Nuclear fusion is a process in which light atoms merge creating heavier elements and producing large amounts of energy. Nuclear fusion powers the stars mostly in a process where hydrogen atoms change into helium. This process requires large energies because the nuclei are positively charged and repel each other. Therefore temperatures of millions of degrees are required for the fusion to work.
There are several ways to recreate these conditions in a fusion plant. One of them is so called tokamak. This is a spheroidal (donut like) shape in which light ions are accelerated to great velocities and their paths curved around the tokamak with strong magnetic fields. In order to provide enough energy different heating techinques are used. In Fusion game we will use radio heating and neutral beam injection. Also hydrogen-hydrogen reaction is hard to achieve, it's easier to do a fusion between deuterium and tritium. Deuterium has a proton and a neutron while tritium has a proton and two neutrons. When both collide they form a helium atom with two protons and two neutrons, while the remaining neutron is ejected carrying a lot of energy. These neutrons will hit the inner shielding of the tokamak heating it up and this is how we generate thermal energy.
Tokamak is fed by ion injectors which inject deuterium and tritium at the correct proportion 2D/3T. However it's usually hard to eject the helium which is a waste therefore tokamaks are often designed to work in a few minute cycles. After each fusion cycle the reaction stops and everything is ejected outside and refilled again. In order not to lose the precious remains of the fuel separation columns are used to recycle deuterium and tritium back into the storage tanks.
Thermal energy has to be taken out from the tokamak by cooling it. This is achieved by a helium circuit which transfers out the thermal energy. In the game design a secondary circuit consists of molten salt, although in real life also other designs are proposed. The idea of having a molten salt circuit is the ability to store the termal energy. Molten salt has a very high thermal capacity so if we have a big enough tank we can store the hot salt there for later use. This kind of design exists because tokamak tends to work in a cycles and the power network prefers to receive a constant (base) load of energy. We can therefore store energy during fusion cycles and use it during cleanup process.
The last circuit in each thermal plant consists of light water. Molten salt will heat up the water and let it boil in the steam generator. Steam will then power the turbine generating electricity and later be condensed back into water and reused. Turbine control are similar to our other experiences of RBWR and RPWR games.
Many devices in the plant require use of very low temperatures (as low as 5 kelvins). These devices are placed in a cryostat which is a containment held under a strong vacuum. Cryostat is cooled in two stages by gaseus and liquid helium.
Generation of very strong magnetic fields required for the tokamak is possible only thanks to superconductivity. When superconductor is cooled well enough (in the game below 5 kelvins) the circuits show no resistance. Therefore they can be charged to enormous amounts of electrical current without generating any heat or any energy loses. In the game the coils usage is simplified and gameplay oriented although it aims to simulate the process of charging or discharging them and model how it affects the matter in the tokamak.