Question

Why uranium is used over any other radioactive element in a nuclear reaction usually?

Answer 1

• Uranium has 92 protons and either 143 or 146 neutrons, for uranium-235 and uranium-238 respectively. Nuclei with that many protons are always unstable (in fact, any nuclei heavier than lead are always radioactive).

• The electrostatic repulsion is between all the protons. Each one is pushing against each other one.
• The force drops off with the square of the distance, but the nuclei is small enough that each proton pushes every other proton away. Neutrons are unaffected by the electrostatic force. So, why doesn't the nuclei push itself apart?

the very heavy nuclei will tend to move to a more stable configuration. They do this by becoming lighter. They do this by emitting an alpha particle (2 protons and 2 neutrons). They will do this repeatedly (interspersed with some beta minus decay to reduce the neutron to proton number) until it reaches lead.

U-235 is less stable than U-238 because it has an odd number of neutrons (nuclei are more stable when their nucleons can pair up). Thus it has a shorter half life.

Since enriched uranium has a higher concentration of U-235 than natural uranium, it is more radioactive.