Fusion is a beautiful process, not only for physicists but also a potential energy source, as it has distinctive advantages over traditional methods of energy production:
The fuels are abundant, deuterium is found in seawater and tritium can be generated from lithium inside the reactor. Lithium is widely distributed on Earth, it can be found in rocks and Lithium salts are also extracted from the water of mineral springs.
The fuels are widely available and well spread-out on the globe, and as such pose little risk of geopolitical conflicts on a limited amount of fuel.
There is a low risk of harming natural resources in harvesting (and transporting) these fuels, compared to the search for oil, coal or even windmills and hydropower.
There are no CO2 or other harmfull atmospheric emissions from the fusion process, i.e. it does not contribute to greenhouses gases or global warming. The only emission consists of a puff of Helium, which in turn can be used by other factories, or to fill children's balloons.
Fusion does not create any long-lived radioactive nuclear waste (it produces no actinides).
The direct safety of the reactor is also very important. In a tokamak, and most fusion devices, there is only sufficient fuel present in the vacuum vessel to sustain a fusion-burn for a few seconds.
Fusion is not a chain reaction, so unlike fission, a ‘melt down’ is not possible. The total amount of fusion fuel in the vessel of ITER will be very small at any point in time. Upon any disruption or breakoff of the fuel supply, the plasma cools within seconds and dies like a flame.
We try to get as many fusion reactions as possible inside the reactor. This means that any deviation from the optimum plasma configuration almost inherently will lead to a decrease in temperature or density, and stop the fusion reaction.
The ITER tokamak is build in Cadarache in France, an area with only moderate seismic activity. ITER however is build with specially reinforced concrete, and will rest upon bearing pads, or pillars, that are designed to withstand earthquakes. Seismic sensors around the site monitor all seismic activity, however minor.
The substance tritium is a used as a fuel but mainly produced inside the plant in a closed circuit. This means the total amount of tritium present can be kept very low (a few kg). Tritium is a weak beta emitter, but the radiation does not penetrate our skin. It should not be inhaled however, since it is very toxic inside the body. Therefore there are strict safety measures for handling of tritium fuel inside the reactor. The techniques for the safe storage and handling of tritium (which also has applications in medicine) are well developed. ITER has been designed to protect against tritium release and against workers' exposure to radioactivity.
When highly energetic neutrons interact with the walls of the internal components and the plasma chamber, these materials become activated. In-vessel materials can as such become contaminated with small amounts of radioactive dust. This material is properly shielded however by multiple protective layers. All waste materials will be treated, packaged, and stored on site, and the half-life of most radioisotopes contained in this waste is lower than ten years.