This website has given many reasons why the mainstream approach towards commercial nuclear fusion reactors (Tokamaks with Deuterium-Tritium fuel) will be extremely difficult to achieve. This page summarizes, characterizing some problems as "Show-Stoppers".

No tritium fuel

Tritium fuel is rare in nature. Essentially all supplies of tritium come from fission reactors and is only available in limited quantities at exceedingly high prices. Any commercial fusion reactor must breed its own supply of tritium, once in production, in order to be viable. Existing studies of tritium breeding indicate the chance of success in this is very low. Even if this is possible, a significant amount of tritium will be needed for reactor start up and this will not exist.

No suitable materials

Neutron radiation damage to materials, even after decades of R&D, means major components must be frequently changed. For some like limiters, divertor and breeder blanket replacement schedules are included in the design specifications at great cost in finance and available reactor time. For some situations it is not clear that current designs will be able to meet the specification. Further, there are other parts of the reactor, such as the vacuum vessel which it is not planned to replace but nevertheless will have a finite lifetime which is as yet uncertain.

The whole issue of radioactive waste depends on impurities in the delivered materials. Past R&D has lead to solutions which can give acceptable radiation levels for pure metals and alloys but the impurities can completely change that. Further R&D on specific materials will not change this, only R&D on industrial purification processes which will inevitably be very expensive because of the 1000s of tonnes of material required.

Impossible scale for competitive fusion power plant

Fission reactors planned, have electricity outputs up to 1.8 GW. To compete in the same market, fusion plants would need to have similar power, however, the prototype DEMO reactors being planned only have 0.5 GW output. Even at this scale they would be 1.5 bigger than the enormous ITER project which seems to be already at the limit of size feasible logistics can handle. Ever making a 1.8 GW fusion power plant seems clearly impossible.

Why has it not stopped already?

The three show-stoppers discussed above, convince many people but obviously do not convince everyone because the show is still going-on. Die-hard fusion advocates argue that nothing is impossible; perhaps after 40 years of R&D on tritium breeding new idea will appear; perhaps further research will find better materials; perhaps bigger roads and cranes can be built. 

Perhaps these arguments are not effective because they are too technical and impossible for the average member of the general public or the average politician to grasp. The propaganda "Unlimited Energy" wins.

Below is further set of show-stopper reasons which are conditional on the occurrence of events which would clearly be understood by the public and politicians.

ITER failure

The international ITER project is putting all mainstream fusion eggs in one huge complicated basket. If ITER fails it will be noticed by politicians everywhere and a restart of a similar fusion project will be impossible. There are many paths by which ITER could fail:

  • Plasma Physics. The primary goal of ITER is to finally solve the problems with plasma confinement and disruptions. If it fails here, it is unlikely there will ever be a new biggest project with the same role.
  • Technical Fault. Any number of engineering issues could lead to project failure. One risky decision has been taken to skip power tests of superconducting magnets, possibly other technical gambles have been made. The ITER tokamak design means a repair of the magnets coils will be impossible without several years of work and corresponding expense. 
  • Political collapse. The multinational structure of ITER is slowly being eroded for numerous reasons. The current funding arrangement ends in 2035 and some significant extension will be needed. This might not happen.
  • Nuclear Regulatory Rejection. ITER is licensed by the French nuclear safety authority (ASN). Agreement by ASN must be given at certain stages of ITER construction. Between, January-July 2022 ITER construction has been stopped because of objections of ASN. The progress of ITER towards completion depends on ASN approval and safety concerns might halt ITER.

Radioactivity incident

Fusion reactors have high levels of short-term radioactivity which could be released to the atmosphere or cause harm to personnel internal to the site. If there ever is a nuclear fusion accident, It is likely, that the "intrinsically safe" and  "no radioactivity" propaganda will be remembered. 

The complex remote maintenance operations necessary to exchange the radiation damaged components are clearly a major risk, where a breakdown might require either a dangerous human or decades of machine stop to allow radioactive decay of hot regions.

Confidence in nuclear fission has been badly damaged for decades by the early nuclear accidents, a new fusion industry would certainly suffer the same fate or worse.

Final argument

The next page, Why Bother with Fusion rather than Fission?  gives the culminating argument.