Before revision: File:File:Example.jpg File:File:Example.jpg File:File:Example.jpg In nuclear engineering, neutrons which have not yet undergone a collision are termed the 1st generation, those which have undergone a single collision the 2nd generation, those which have undergone two collisions the 3rd generation, and so on.
After revision:  In nuclear engineering, neutrons which have not yet undergone a collision are termed the 1st generation, those which have undergone a single collision the 2nd generation, those which have undergone two collisions the 3rd generation, and so on.