While other elements can be used for fission, Uranium is the only one found naturally in significant quantities that is also fissile, meaning its atoms can be split by neutrons.
It's important to note that:
* Thorium is another naturally occurring element that can undergo fission, but it's not fissile. It needs to be converted into a fissile isotope (like Uranium-233) through a process called neutron capture and beta decay.
* Plutonium is fissile but is not naturally occurring. It's produced through neutron capture in Uranium-238.
Therefore, Uranium remains the only naturally occurring element used for nuclear fission.
