I know there is a concept in nuclear weapons called critical mass in which a certain amount of weapons-grade fissionable material is needed for a nuclear explosion. I know that such explosions are measured in terms of kilotons (or megatons) of TNT.l I do not know what is the smallest such explosion possible, and that is the question I am asking today. Thank you.
According to the Davy Crocket article, the yield of that weapon was between 10 or 20 tons of TNT (0.01-0.02 kilotons). It says this is near the minimum practical yield for a fission weapon.
Would that overlap with any of the strongest possible conventional explosives? Apologies for not checking out Wikipedia as I’m on mobile.
I think it was uois SLotlin who killed himself with a screwdriver and a bunch of fission material. The theory is that it could have been a lot worse if he hadn’t acted quickly.
In Sum of All Fears (the book, not the movie) by Tom Clancy, the author posits a poorly constructed A-bomb that fizzles, barely killing anyone beyond the confines of the Superbowl Stadium.
A chain reaction happens when a critical mass of fissionable material is brought together. What constitutes a critical mass and how long it takes depends on a number of factors - the purity of the material (different isotopes are more or less susceptible to splitting and releasing energy and other particles) and how long the the mass stays together, considering part of the result of the release of a massive amount of heat in a short time is, of course, explosion. The fizzle in *SoAF * is a result of the fission material dispersing before enough neutrons were released and able to split enough fissible material.
The first nuclear test by North Korea was also reported by some to have fizzled and failed to produce even a kiloton explosion. 2006 North Korean nuclear test - Wikipedia versus 12 to 20KT for the first American bombs.
So it depends…
The Americans also had designs for artillery-based battelefield nukes, which presumably would be fairly low yield… Pls, the neutron bomb design was basically a nuke that fizzles, producing a flood of lethal neutrons rather than a large heat-and-shockwave explosion. The lethal effects would be felt for a longer distance, while the explosion would not be much more than a large conventional bomb. Neutron bomb - Wikipedia - however, this article says the explosion would still be a kiloton range.
The problem with any device is self disassembly - once you reach critical mass the lump of fissile material will blow itself apart stopping the reaction. That is essentially what happened in the Slotin accident. The yield is so low that a fire cracker probably makes more noise. A weapon tries to maximise the yield with a whole range of techniques, the main one being explosive containment - where there is a conventional explosive whose job is to compress and contain the fissile mass for long enough that the reaction can proceed far enough to get a useful yield. The longer the better. The better you do this the higher the yield, and conversely the worse you do this the lower the yield all the way down to a device that does little more than blow itself apart. Because the reaction is exponential the time contained makes a huge difference. You could probably come up with a theoretical minimum yield based upon no confinement and a minimum fissile (i.e. just critical) mass so that only the inertia of the material is involved in keeping it together. As Slotin found, the neutron flux will kill you, but the explosive yield is essentially zero.
It seems that post #2 answered the question, but this might be interesting - Regular or Extra Crispy.
If by “smallest possible” you mean theoretically possible instead of practically possible, in theory you can make very small nuclear weapons using californium; before people realized just how impractical it is to make it in significant amounts there was speculation about nuclear bullets using californium for the warheads.
More grist for the mill. The nuclear weapon archive is a useful starting point for many questions on the design and effects of these weapons. I hope the following relevant quote from it is small enough to fall under fair use:
It’s more of a bastardized fusion weapon that fuses tritium, IIRC, with the intention of creating an intense burst of radiation, but very little yield from the fusion reactions.
In other words, the fission trigger works as usual, but the fusion stage is tritium instead of lithium deuteride, which changes the characteristics of the reaction dramatically.
Nuclear weapon design is a series of tradeoffs- are the designers aiming for minimum fissile content, minimum weapon size, or something else like minimum yield? Each approach is different- minimum size weapons are frequently not very efficient, and minimum fissile content weapons are by nature, efficient, but can be larger and heavier for the same yield vs. a less efficient warhead of the same yield.
10-20 tons is like other posters have said, near the minimum realistic yield for fission weapons using the normal HEU and plutonium.
The weapon was a boosted fission device - the plutonium pit includes a small amount of tritium for a low level of fusion that increases the number of neutrons, improving fission. This tritium needs refreshing, as tritium decay produces Helium-3 that will absorb neutrons. The terrorists kill the nuclear engineer (East German) who designed the bomb and who had withheld this bit of information in an effort to stay alive - he just hadn’t mentioned that an additional step needed to be taken before deployment.
Si
“King Of The Wild Frontier” indeed!:eek:
Thank you, theoretically possibleis just what I meant I am sorry I was not clearer.
What is the smallest explosion youcould get with californium.
It was supposed to be a 400kt device that fizzled with a yield of 11kt. 400kt seems awfully high for a boosted fission weapon.
The threshold between fizzle and shock should lie between the 1.2 t and 7.8 t of the Hamilton and Humboldt tests:
It was supposed to be a true three stage fission-fusion-fission H-bomb (and I thought the predicted yield was higher than 400kt). I remember in the book after the bomb goes off an American military scientist first on the scene takes a sample of fallout, puts it into an analyzing machine of some kind and says, *“Whoa! Look at that Tritium count! This was a three-stager!”
For those who haven’t read the book:
A key plot point after the bomb goes off is even though the reader is told the bomb fizzled (Clancy gives an awesome nanosecond-by-nanosecond description in the chapter Three Shakes) the US is still fooled into believing it was a larger detonation and therefore a Russian attack not a terrorists one. It’s finally figured out that the miscalculation was because when the enormous asphalt parking lot at the stadium was vaporized it made the yield look much larger to the satellites that first detect the detonation.
The disaster at Kyshtim/Chelyabinsk in the former Soviet Union was due to an explosion due to improperly cooled nuclear waste. It wasn’t a “fission explosion”, but it certainly was due to the heat generated by fission decay (although not a chain reaction). The explosion was estimated to be the equivalent of 70-100 tons of TNT.
The area ended up being dangerously radioactive, and still is (two other incidents also contributed to the radioactivity). Zhores Medvedev mentioned the situation in the 1970s, and was immediately accused of being an alarmist. But the incident, while well-known in Russia, was virtually unheard-of in the West. (The CIA knew about it, but the government clamped a lid down on disclosures, maybe not wanting to have people freaking out about nuclear power) So he put together a book, Nuclear Disaster in the Urals, in which he proved that some sort of event occurred there in 1957 from available news and journal reports.
There are some folks who say that we narrowly avoided a similar disaster at the storage facility in Hanford, Washington.
I doubt this case is germane to this question, since the explosion itself wasn’t nuclear in any sense. It was a chemical explosion caused by concentrated solvent, which happened to contain dissolved radioactive metals. The same solvents in the same concentrations, heated to the same temperature by any other means, would have exploded identically.
This case is more like a hypothetical “dirty bomb”: conventional explosive seeded with radioactive compounds to generate a plume of radioactive fallout dispersed by a normal chemical explosion.