Imagine that you are in the very first stages of trying to figure out how to bui
ID: 1902472 • Letter: I
Question
Imagine that you are in the very first stages of trying to figure out how to build a nuclear power reactor or a nuclear weapon using fission. The first step you would consider is what kind of nucleus could live for a reasonable length of time so that you could keep it around, but would also be able to decay by some process that would give off lots of energy.1. Explain why you could be pretty sure that any suitable isotope would have a lot of protons and a lot of neutrons.
2. In induced fission a neutron is used to induce fission. Why is a neutron used to induce fission instead of a proton?
Explanation / Answer
1)First of all, it is reasonable to assume that the nuclei would contain a lot of protons, since the more protons that are in a nucleus, the more they repel on another and the more electrostatic potential energy is stored up in them and the more energy they would release upon fissioning. We also want the nuclei to be stable for a reasonable length of time before decaying. Adding additional neutrons to the nucleus will reduce the proton-proton repulsion by increasing the size of the nucleus without adding any extra positive charge, so putting some separation between the protons that are repelling each other. Nuclei with large numbers of protons will therefore have a reasonably long lifetime due to the large number of the neutrons, and will also give off lots of energy due to the large number of protons 2)Neutrons are electrically neutral, which means that they will not experience an electrostatic force as they approach a positively charged nucleus. Protons, on the other hand, will experience a repulsive electrostatic force due to the presence of other protons in the nucleus. Since the neutrons are electrically neutral, it is much easier to collide them with nuclei to induce fission than it is to use protons to induce fission.