New designs of plant are being proposed to cover a wide size range of power outputs. For example, large evolutionary plants with outputs of the order of 1500 MWs are being developed utilising proven active engineered systems. Medium to large-scale plants are being considered which take account of more inherently safe features such as passive safety systems. These passive systems are being scaled up for higher power output plants, in which previously the safety functions could only be accomplished by active systems. Small-scale plants are being designed which encompass novel fuel technologies, etc.

All these designs have common objectives, e. g. high availability, user friendly man — machine interface, competitive economics, and compliance with internationally recognised safety targets (Juhn, 1999).