What is the principle of a nuclear reactor?

Answer 1

how the nuclear reactor can work?

A nuclear reactor is a system which generates a nuclear fission reaction. A nuclear reaction is a self-sustaining reaction where the output of one stage is the input of the next stage. Therefore, if there is enough fuel, the reaction will continue indefinitely.

The most common type of fission reaction is a Uranium 236 reaction. Nuclear fission involves splitting an atom into smaller atom(s). In a U236 reaction, Uranium 235 is the fuel. A neutron is propelled, which strikes the nucleus of a Uranium 235 atom, creating a U236 atom. U236 is highly unstable, and undergoes radioactive decay. This means the U235 atom turns into a Krypton atom, and a Barium atom, plus 2 extra neutrons and some energy. This energy is generally heat, and is absorbed by nearby water, which boils and turns a turbine.

The two neutrons continue the reaction by hitting another U235 atom (each).

There are other types of nuclear reactions as well, but the principle is the same. The output is generally atoms of different Atomic Mass, energy, and some other byproduct which will continue the reaction (e.g. an alpha particle - a Helium nucleus, or a neutron). In nuclear fission, the atom byproducts have a lower atomic mass.

In nuclear fusion, the atom byproducts have a higher atomic mass (since multiple atoms are fused together). Nuclear fusion is the basic power plant in the core of the sun (combining Hydrogen atoms into Helium, or Helium into Carbon, etc.). The byproduct here is the energy that we see as light.

Slow neutron fission chain reaction.