Thermonuclear fusion powers the stars and produces 10 times more energy than fission. Mastering it in Earth conditions would provide an endless source of energy, but many technological challenges have yet to be solved.

The tokamak uses a toroidal magnetic cage to isolate hot plasma from vessel walls. Thermonuclear fusion can be ignited inside after reaching suitable conditions. More than 50 tokamaks are involved in fusion research today.

The idea of a stellarator is based on the premise that plasma can be held in the reaction space by means of a special helically wound magnetic field that is generated exclusively by magnetic coils of various shapes.

Ionising radiation is produced by the radioactive decay of unstable atomic nuclei called radioisotopes. It is everywhere around us, has different abilities to penetrate matter and various properties that we can exploit.

Subatomic particles can interact with atomic nuclei when they come within range of strong nuclear forces. Neutrons, protons or other particles can bounce off, excite the atomic nucleus, enter the nucleus or cause fission.

The nuclear fuel cycle begins with mining and processing the ore, enriching to the required concentration of fissile isotopes and producing fuel assemblies. Spent fuel is temporarily or permanently stored or reprocessed.

Nuclear power plant generates energy by fission of atomic nuclei in the reactor core. The reaction is controlled by a moderator and absorber. The heat is transferred to a steam turbine which converts it into electricity.

The first nuclear reactor was built by Enrico Fermi from graphite and uranium, and in 1942, he started the first controlled fission reaction. In 1951, the electricity from the first nuclear power plant lit four light bulbs.

Most common types of nuclear reactors use ordinary water as a moderator and coolant. These are Pressurized Water Reactor that uses water under high pressure and Boiling Water Reactor in which water boils in the reactor vessel.

People have always used renewable energy sources, such as burning biomass to heat food, wind to propel ships, or water to power mills. Today, renewables are important for the transition to clean and sustainable energy.

Renewable sources are clean, safe and easy to operate, but they have also low output density and a strong dependence on weather, location and season, which places certain demands on the electricity production from them.