Immense Challenges for Nuclear Fusion Reactors
This page introduces the immense challenges to make an economy based on commercial nuclear fusion. This website focuses on mainstream fusion with tokamak reactors but the alternative technologies have similar challenges.
The most significant challenges for a tokamak fusion power plant are:
- Plasma confinement
- Engineering feasibility and reactor availability
- Tritium fuel cycle
- Cost
- Radioactive waste
- Safety
These multifaceted issues are examined in the pages indicated below.
Plasma confinement
Plasma confinement has been the main goal of numerous experimental devices built since the 1950s. Problems with plasma stability remain, and the main task of the upcoming ITER project is to solve them. Nevertheless, "disruptions", where the plasma is lost in an uncontrolled way, must be reduced to a very low level for operation of a commercial reactor. This is discussed on the page Tokamak Fusion Reactors.
Engineering feasibility and reactor availability
A nuclear fusion power plant is an immensely complicated machine with multiple new and unique auxiliary systems. These systems include:
- Plasma containment vacuum vessel
- Cryostat and pumping systems
- Heat extraction and power generation plant
- Superconducting magnets and power supplies
- Plasma heating systems
- Tritium purification and recycling systems
- Remote handling maintenance apparatus
- Radioactive component storage facilities
The neutron flux emitted by the fusion reactions will be enormous, on a level never previously dealt with, and new materials are required to withstand the effects of the radiation. The neutrons emitted from the reactions in the plasma have two different effects on materials: radiation damage and activation of radioactivity. Any new material must be designed to avoid both these problems. Although progress has been made in developing suitable materials through decades of research, extensive testing in a realistic environment is still required to qualify them. Even so, the tokamak components closest to the plasma will need to be frequently replaced.
A paramount requirement of any design is feasibility of manufacture and construction. A fusion reactor which would be competitive with recently constructed fission reactor would need to be very large. The page, Pharaonic Size and Byzantine Complexity, argues that this is not realistic. Estimates of the reactor reliability and availability are presented in the page, Maintenance, Breakdowns and Availability.
Tritium fuel cycle
Mainstream plans for fusion reactors use tritium as fuel, but tritium is very rare and the supply is possibly a "show-stopper". Only about 30 kg of tritium exists in the oceans of the world with about another 25 kg in world stocks from production in fission reactors. A GigaWatt fusion reactor would consume about 50 kg per year of tritium. This issue is explained in the page: Lack of Tritium Fuel Supply.
Costs
Ultimately, the cost of electricity generated by fusion, relative to other possible clean generation technologies, will decide if fusion enters into commercial exploitation. At present, the cost of fusion is not well evaluated but a discussion of this essential issue, giving some estimates and guesses is given in the page: Reactor Costs, Fusion compared to Fission.
Radioactive waste
Radioactive waste is a common "cause celebre" and used as a frequent objection to the use and expansion of nuclear fission power. Fusion propaganda exploits this cause celebre, claiming that fusion produces little waste, and so should replace fission. In reality, the waste from fusion is short-lived, but produced in large volumes. Fission waste is, in part, long-lived, however these long-lived isotopes are produced in small volumes. This is covered in the page: Radioactive Waste.
Safety
Another claim of fusion propaganda is that fusion is intrinsically safe while fission is intrinsically unsafe. The reality is not simple and a measure of the real safety risks for fusion reactors can be judged from the need to construct three-metre-thick containment structures around them. An extensive discussion on the relative safety risks for fusion and fission, together with some specific examples of risks for fusion power plants, is giving in the page, Safety of fusion compared to fission.