After perusingthis wonderful site and getting my chuckles out of it, I am reminded of something that has puzzled me for years; namely, why do nuclear bombs use an explosive to bring the pieces of radioactive material together? I presume it is not enough simply to bring them into contact with one another. Do they need to be compressed due to having a low concentration of Plutonium or whatever? Are they designed that way on purpose as a safety mechanism?
RR
In a fission bomb you have to compress the two subcritical masses together in order for them to become supercritical and start the fission chain reaction. The supercritical mass must be a certain density in order to start the reaction, so an shooting one at the other with an explosive helps.
In a fusion bomb, you need to compress the light gasses that you’re fusing in order to set off the reaction. In a star, this happens because of gravity. In a thermonuclear bomb, a small fission device is used to create an implosive force which compresses the gas, causing a fusion reaction.
Not that I know anything about nuclear bombs, but I doubt they use TNT these days. They probably use plastic explosives which are a hell of a lot more stable and just a little bit less scary.
You can get a nuclear reaction just by bringing enough uranium (or plutonium) together without the need for explosives (a hydrogen bomb must have the nuclear trigger however). However, without the explosives compressing the mass you’ll get more of a fizzle than an explosion. Bombs are all about releasing a LOT of energy in a SHORT amount of time. By bringing the atoms closer together much more material gets a chance to fission (consider it like shooting a spitball at a tennis net versus a porch screen…a lot of the spitballs will pass through the tennis net without hitting it but they’ll all get caught on the porch screen).
There have been examples of a reaction occurring just by having enough nuclear material close together. During the Manhattan Project one of the scientists was killed by radiation poisoning when an accident brought two masses close together and more recently there was an accident in Japan at a nuclear facility where workers got too much stuff in the same place at the same time. Neither case resulted in an explosion but you will get a boatload of radiation that is mighty bad for any living thing nearby. Also, IIRC someone around here once linked to a place on earth where naturally occurring uranium is actually maintaining a low level reaction all by itself (I would search for it but just now the hamsters seem to be tired so I’ll try when the board is faster).
Whack-a-Mole, you’re thinking of the Oklo uranium deposits in Gabon, a country in equatorial Africa. It’s not still active… but there’s evidence of it having fried when there was enough uranium brought together. See this site.