Some of the most significant technical challenges in building a Tokamak fusion reactor are:
The first item is the only one developed by past fusion projects. While ITER will address some of the other issues, it will not go far enough to give confidence that construction of an actual fusion power plant can proceed without further R&D.
Additional Issues, related to reactor operations but connected to the engineering solution adopted are :
These issues are examined, in varying detail, below and on other pages of the site.
Plasma confinement and heating are issues which have been developed in numerous experimental devices build since the 1950s. With ITER, it can be hoped that the remaining problems with plasma confinement will be solved, in particular the "disruptions" where the plasma is lost. However, much is needed to go beyond ITER towards an actual reactor.
A nuclear fusion reactor is an immensely complicated machine with numerous different new and unique systems. The neutron flux emitted by the fusion reactions will be enormous, on a level never previously dealt with and it will require new materials to withstand the damage from the radiation. These new materials have two differing requirements, they must retain mechanical stability under the radiation and they must also avoid becoming radioactive. Although progress has been made over the decades of R&D in the field extensive testing in a realistic environment is still required and no design has as yet has been proven to be viable.
The engineering of certain components of the Tokamak are particularly exigent: the plasma facing first wall; divertor, Breeder Blanket and superconducting magnets.
To prove the feasibility of materials and engineering components, it seems essential to make tests in facilities which simulate a realistic environment of a fusion reactor. No such facility exists at present and the proposed projects are described here: Test Facilities needed for Materials and Breeder Systems .
Mainstream plans for fusion reactor use tritium as fuel but because of radioactive decay, tritium is very rare and possibly a "show-stopper". Only about 30kg of tritium exists in the oceans of the world with about another 10kg in world stock from production in fission reactors. A GW fusion reactor would consume about 50kg/year of tritium. Surprisingly, despite these facts, the availability of fuel is often presented by advocates as an advantage. This issue is explained on the page: Impossibility of Tritium Fuel Supply .
The superconducting Magnets are the basics of magnetic confinement in tokamaks. Although established technology, there are difficulties involved in their employment : Risks with Superconducting Magnets .
A further engineering challenge is to make the multiple systems reliable and available to generate electricity a large fraction of the time. Numerous factors will contribute to making a fusion power plant available to generate electricity a lot less than 100% of the time. Some details of this complicated system are described here: Breeder Blanket .
In fusion reactors using D-T as fuel, 80% of the energy generated leaves the hot plasma as a flux of 14 MeV neutrons. The "blanket" system has the dual function of energy extraction and tritium breeding.
As already stated, this website concentrates on the mainstream fusion approach with Tokamaks and D-T fuel. In the past couple of decades dozens of projects with alternatives approaches have appeared largely with private funding.
The motivations for these new projects seem byzantine and will not be addressed here in any detail. Each project seems to be based around a particular different idea from the mainstream approach but share many common problems in from the list above. Many use different fuel which in principle solve some of the problems but make the plasma confinement and heating problem much more difficult and maybe impossible. A number are different, smaller Tokamaks using room temperature superconductors, which would be a big improvement on ITER, if this new technologies can become mature.
The following references describe these approaches: