Years later, remembering how enjoyable the treat had been, Epperson went into business producing popsicles.
Of these three naturally occurring isotopes of uranium, U-238 is by far the most common, while U-235 is the most capable of undergoing nuclear fission. 7A More than 99% of all naturally occurring uranium is U-238, while U-234 and U-235 each make up less than 1%. 7B Nuclear fission can occur when a U-235 nucleus is struck by a neutron, and the nucleus splits, releasing energy and releasing two or more neutrons. 7C However, nuclear fission rarely involves a U-238 or a U-234 nucleus because it is unusual for either of these nuclei to break apart when struck by a neutron. 7D