Abstract
With the worldwide development of fusion power focusing on the design of the International Thermonuclear
Experimental Reactor (ITER), developmental strategies for the demonstration fusion power plant (DEMO) are being
discussed. A relatively prudent strategy is to construct and operate a small deuterium–tritium fuelled volumetric
neutron source (VNS) in parallel with ITER. The VNS is to provide, over a period less than 20 years, a relatively high
fusion neutron fluence of 6 MW year m 2 and wall loading of 1 MW m 2 or more, over an accessible blanket test
area of more than 10 m2. Such a VNS would complement ITER in testing, developing, and qualifying nuclear
technology components, materials, and their combinations for DEMO and future commercial power plants. The
effort of this study has established the potential of the spherical tokamak as a credible VNS concept that satisfies the
above requirements.