Neutron-induced fission

The three sections in this simulation allow students to (a) see how neutron-induced fission occurs in a Uranium-235 nucleus, (b) see how a chain reaction can be established when molecules of U-235 are located near each other, and (c) see how fuel rods containing U-235 in a nuclear reactor can be arranged so as to sustain a nuclear fission chain reaction. Students are asked to compare and contrast nuclear fission and fusion. To do so, they must have an accurate model on the atomic level for both processes. This simulation focuses on fission, and clearly depicts what happens to a U-235 nucleus during neutron-induced nuclear fission. The first section of the simulation has a superimposed energy graph that depicts the U-235 nucleus in a potential energy u201cwellu201d prior to absorbing a neutron. Acquiring the additional neutron produces U-236, which is less stable than U-236 and thus undergoes fission. The superimposed graph allows the student to see that the destabilization of the nucleus results in the increase in its energy content, which is why fission of U-235 occurs primarily only after neutron absorption. The other two sections of the simulation allow students to experiment with the chain reactions that make nuclear fission useful and, if not controlled, dangerous.