Basic scientific principle behind a nuclear reactor is

The basic scientific principle behind a nuclear reactor is controlled nuclear fission. Nuclear fission is a physical process where the nucleus of a heavy atom, such as uranium-235, splits into smaller nuclei, releasing a significant amount of energy and additional neutrons [1]. In a nuclear reactor, this process occurs as a self-sustaining chain reaction. To ensure safety and a steady power output, the rate of fission must be rigorously managed using control rods made of neutron-absorbing materials like cadmium, which capture excess neutrons. This distinguishes reactors from nuclear weapons, which rely on uncontrolled chain reactions that release energy exponentially and instantaneously. While nuclear fusion is the process powering stars, it currently remains in the experimental research phase for electricity generation because it requires extremely high temperatures and is difficult to control.

Sources

1. [1] https://www.energy.gov/ne/articles/nuclear-101-how-does-nuclear-reactor-work