capacity. Then I thought, what about a safe. But I am unsure of the relative power of the nuclear stockpiles and of the durability of the leading consumer/civilian gunsafes.

Would it be plausible for a safe like the one above which is made of steel or a similar or weaker material to survive point blank sustained nuclear blasts?

A note: please derive your answers from the premise that it is a direct impact/blast, where the nuclear blast is within 9 yards of the safe. Also base your answers off of the assumption that the safe is in a standard consumer house, with no additional protection and not being underground.

I think that the safe will be disintegrated, but I do not know enough about material strength and nukes other than what is in movies.

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    $\begingroup$ A lot of the discussion here is very similar to Could a Tank Survive a Nuclear Blast? $\endgroup$
    – Wyck
    Dec 16, 2022 at 14:15
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    $\begingroup$ It will not survive. Look at early nuclear tests. The test rigs are disintegrated. $\endgroup$
    – Tony Ennis
    Dec 16, 2022 at 15:20
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    $\begingroup$ Top answers very thoroughly point out 9 yards is too close and anything will be vapourised. But why 9 yards? If the underlying question is about how many guns will survive a thermonuclear war, consider that most gun safes will not be anywhere near that close to any blasts. The worlds active launchable nuclear weapons measure in the thousands, not the millions. (And many firearms are stored underground, in residential basements, police/military storage rooms, etc). $\endgroup$
    – MGOwen
    Dec 17, 2022 at 0:34
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    $\begingroup$ Why on Earth would any part of the world being bombed so intensively that a majority of the territory within any given few square miles was within nine yards of ground zero. Nuclear bombs destroy cities; even the largest cities around would be thoroughly destroyed by a single MIRV missile, dropping maybe a dozen warheads across the area of the city. The vast majority of the territory would still be well over nine yards from any of the grounds zero. $\endgroup$ Dec 17, 2022 at 17:40
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    $\begingroup$ No real point in reopening this closed question, but the high quality, interesting answers is generated shows why it was a good question, and deserves those upvotes (and why it was a bad idea to close it). The superficial answer is obvious ("no") but the details are fascinating! $\endgroup$
    – JamieB
    Dec 26, 2022 at 19:37

6 Answers 6

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As specified, this question is trivial - you're saying that a thermonuclear weapon is going off within nine yards of the safe.

Though there's variation, a relatively typical thermonuclear weapon in modern arsenals is ~100kt, so we'll go with that. Such a weapon has a fireball radius of 170m, so at nine yards, the safe will be well within the fireball radius.

Now, explosions are tricky things. It's not entirely impossible that debris might strike the safe and fling it away, allowing some mangled remains of the safe to survive. It would not look like a safe anymore.

Otherwise, if the safe is engulfed by the fireball, no firesafing is capable of withstanding tens of millions of degrees; the safe would be vaporized. No trace of it would remain. A 100kt explosion has an approximate energy release of 4.1 petajoules; the enthalpy of vapourization for iron is ~350kj/mol, or 6kJ/g. Though it's unrealistic to assume all that energy could be used strictly to vapourize iron, that means that it could, theoretically, vapourize 683 thousand tonnes of iron.

Most of that energy goes elsewhere. But more than enough of it sticks around to erase a gun safe from existence.

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    $\begingroup$ A regular safe I think is less then 1 ton. So by this calculation, it would seem that 683 thousand+ safes would be disintegrated by a single nuke. $\endgroup$
    – Sixoca
    Dec 14, 2022 at 17:01
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    $\begingroup$ @Sixoca Could be. Most of the energy goes into the blast wave, or is emitted as radiation. When the overkill is this ridiculous, however, that doesn't matter. $\endgroup$
    – jdunlop
    Dec 14, 2022 at 17:29
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    $\begingroup$ @Sixoca You'll have to find a good reason -and most importantly a way- to put 683 thousands and 22 safes in the same 9-yard space first :p. $\endgroup$ Dec 15, 2022 at 0:10
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    $\begingroup$ I disagree with the idea that debris dislodged by the blast would knock the safe away. At this distance, the HEAT (which travels at C instead of the speed of sound) would vaporize everything in between and then the safe. $\endgroup$ Dec 15, 2022 at 14:17
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    $\begingroup$ @Fattie If the fireball instantly came into existence at that size, then maybe. Unfortunately for our poor target the energy is streaming outwards from a small locus only a few yards away. Which means that most of the energy for a conic section of that fireball is trying to pass through the space occupied by our hapless gun safe... significantly more than 1e-6 of the power at any rate. $\endgroup$
    – Corey
    Dec 16, 2022 at 3:52
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Steel may not remain solid within meters of a nuclear explosion

  1. The safe is not “extremely strong” at all. The model is likely Liberty Safe Co.'s Freedom 30. According to the specs, the save is constructed from 14 gauge steel sheet, which is slightly under 2mm of thickness. There is a layer of thermal insulation rated for 40 minutes in a 1200°F, or 650°C fire. The mass of the safe is 200kg. This is rather an entry-level safe, satisfying most U.S. states minimum requirements for a gun safe.

Evidence from the Trinity test

  1. For comparison, the steel tower of the Trinity test was 30m tall, mounted on a rebar-reinforced concrete foundation. I could not find the construction documentation, but it was obviously constructed from very much not 2mm-thick steel. The photograph below shows that each of the four main weight-bearing columns were square extrusions with a cross-section somewhat larger than an adult man's thigh, about 500mm. Extrusion profile is unknown, but we can safely put the thickness of the extrusion wall at 75mm. This yields the estimate of steel cross-section at 1300 cm², and each column's mass, assuming steel density of 7.9 g/cm³, 1300×3000×7.9=31 metric ton. Adding the cross-tie members of the tower, we can estimate the total mass of the steel construction to in the 200‒300 ton range (1,000 to 1,500 of “extremely strong” safes).

Trinity tower foundation close-up Trinity tower foundation close-up

Trinity tower full view Trinity tower, full view

  1. The Gadget was detonated on top of the tower, with the yield later estimated at 21 kt TNT equivalent. The tower has evaporated completely, according to the U.S. DoE. The annotated image of the fireball at 25ms after detonation shows the scale of the fireball. Note that the heating front had not yet been overcome by the shock wave adiabatic expansion front, which means that at this point the thermal radiation from the compressed air fireball core was still ongoing (v. infra), and the temperature and pressure at the fireball periphery had been increasing.

Annotated fireball profile at 25 ms Annotated fireball profile at 25 ms. The scale bar size equals 100m.

  1. While most of the concrete foundation also either evaporated or remelted with the surrounding sand, a few rebar ties of one of the concrete pillows have partially survived. Molten and recrystallized sand surface is clearly visible.

Surviving rebar ties Surviving foundation rebar ties

Rough theoretical analysis of fireball conditions

Dynamics of a nuclear explosion is analyzed in (Glasstone), while (Brode) additionally elaborates on the thermodynamics of the early internal fireball conditions.

After the energy is released by the nuclear device on the order of fractions of a microsecond, its X-ray part of the spectrum radiatively heats surrounding air. Cold air is opaque to X-rays, and is radiatively heated up to the temperature of about 1,000,000 K, at which point it becomes transparent to this part of the spectrum. The hot ionized gas at this temperature is itself a source of X-rays; this mechanism forms an expanding heating front of the fireball, isothermically propagating outwards, until the temperature drops to 800,000K, when the plasma loses thermal equilibrium with the X-ray radiation, and becomes confined to the outer opaque shell of air. This process is significantly faster than the adiabatic propagation of the shock front of expanding gas, due to the gas inertia, and dominates the fireball up to 75 μs since the explosion, reaching the radius of about 30 m from the explosion. From this point onward, the heat front propagation races against the adiabatic expansion of the hot gas. In the Trinity case, the last frame showing the expansion of the heat front is timed at 25 ms from the explosion. At this time the adiabatically expanding and cooling ball of gas overcame the radiative heat front, and temperature and pressure began to drop significantly.

The steel construction readily absorbs the thermal X-ray radiation, and, partially, γ-radiation: HVL=2.2 cm in pure iron for Co-60 γ-source (Johnson), which puts the absorption figure at about 50%, pre-heating if not melting the bulk of material from the initial intense γ-pulse. This combined radiative heating causes quick ablation of material, with the entire tower material undergoing more likely a supercritical phase transition than evaporation, on the time scale of 100-1000 μs, well within the intense thermal radiation-dominated, high-pressure fireball state, persisting for about half the time of the observed shift to adiabatic regime at 25 ms since the detonation, i.e. ~10 ms. The wide estimate range reflects a multitude of unknown and hard to account factors in this test, but still, even conservatively, is under an order of magnitude of the timespan of the required environment conditions.

References

Brode H. L. A Review of Nuclear Explosion Phenomena Pertinent to Protective Construction. R-425-PR. RAND Corp., May 1964.

Glasstone S. (ed.) The Effects of Nuclear Weapons, rev. ed. U.S. DoD, U.S. AEC. April 1962.

Johnson T. E., Birky K. B. Health Physics and Radiological Health, 4th ed., Wolters Kluwer, 2012

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    $\begingroup$ +1. tl;dr: the safe doesn't just melt or even just evaporate, it gets so hot so quickly that it undergoes a supercritical transition and turns into vapour instantly, adding its own little mini explosion to the giant one surrounding it. $\endgroup$
    – N. Virgo
    Dec 16, 2022 at 14:13
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    $\begingroup$ @N.Virgo Supercritical fluid is a technical term, a state of matter that is neither liquid nor gas. It exists above critical point. both temp and pressure. S.c. CO₂ is widely used as solvent for dry cleaning and extracting caffeine from beans. For iron tho, the critical pressure has not been measured, only predicted in the range 4–7×10³ bar, and T≈9–9.5×10³K. The pressure in the fireball drops from ~70×10³ bar in the isothermic regime down to ~7×10³ bar by ~10ms, the time of isothermic to adiabatic transition. This is exactly the upper bound of s.c. iron, when it could melt and vaporize. $\endgroup$ Dec 16, 2022 at 15:50
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    $\begingroup$ @N.Virgo In a supercritical transition, latent enthalpy degenerates to zero. Normal liquids need a lot of heat to boil off, but above critical pressure, only the specific heat capacity is important; as soon as solid is heated above critical temp., it turns into this fluid phase with only latent enthalpy of melting at play. At s.c. pressure, less heat is needed to “evaporate” matter. The density of s.c. iron is est. 2–3 g/cm³, 2-3 times heavier than water, not quite a gas! Here's a couple of videos about s.c. CO₂: lab demo: youtu.be/JslxPjrMzqY more theory: youtu.be/eyn7MusdQ9g $\endgroup$ Dec 16, 2022 at 16:11
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    $\begingroup$ Oh ok. Somehow I got "supercritical" mixed up with "superheated". It being a supercritical fluid makes sense. Either way the safe is not having a good time. $\endgroup$
    – N. Virgo
    Dec 17, 2022 at 0:23
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    $\begingroup$ @JamieB, the answer is not so obvious: “it goes kaboom and puff“ is not the answer Move the safe 500m away, and physics will be different. Not the safe's fate—the physics of its demise! Too bad it was closed. Not a good question, but the Q about hard science of a (thermo)nuclear explosion is not that bad. Agree 100%! $\endgroup$ Dec 27, 2022 at 7:37
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So, we have some answers based on the Hiroshima Bombing, though the Hiroshima Bomb is woefully small compared to what would be used in full on global thermo-nuclear war. The closest structure to the explosion is the famous Genbaku Dome, which survived more as a matter of being directly under the blast, which melted the copper metal dome, allowing the actual blast to be pass through the structure, and exit through ground level doors and windows little damage to the structural integrity. It was 150 meters from Ground Zero and there were no survivors from inside the building. The closest survivor to the attack was 170 meters from the blast and was in his basement at the time of the attack. The closest survivor to the hypocenter (the center of the blast according to seismological data) was 300 meters from the hypocenter, a woman who was in the vault of the bank at the time of the explosion. Most structures that survived were those that were re-enforced to survive earthquakes.

For a gun safe to survive with it's contents intact, it would first need to be stored in a place that would not be line of sight direction from the blast. Otherwise, the intense heat from the light would likely melt it, and failing that, the heat may cause the ammo inside to discharge inside the safe. That said, the guns themselves will survive, but as the saying goes, "Guns don't kill people. Bullets kill people."

That said, if the safe isn't in the direct light of the blast (and close enough to the fires from things that are, you now face the overpressure. Good news the fires are suffocated and thus go out. Bad news... the structure is now being hit by enough pressure force to rip structures off foundations and level buildings within a radius of several miles unless re-enforced. If your safe is not bolted down or below the ground, it's probably going to be gone with the wind. It may survive that... but the contents will be banged up. If it is secured enough, at this point, it's probably a good place to keep things safe. Assuming the bullets inside didn't misfire and the overpressure wave would get in the way.

If it's an electronic safe, there might be an issue with getting it open because of the EMP frying unshielded electronic devices. If you know the attack is inbound, getting electronic devices into a faraday cage will protect them and most houses in the U.S. have at least one that you can fit some laptops, tablets, and cellphones into if you get enough warning. Afterall, what do you think that wiring mesh on your microwave's window is for? Decoration? So long as you aren't an idiot and turn the microwave on with your electronics inside, they will work after the bombs start falling, provided you are far enough away that radiation is your next concern. Though don't expect them to do much beyond the battery life you have on them (The going theory is that a large scale attack on the U.S. will include one Nuke detonated at an extremely high altitude somewhere over the geographic center of the nation. The EMP from this one nuke would fry most electronics in the lower 48. So you will likely not have power for a recharge for them AND probably won't have cellphone service either. But you have your Angry Birds for the rest of the battery life!).

One of the best known structures for surviving a direct nuclear attack is the Cheyenne Mountain Complex, a major U.S. Airforce Command and Control bunker designed to survive a near-direct nuclear attack (most nuclear missiles are not precise because the likely range of error would still leave the target in the blast radius of the nuke). It's estimated that at the height of the Cold War, the U.S.S.R. had enough missiles pointed at this thing that it would be directly hit with an explosive force of 1 Gigaton of TNT (the largest yield of a single bomb is 50 megatons, and the bomb itself was so large that using it as a weapon was infeasible).

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    $\begingroup$ If a human can survive 170 meters from the blast and in a basement, a rifle would be fine. $\endgroup$
    – Mazura
    Dec 15, 2022 at 1:31
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    $\begingroup$ @Mazura a human being able to survive 170 yards from the blast does not imply anything whatsoever about a rifle (or anything) 9 yards from the blast being fine. $\endgroup$
    – Peteris
    Dec 15, 2022 at 1:54
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    $\begingroup$ 9 yards is significantly closer than 170 yards, especially taking inverse square law into account... $\endgroup$
    – Aron
    Dec 15, 2022 at 10:09
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    $\begingroup$ @Mazura The closest surviving structure was 150 meters. Keep in mind that if the gun safe is in direct line of sight from the blast, it will probably melt and even then the intense heat of the ensuing fire would likely cause any ammo to misfire inside the safe. The light from the flash of a nuclear. And that's one person in 170 meters in a very situational position... The Hiroshima Bomb was dropped on the Urban Core of the City at 0815 JST, which meant morning commute was well underway. $\endgroup$
    – hszmv
    Dec 15, 2022 at 16:06
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    $\begingroup$ "Photo No. 23. H I R O S H I M A . Shadow cast by valve-wheel on side of gasholder [1.25] miles from the centre of damage. The bitummous coating on the steel plates was affected by heat radiation except where shielded by the wheel and spindle." I'm just looking for the sweet spot. If the title had 9y in it, I'd've ignored it completely.... 170 meters in a basement, or possibly 1.25 miles, out in the open (it burnt the paint on a pressure vessel... with that kind of wall thickness tho; might need an actual safe). osti.gov/servlets/purl/4430289 $\endgroup$
    – Mazura
    Dec 16, 2022 at 1:47
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Extremely unlikely

Nuclear bombs such as the one who fell in Nagasaki and Hiroshima leveled out buildings kilometers away from the epicenter, and those bombs are considered to be weak nowadays1. Some of these were made of reinforced concrete, and on some you could see very well the iron structure bent by the blast2.

The closer you get to the blast center, the higher the pressure and temperature gets. Even if your safe is made of 50cm deep layered steel walls, it won't stand the blast at point-blank range. In fact, some people already blew up safes with much, much less power than those of a nuclear bomb3.


1 : Nagasaki and Hiroshima suffered blasts of around 21 and 15 kilotons of TNT, respectively. Modern bombs tend to have much higher yields, ranging in the hundreds and thousands of kilotons. Source : Wikipedia and this list of USA bombs
2 : You can find pictures of it online, such as the tests made for the trinity project here (full source here, ⚠️ some photos are not for the faint of heart!).
3 : And much other things, including cement-full trucks with only conventional explosives. You really don't need that much power to blow things up!

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  • $\begingroup$ I had no idea that cement could be blown up by regular explosives. I do wonder though, if cement is like concrete, why are bunkers said to be safe? If they are deep underground they might be, but those bunkers in people basements don't seem like they would be very reliable upon reading your answer... $\endgroup$
    – Sixoca
    Dec 14, 2022 at 17:03
  • $\begingroup$ @Sixoca It's both a matter of distance and medium propagation (indirectly line of sight). First, power can be divided by a good square of the distance under a constant medium, if not more (I need to find back the exact formula though :) ). Then, as you can see on wikipedia, blast heat and pressure can get heavily reduced/reflected if they traverse the wrong mediums (e.g. : water or land). It's why it's best to hide your bunkers afar from priority targets like city centers. The closer you are, the less likely anything will survive. $\endgroup$ Dec 14, 2022 at 17:18
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    $\begingroup$ @Sixoca - a bunker in a basement wouldn't survive at ground zero. But five kilometres away from ground zero, while the building above it might be scythed down by the blast wave, but people in the bunker would be safe. From the initial blast, anyway. $\endgroup$
    – jdunlop
    Dec 14, 2022 at 17:30
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    $\begingroup$ @Sixoca you didn’t know that concrete could be blown up by regular explosives? Did you think explosive demolition was done with nukes? Have you seen a photo of… any war after 1900? $\endgroup$
    – Daniel B
    Dec 14, 2022 at 18:44
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    $\begingroup$ @Sixoca - the ones that were built correctly are fallout shelters; you have to live through the blast, then comes the hard part. Being underground or having 4' of concrete (cement is uncured concrete) above definitely helps with that. As does living in say, Iowa. Very few people in cites ever had one; primary targets have no time to get to them. If you're in Minnesota and the news says NY is gone, then it's time to go downstairs and put sheets over the windows. $\endgroup$
    – Mazura
    Dec 15, 2022 at 1:40
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There are all sorts of atomic bombs. It is hard to get your conventional A-bomb to detonate with less that 0.5 kT. There were calculations done to see what detonations might be possible to avoid the test ban treaty, using very small bombs, surrounded by crushable material (gravel, coke) to break up the characteristic P-wave shock. The only things you might be able to hide were too small to stand a reasonable change of a predictable yield.

You could make a bomb out of something with a shorter half-life. There were theoretical studies on using Californium, with a critical mass of 20g, for a nuclear rifle bullet. You would have to make your ammunition, but it seemed feasible in the fifties/sixties. Never built as far as I know. But everything between that and the Tsar Bomb are 'thermonuclear weapons'.

Why 9 yards? If you are aiming at buildings, you would use an airburst weapon. The shockwave reflects off the ground, and the wave and its reflection form a single shockwave, called a Mach stem. The overpressure of this shock wave is what brings down buildings. This is why the Trinity test was put in a tower. If you put it higher, you can avoid fallout. So, are we above, or below or to one side of the bomb, and why?

I would have thought for every gun in a safe within 9 yards of the detonation that is very unlikely to be in a fireable state, there would be three million gun safes buried in collapsed buildings 9 miles from ground zero, and some of them would survive.

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Short answer: No.

Longer answer - Within 9 yards of a Thermonuke? I'm fairly certain that the safe would be turned to Plasma near instantaneously.

First reference is this: Liberty Safe Torture test with Det Cord

It's a torture test of a Liberty safe and a competitor safe, they appear to just be using DetCord - the Competitor safe performed badly, the Liberty safe held up. But we must now put this in perspective, they used maybe a Kilo? of conventional explosive. The smallest conventional nuclear explosive (W54 warhead) had a yield at it's lowest of 10 kilotonnes of TNT.

The smallest Nuke (not a Thermonuke) is 10,000,000 times more powerful than the above YT test.

Another explosion to put this into perspective is The Halifax Explosion which is when a cargo ship carrying munitions exploded in Halifax, Nova Scotia, Canada - with an estimated force of 3 Kilotons of TNT (again, 1/3rd the smallest possible conventional nuclear yield) - The only bits that survived somewhat intact where her 90mm Gun and her Anchor fluke, both would have been made of Steel and both would be significantly heavier and denser than the steel used in a Consumer grade Gun Safe. The website for Liberty give a weight of a high-end consumer grade safe of approximately 300 Kilos, whereas the Gun barrel from a 90mm naval artillery piece weighs about a tonne and the Anchor from the blast weighs about half a tonne.

And again (I must stress) that this explosion was with conventional explosives that where significantly smaller than the smallest nuclear explosion.

We are also not factoring in the differences in explosions between Nuclear and Conventional explosives - specifically the Fireball from a Nuclear explosive is several million degrees, it is literal Plasma - whereas a conventional explosive of a similar kilotonnage does not have the same intense heat that a Nuclear device produces, even if the blast wave propagation is functionally similar.

The only scenario that is within the realm of possibility would be a Gun Collector who built a strong room in the basement of their house, a few hundred meters away from a Thermonuclear blast. Such collectors do exist outside of the US and often prefer a dedicated strong room as they are functionally harder to break into than a mere safe.

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