What Is Critical Mass in a Nuclear Reaction?

When an atom breaks apart, it shoots a bunch of particles. These neutrons are like little bullets,. and theyre shooting out, and they have just the right interactions to mess up the neighbors. And so what you need is a critical mass. When those neutrons fly out of the fisoning atom, they need something to hit as well. You need enough fuel so to pack densely together in order to make it so that you can have a self sustaining reaction.