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Non-nuclear energy

Safety and environment

Fission and radiation protection
Fusion
   

The JET facility © Image: JET/UKAEA

The JET facility
© Image: JET/UKAEA

As a result of the need to ensure that fusion is as safe as possible and is a low environmental impact method of generating baseload electricity, the European Safety and Environmental Assessment of Fusion Power (SEAFP) team was set up. The main participants in SEAFP were the NET (Next Experimental Torus, the ITER team at the time) team, UKAEA, other European fusion laboratories, and a grouping of major European industrial companies.

The work embraced the conceptual design of fusion power stations and safety and environmental assessments of those designs. Detailed work was carried out mainly on the identification and modelling of conceivable accident sequences, the potential hazards of normal operation, waste management and the long-term availability of materials.

The major conclusions reached by the SEAFP team were that fusion has very good inherent safety qualities, with no chain reactions or production of 'actinides' (‘radioactive’ elements with long half-lives). The worst possible accident originating in a fusion power station could not breach the confinement barriers, and any releases could not approach levels at which evacuation of the local community would be considered.

The radio-toxicity of a fusion power station's waste materials will decay very rapidly. After less than 100 years the residual activity will be equal to the radio-toxicity of the waste from a coal-fired power station. Thus, fusion wastes present no accumulating or long-term burden on future generations. They would not need guaranteed isolation from the environment for very long timespans.

In addition to these favourable results, fusion does not produce any climate-changing or atmospheric pollutants. The generation of fusion power – as with fission power – will not create greenhouse gases. In addition, it will not produce other environmentally harmful pollutants or long-lasting radioactive waste.

Its fuel consumption will be extremely low. To generate 7 billion kilowatt-hour a 1 000-megawatt electric fusion power plant would consume around 100 kg of deuterium and three tonnes of lithium in a year. To produce the same amount of electricity, a coal-fired power plant would need around 1.5 million tonnes of coal.

The potential role of fusion in satisfying the energy needs of the 21st century, its costs, benefits and public acceptability are also important areas of study. The impact of safety and environmental constraints on the economic aspects of a fusion power plant also represents a significant element of the programme.

Work on the Safety and Environmental Assessment of Fusion Power Long-term (SEAL) has continued the work of SEAFP including:

  • investigations into irradiated beryllium (a possible coating of the plasma facing components)
  • calculations of activation and source terms
  • personal safety
  • hydrogen (tritium) interaction with plasma facing components
  • breeder blanket safety analysis
  • analysis of radioactivity confinement
  • design against external hazards
  • assessment of plant availability and maintenance
  • waste management and disposal.

Work has also continued on SEAFP-2 and SEAFP-99 to extend these in-depth studies of the safety of a commercial fusion power plant, involving the calculation of energy inventories in the plant by analysing multiple failure sequences and maximum radioactive doses to exposed individuals. The work has also given consideration to improved containment concepts for the fusion reactor core, the production of activated materials during the lifetime of a fusion power plant and their possible reduction through recycling and material optimisation.

Within SEAFP-99, a long-term safety project was launched focusing on the assessment of occupational health and safety issues, and the influence on power plant availability and evaluation of safety and environment issues on advanced breeder blanket concepts.

Conclusions of the Safety and environmental impact of fusion (SEIF)

The study – Safety and environmental impact of fusion (SEIF) – integrated and extended all the previous work and concluded that, for any future fusion power station:

  • any power excursion will be self-limited to low levels by the inherent processes in the plasma
  • the small fuel inventory in the plasma chamber at any time will mean quick shutdown
  • power densities will be moderate during normal operation and very small after termination of the fusion burn
  • activated waste produced by the operation of a power plant will not be a burden for future generations.

In addition the radioactive fuel component tritium is both produced and consumed on site; therefore, there are no issues regarding transporting radioactive fuel, and the system has no weapons proliferation concerns.

Fusion offers the prospect of operational safety, environmental compatibility and sustainability providing a CO2-free energy source to supply future baseload electricity. A summary of the report can be found on the EFDA website.

Inherent safety for ITER and beyond

The key aspects of ITER safety are effluents and emissions from normal operation, including planned maintenance activities; occupational safety for workers at the facility; radioactive materials and wastes generated during operation and from later decommissioning; and potential incidents and accidents.

The Generic site safety report (GSSR) documents the implementation of a generic safety approach including the safety aspects of the design, and the assessments of effluents, occupational safety, waste, and accidents. The analyses and assessments in the report offer a well-developed technical basis for regulatory applications and licensing of ITER in all of the potential host countries.

The results of the GSSR indicate that effluents during normal operation are estimated to be less than 1% of natural background radiation levels. Occupational exposure of workers is estimated to be less than the guidelines set for the next-generation nuclear (fission) power plants. The majority of the radioactive materials from operation and decommissioning can be released from regulatory control in reasonable timescales. It is estimated that 60% of the material would be below IAEA clearance levels after 30 years, growing to 80% after 100 years.

Radioactive doses from any postulated accidents are estimated to lead to doses to the general population at worst comparable with the average annual natural background for a generic site. No single component failure will lead to very large consequences and no single event can simultaneously damage the multiple confinement barriers provided in the ITER design.

The GSSR assessments showed that ITER can be constructed and operated safely and without significant environmental impacts.

What makes fusion so safe?

A fusion reactor is like a gas burner. All the fuel injected is ‘burnt’ in the fusion reactor. The density of fuel in the reactor chamber is very low (around 1 gram of deuterium/tritium fuel in 1 000 m3). Any malfunction will cool the plasma and stop the reaction, thereby making a runaway situation impossible.

Regarding fuels, deuterium, lithium and the helium produced in the reactions are not radioactive. Tritium is radioactive but has a short half-life – 12.6 years. However, this tritium will be produced and used inside the fusion reactor. Therefore, no transport of radioactive fuels would be needed for the day-to-day running of a fusion power plant. Even in the worst-case scenarios, there would be no need to evacuate neighbouring populations.

The European ITER Site Study Group

The European ITER Site Study Group (EISS) was formed to carry out the necessary safety and other analyses necessary for the preparation of the European application to host ITER. The EISS group was made up of members of European associations, European Commission representatives, the Garching support group and the central ITER group. The EISS assessed essential requirements such as space, electricity supply, transport access and the necessary legislative framework and issues like seismic constraints and the industrial, social and cultural environment.

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