What we miss in order to be able to design and build a commercially viable fusion reactor

The paper considers in a critical way the different areas in which work is required to provide sufficient information in view of designing a reliable and attractive fusion reactor. Four main areas of activity are considered: physics, technology, engineering, safety. In physics the trend is positive towards a better understanding of suitable plasma regimes to be confirmed through further experimentation on the operating machines. Engineering has already proven itself by the design and construction of a number of experimental machines. In addition a large data base obtained from design and operation of fission reactors is available. Safety is reaching very satisfactory results in the analysis of the impact of fusion on man and the environment. Where it is still a large unsolved problem is concerning materials capable of standing the harsh fusion environment for an adequate number of years. An intense neutron source is needed in order to allow the necessary developments