Abstract
The fusion reactor represents the most difficult challenge of any energy system from the viewpoint of developing materials which will allow fusion to be realized as an economic, safe and environmentally acceptable energy source. Substantial progress has been made over the past decade towards an understanding of the effects of the fusion environment on the properties of alloys, in identifying alloy systems which have the greatest potential for development as useful structural alloys, and in formulating and testing a metallurgical approach for developing irradiation resistant alloys with acceptable chemical and mechanical properties. Results to date give confidence that the long term objective – materials that will allow fusion to be an economical, safe and environmentally acceptable energy source – can be achieved. The next experimental fusion reactor, which will be either the International Thermonuclear Experimental Reactor (ITER), the Fusion Experimental Reactor (FER) or the Next European Torus (NET), will be the first device in which the effects of irradiation on the properties of materials will be a critical and limiting factor. At present, fission reactors are the only source of neutrons for the investigation of neutron irradiation damage and the development of radiation resistant materials. Spectral tailoring experiments in mixed spectrum fission reactors in which the neutron spectrum is adjusted to control the balance of transmutation produced helium and atomic displacements provide the closest approximation of fusion irradiation damage that can presently be achieved. These experiments suggest that for ITER conditions the most significant irradiation effects are in the areas of irradiation creep, loss of fracture toughness and possibly irradiation assisted stress corrosion cracking. A major expansion of the experimental programme will be required to develop a database for supporting the engineering design of ITER.