Mention the use of controlled nuclear fission. Mention the use of uncontrolled nuclear fission.

(N/A) $1$. Controlled nuclear fission: It is used in nuclear reactors to generate electricity. In this process,the chain reaction is regulated using control rods (like cadmium or boron) to absorb excess neutrons,ensuring a steady release of energy.
$2$. Uncontrolled nuclear fission: It is the principle behind the working of nuclear weapons (e.g.,atomic bombs). In this process,the chain reaction is allowed to proceed without any regulation,leading to a rapid and massive release of energy in a very short time.