In an atomic bomb, is the chain reaction controlled?

Question

I read that nuclear fission causes a chain reaction of energy being released, but it didn't tell me what would happen if the chain reaction was not stopped, only that it was similar to an atomic bomb. Obviously, an atomic bomb does not explode forever, so what stops it?

Answer 1

The reaction stops when the reactants (fuel) are depleted or dispersed by the explosion.

Answer 2

It looks like in your question it's actually 2 questions, I'll try to answer them the best I can.

If in a fission reaction the reaction is uncontrolled like in a nuclear reactor, you would have a result like Chernobyl back in the mid '80's where the reactor melted down because of a malfunction in the shutdown sequence which caused the reaction to go out of control.

The reaction was stopped by the extinguishing of the reaction by dropping various chemicals on the reactor core. It didn't explode like a nuclear warhead because the uranium used in commercial nuclear power reactors isn't pure enough to cause that kind of a reaction.

It's usually about 35% pure or somewhere around that, it's what's known as being fuel grade. Now for nukes it's got to be about 98-99%+ pure which is known as weapons grade uranium.

Now a nuclear bomb is quite different, I'm no nuclear physicist so I can't give you the nuts and bolts of how a nuclear bomb works.

However the reaction doesn't go on forever, if I remember the basics it's an implosion reaction. Where high explosive shaped charges are designed to direct their explosive energy into the "pit" of uranium that's supposed to create the nuclear blast.

The explosive energy causes the uncontrolled reaction if the fission within the "pit" to happen at an incredibly high speed.

Most fission reactions accelerate over time, this causes it to happen almost instantaneously, which would account for the fuel being used up so the explosion doesn't go on forever.

This is the best explanation I could think of, I hope it helps you out.

Answer 3

The neutrons released to detonate the bomb start a very rapid and violent chain reaction releasing a great deal of heat and energy. As a result of the atomic blast , the materials present at the start of the reaction are different materials and too far apart for the nuclear reaction to continue. However, many radioactive particles and materials are released that have long term effects on living things, such as causing forms of cancer.

Answer 4

The reaction stops when the fissionable material is all fissioned. And yes it is an uncontrolled chain reaction. Such is the nature of a bomb.

Answer 5

It is just such a concentrated amount of energy. When the particles reach a certain distance eventually they spread out so thin that they are undetectable

Answer 6

The core is blown apart and is no longer a critical mass.

Answer 7

It loses momentum.