Animations

The animations can be watched online or downloaded in .swf format. Information on how to insert the animations into powerpoint presentation can be found here and here.

The atom

All matter consists of atoms, which are composed of a nucleus, with negatively charged electrons circling around it. The nucleus consists of protons, which have a positive charge, and neutrons, which have no charge.

 Download swf File (2 KB)  [The atom]

Hydrogen - Deuterium - Tritium

Deuterium and tritium are isotopes of hydrogen. This means that they differ from hydrogen only in the amount of neutrons in their nuclei. Deuterium has one extra neutron, and tritium has two.

 Download swf File (2 KB)  [Hydrogen - Deuterium - Tritium]

Fission

Fission is a nuclear process in which a heavy atom is split into smaller parts by a neutron. Energy and additional neutrons are released.

 Download swf File (2 KB)  [Fission]

Tritium

Tritium has a half-life of 12.3 years, which means that after that period, half of the original tritium has disappeared. When it disintegrates, it emits an electron (beta radiation) of very low energy.

 Download swf File (2 KB)  [Tritium]

Fusion

Fusion is a nuclear process in which two light atoms fuse together to make a larger one. During this process, a lot of energy is released, which comes from the strong forces acting in the nucleus. In the animation, a deuterium nucleus (an isotope of hydrogen), fuses together with a tritium nucleus (another isotope of hydrogen) to form a helium nucleus, and a single neutron.

 Download swf File (2 KB)  [Fusion]

Breeding Tritium

Inside a fusion reactor, tritium is produced from lithium, a light metal. The neutrons released in the fusion process turn the lithium into helium and tritium.

 Download swf File (2 KB)  [Breeding Tritium]

Nuclei repel each other

The protons in a nucleus have a positive charge. That means that when two nuclei come close together, the electrical forces try to push them away from each other.

 Download swf File (2 KB)  [Nuclei repel each other]

Nuclei need a high temperature to fuse

If two nuclei come very close together the strong forces can start acting and the two nuclei are suddenly attracted to each other. To get the nuclei to come close enough together and prevail over the electrical repulsive forces, they need to collide with a very high speed. This means that the particles need to have a very high temperature: in a fusion reactor, the temperature is 150 million degrees. At that temperature, hydrogen nuclei move with a thousand kilometres per second.

 Download swf File (3 KB)  [Nuclei need a high temperature to fuse]

The states of matter

In an ice cube, the atoms are arranged regularly, and have a fixed position constituting a solid material. When it is heated, it melts and becomes fluid, and the molecules can shift freely. At still higher temperatures, the water evaporates and forms a gas, called steam. If we continue heating, the molecules of water fall apart into oxygen and hydrogen atoms. And at still higher temperatures, the atoms themselves fall apart into free nuclei and free electrons. This state is called plasma.

 Download swf File (2 KB)  [The states of matter]

Magnetic fields can control a plasma

In a plasma, all particles move in all directions. If a magnetic field is present, the charged particles in the plasma will follow the field lines, as if guided by a rail. In this way, we can keep the plasma away from the walls.

 Download swf File (2 KB)  [Magnetic fields can control a plasma]

Magnetic field of a tokamak

If the toroidal coils are active, a magnetic field is generated that follows the direction of the torus. The particles follow these field lines, but there is a subtle effect that causes the electrons to drift upwards, and the nuclei to drift downward. Through this effect, the confinement of the plasma is lost.
If a current flows through the plasma, the current generates a magnetic field which winds around the torus. Although the particles are confined by these magnetic field lines, the plasma as a whole is unstable, and it quickly starts to wobble. After a short while, the particles escape.
If both the plasma current and the toroidal coils are active, the two fields that are generated add up to a field that winds around the torus in a helical way. Additionally, equilibrium is reached by adding a vertical field generated by poloidal field coils. Separation of particles is not possible any more, as the top section of the plasma is now mixed with the bottom section. This provides very effective confinement.

 Download swf File (2 KB)  [Magnetic field of a tokamak]

Components of a fusion power plant

A fusion power plant consists of many different parts: the plasma, the fuel system, the magnets, the blanket, the heat exchangers, the steam turbine and many more.

 Download swf File (2 KB)  [Components of a fusion power plant]

Heating the plasma

To reach the extremely high temperature of 100 million degrees, different methods of heating are used: an electrical current through the plasma, beams of high-energy neutral particles (called neutral beams), and microwave radiation. In practice all techniques are used together, as they also serve as a way to influence the behaviour of the plasma.

 Download swf File (2 KB)  [Heating the plasma]

Inertial fusion

In inertial fusion a small pellet of frozen deuterium-tritium mixture is illuminated from all sides by very powerful lasers or ion pulses. The outer layer of the pellet becomes very hot and blasts away from the pellet. This causes the inner part of the pellet to be compressed very quickly with a huge pressure. The compression causes the temperature and density of the remainder of the pellet to increase so much that the deuterium and tritium fuse together.

 Download swf File (2 KB)  [Inertial fusion]