Fusion Fuel Basics
In atomic fusion atomic nuclei are joined together to form a new one. This process releases more energy than it consumes.
Commonly, the nuclear fuel being used for this are two variants, also called isotopes, of hydrogen. One is deuterium, denoted by 2H, and the other tritium, denoted by 3H.
While the atoms are electrically neutral, the atomic nuclei are charged positively. This is because they consist of one proton which are positively charged, and one or two neutrons, for deuterium and tritium respectively, which carry no electric charge. Since all the nuclei carry the same, positive charge they will repel each other and the closer they are brought together, the stronger the repulsive force gets.
To overcome this repulsion and make them join, the atoms are heated to tens of millions of degrees (Kelvin). When this is done the atoms themselves no longer are electrically neutral, and become charged. They form a plasma. In this state the repelling force can be overcome and the nuclei can be made to join together to form a Helium nucleus and release energy in the process.
Fusion Reactor Basics
The heated plasma is difficult to handle. One way to control it is to contain it in a energy generation is the tokamak design. This design is also being used by the ITER project, which is an international cooperation of the EU, China, India, Japan and the US.
In the tokamak design, the plasma is contained in toroidal fields, as shown in figure 2 below. It is thought that this design will release about ten times more energy than it consumes.
According to ITER on its website the advantages of nuclear fusion are the following:
First of all, fusion is an almost limitless fuel supply. The basic fuels are distributed widely around the globe. Deuterium is abundant and can be extracted easily from sea water. Lithium, from which tritium can be produced, is a readily available light metal in the Earth´s crust.
Fusion produces no greenhouse gas emissions. Fusion power plants will not generate gases such as carbon dioxide that cause global warming and climate change, nor other gases that have damaging effects on the environment.
Fusion is suitable for the large-scale electricity production required for the increasing energy needs of large cities. A single fusion power station could generate electricity for two million households.
Waste from fusion will not be a long-term burden on future generations. Only metal parts close to the fusion plasma will become radioactive. Any radioactive waste generated will be small in volume and the radioactivity will decay over several decades with the possibility of reuse after about 100 years.
No transport of radioactive materials is required in the day-to-day operation of a fusion power station, as the intermediate fuel tritium is produced and consumed within the power plant.
The fusion reaction is inherently safe. Only about two grams of fuel is present in the plasma vessel, enough for a few seconds of “burn”. As fusion is not a chain reaction, the reaction can never run out of hand.
Much about the safe operation of fusion power plants will be learned from the safe operation of ITER. There will be significant changes in materials and cooling for the power reactor, and overall power densities will be somewhat higher. Outline reactor designs have been made to analyse the extent of any problems. These show that some of the problems faced by ITER will get simpler, and a few new accident scenarios will be introduced. However, ITER is by and large prototypical for determining the safety features of magnetic fusion.